overheating 80 (1995 1HZ)

[Cammud]

Hi all,
Just wondering if anyone has any ideas for my 1995 80 series standard, non turbo desiel 1hz overheating? It only does it going up hills such as Ourimbah and mooney on F3 to Sydney. The temp gauge is almost on the red.
However, around town, at traffic lights etc the gauge is normal,in the middle. I have had the fan clutch and water pump replaced not to long ago. The truck has 345000k's on it.

Any info greatly appreciated,

Cheers,
Cameron.

[dakar61]

If you havent done this already, chuck out the thermostat and renew it with a genuine Toyota one. Also check on the origins of the fan clutch. I have heard lately that some of the non-genuine units are not up to the task. Toyota unit is exxy but works best. Were the symptoms present prior to or after water pump & fan clutch? If they have just presented was the cooling system completely flushed when the above parts were renewed? Some coolants, if mixed, will block the radiator core.

Hope this helps

[Cammud]

Thanks for your info dakar61.I will replace the thermostat with a genuine part and see what happens. These symptoms have just appeard recently. Im not sure if the cooling system was completely flushed when they did the pump, but maybs I should do that at the same time? They did however put a new batch of coolant in the old girl though.

Thanks again.

[Dave_STR]

Funny though that after the water pump was changed that it started over heating. The fan is attached to the water pump, I would be looking at the fan first.

[sniper]

Also check to make sure they used coolant and not tap water. Also try giving it a flush yourself. trust no one!!!

[marki]

If you suspect the thermo, rather than replacing it, just run it without a thermo and see if it makes a difference - thermo's for 1HZs are mighty expensive.

Or the radiator may be partially blocked. If that's the problem it won't be obvious. Could be worth pulling it out and getting it reconditioned. I had a similar problem with my Hilux.

[dakar61]

If you suspect the thermo, rather than replacing it, just run it without a thermo and see if it makes a difference - thermo's for 1HZs are mighty expensive.


So is a new 1HZ engine.

Running it without a thermostat could well make it run hotter.

[stretch60]

I'm having the same problem with my 1991 80 series non turbo, runs all day over here in the west on the hottest days with air con going flat chat but add the camper trailer and drive up any incline putting a slight load on the motor and it starts to head for the red zone. I suspect it is the radiator and will pull it out for a complete rodding and flush before towing the camper again.

Cheers Stretch

[marki]

So is a new 1HZ engine.

Running it without a thermostat could well make it run hotter.

No it can't. It'll run cooler. Perhaps you don't understand how a thermostat works.:confused:
All the thermostat does is provide a potential restriction to coolant flow. Its absence can't possibly make a motor run hotter.

[Cammud]

Hi all,
Thanks for all your info, its been bloody awesome. You guys have given me some great ideas to make a start on fixing the old girl.

Cheers,
Cam

[uwishuhadalandy]

My 80 was doing exactly the same thing, Try putting clutch oil in the hub of your clutch fan, mine was getting hot on hills etc.
Go to toyota its around 15-20 dollars for I think its 30 or 50 ml tube. Un-bolt the fan and remove, remove the fan from the hub, The phillips head screws are usually pretty tight so its advisable to use an impact driver.
keeping it facing up{so nothing falls out}. squeeze contents of tube in and re-assemble. You should have a positive resault.
If its still over heating i'd take it to the radiater shop.

cheers wazza

[dakar61]

No it can't. It'll run cooler. Perhaps you don't understand how a thermostat works.:confused:
All the thermostat does is provide a potential restriction to coolant flow. Its absence can't possibly make a motor run hotter.

WRONG mate. Its you that doesnt understand how a thermostat works in an engine coling system! Check your facts first.:(

Yes it does provide restriction to flow, but that is part of its job. If there isnt sufficient restriction (even when the thermostat is fully open) to flow, then the coolant doesnt remain in the radiator for sufficient time for the heat exchange to occur in the radiator. If you remove the thermostat completely then the cooling ability of the radiator is reduced and the overheating symptom could be exacerbated especially if the thermostat is not the cause of the problem. You could, if you had the time, remove the old thermostat and cut the valve assembly out amd refit the outer flange to provide some restriction in the system, this may help eliminate the thermostat as a cause. To me it seems like a lot of effort (do you know where the thermostat is in a 1HZ?) and based on hourly rate it would be cheaper to fit a new Toyota thermostat.

[Boy Scout]

Im with uwishuhadalandy, the clutch fan hub assembly is not working the way it should. I had same hassles replaced thermostat, flushed entire system, even replaced the whole radiator and still the same hassles. Took it to local 4wd shop and they put it on a dyno, they can replicate going up hills. Found the clutch fan not to be working to its fullest, replaced the fluid inside. Problem fixed. I think cost around $80.00 including the dyno run.

Hope this helps.
Paul

[HDJ105]

Yep, sounds like a fan clutch issue, classic symptoms.

Depending on type of clutch fitted, a cheapo aftermarket one could be already stuffed. They don't last as long as the genuine ones (~$400)!

[marki]

WRONG mate. Its you that doesnt understand how a thermostat works in an engine coling system! Check your facts first.:(

Yes it does provide restriction to flow, but that is part of its job. If there isnt sufficient restriction (even when the thermostat is fully open) to flow, then the coolant doesnt remain in the radiator for sufficient time for the heat exchange to occur in the radiator.

If the coolant is hot, the rate of heat transfer is independent of flow rate. The rate of heat transfer (in any system) is determined purely by the temperature gradient.

In fact, higher flow rate will promote greater heat transfer - localised cooling brought about by a long residence time in the heat sink (radiator) will result in a reduction in heat transfer (cooling rate) until the cooled liquid is moved on.

I'm not sure whether you are a mechanic, but you've fallen prey to a misconception about heat transfer that is quite common - when I was a kid I was told not to stir my porridge, as it would cool faster if I didn't. In fact, the truth was that only the surface would cool faster, as the same bit of porridge was allowed to cool further and further by exposure to the air. But the porridge inside, of course, experienced minimal cooling, and I could get the whole thing cooler faster by stirring it and maximising the temperature gradient.

Are you able to provide a specific example of where a vehicle has removed a thermostat and the temperature has increased?

To me it seems like a lot of effort (do you know where the thermostat is in a 1HZ?) Yes - and I know it's a bastard to get to, but the last aftermarket thermo I bought was $45 - I'd hate to think what a Toyota one was.

I in fact had this opposite problem on mine. The engine was running very cool - temp gauge barely got off the bottom mark. While I was having other work done I got the mech to look at the thermo. Sure enough, although it was in there, one of the seals was buggered and so coolant was just going straight past.

[dakar61]

If the coolant is hot, the rate of heat transfer is independent of flow rate. The rate of heat transfer (in any system) is determined purely by the temperature gradient.

In fact, higher flow rate will promote greater heat transfer - localised cooling brought about by a long residence time in the heat sink (radiator) will result in a reduction in heat transfer (cooling rate) until the cooled liquid is moved on.

I'm not sure whether you are a mechanic, but you've fallen prey to a misconception about heat transfer that is quite common - when I was a kid I was told not to stir my porridge, as it would cool faster if I didn't. In fact, the truth was that only the surface would cool faster, as the same bit of porridge was allowed to cool further and further by exposure to the air. But the porridge inside, of course, experienced minimal cooling, and I could get the whole thing cooler faster by stirring it and maximising the temperature gradient.

Are you able to provide a specific example of where a vehicle has removed a thermostat and the temperature has increased?

Yes - and I know it's a bastard to get to, but the last aftermarket thermo I bought was $45 - I'd hate to think what a Toyota one was.

I in fact had this opposite problem on mine. The engine was running very cool - temp gauge barely got off the bottom mark. While I was having other work done I got the mech to look at the thermo. Sure enough, although it was in there, one of the seals was buggered and so coolant was just going straight past.

Firstly, I am a diesel fitter with 26 years in the trade. Your credentials are??

2/ Engine coolant is not porridge. If you have been using porridge & it works for you then good.

3/ I agree heat transfer is dependant on flow rate, that is my point, too quick and there is not enough time for it to take place, too slow and the engine gets hot also. Also they rate of transfer is dependant on the ambient temp surounding the radiator, big differences=high transfer rates.

4/ Yes, I can give you a specific example and that is if the over-heating symptom previously mentioned is especially not caused by a faulty thermostat. Do you know exactly what is causing Cammud`s engine temp issues? Neither do I. That is why I dont agree with your advice to him.

5/ The undertemp problem in your 1HZ was caused by the thermostat leaking or stuck open. It was not because it wasnt there. Read my previous post.

[deano180]

sounds very much like a fan hub to me as well,as for the thermostat advice
dakar61 is right,removing a thermostat can in fact make an engine run hotter due to the reasons he mentioned(coolant flowing through radiator too fast for efficient heat transfer to take place).not always the case, but the thermostat is there for a couple of reasons.
if you have a genuine fan hub try replacing the oil in it,if you have a non gen item bite the bullet and replace it with a genuine job,never had any luck with non genuine ones,they either crap out early or don't work all that well.
the genuine items are costly but so is replacing cheapo non genuine ones more often.

[TonyH]

3/ I agree heat transfer is dependant on flow rate, that is my point, too quick and there is not enough time for it to take place, too slow and the engine gets hot also. Also they rate of transfer is dependant on the ambient temp surounding the radiator, big differences=high transfer rates.


This is a funny argument! I'm a refrigeration technician, and my job depends entirely on heat transfer, so there's the creds out the way....

The above statement has got me though. If the coolant moves too fast to drop it's temp in the radiator by any great margin, then does this also mean it's temp doesn't rise by any great margin when it passes through the block? I'd say yes!


BUT Since the coolant is moving faster, then even though the temp changes are less, would it not be able to still reject the same amount of heat ENERGY from the engine in the same amount of time, due to the faster flow rate?

I'd guess from my experience, the water pump wouldn't be able to deliver the sort of flow rates required to have a major effect on cooling efficiency, but am interested to hear other views.

The other thing to point out here, is that some vehicles use a bypass system, where the thermostat movement re-directs the water flow away from the radiator and back into the block when it's cold, but blocks the bypass flow when the engine is hot and requires cooling.

Don't know if the Tojo motor does this, but I do know a TD42 does, so if anyone was thinking of removing a thermostat from their 4.2 deisel Nissan to solve a cooling issue, it won't work, as their will be nothing to control how much coolant goes through the bypass and how much goes through the radiator, so it will flow through both, and cause high engine temps.

My head hurts,


Tony

[sniper]

Yep it wont hurt to check you vacious fan oil, also check/refit a new thermostat.

Don not run your truck without one. Doing that is a bandaid for emergancies. Always run a thermostat.

Flush your cooling system.

There goes one day in your weekend but at least you spent it on your pride and joy + you will be drinking beer ;)

This way your cooling system should be mickey mouse (provivng your radiator isnt clogged).

[dakar61]

The Toyota thermostat has a bypass valve also.

Let me simplify this argument.
Remove the radiator and replace it with a piece of exhaust tube 6" in diameter.
Remove the thermostat also.
Very low restriction to flow now.
Coolant should be travelling very quickly.
An efficient device to transfer heat from the coolant to the atmosphere?
I dont think so.
Time and surface contact area are what is required for the heat transfer to take place from coolant to surroundings.

[marki]

Firstly, I am a diesel fitter with 26 years in the trade. Your credentials are??



Chemical engineer with many years experience. When designing chemical processes that generate (chemical) heat, and knowing that certain components of a system only have a certain heat tolerance, heat transfer and cooling considerations occupied me more than any other issue.

There was one process that had a very tight production schedule, and the #1 factor in meeting the schedule was the rate at which I could get the 20,000 L batch to cool. If I didn't get it down to temp before the truck arrived, we were in the sh1t. The cooling system that I designed managed to speed up the process and increase our production schedule.

Whether porridge, or coffee, or chemical systems, or fridges, or engines, heat transfer dynamics all follow the same rules. I'm afraid I don't have time to respond to all your points, but trust me - you don't understand heat transfer. Pick any engine you like under any circumstances you like and remove the thermostat - the temp will drop. No other outcome is possible.

The above statement has got me though. If the coolant moves too fast to drop it's temp in the radiator by any great margin, then does this also mean it's temp doesn't rise by any great margin when it passes through the block? I'd say yes!

Quite right. Good point.

[dakar61]

The laws of thermodynamics are constant. But the situations to which they are applied vary and therefore so do the outcomes.

I`ll agree to disagree with you.

As Homer`s brain said to his body " Right, I`m outta here"

[Peter @ Aawen4x4]

The above statement has got me though. If the coolant moves too fast to drop it's temp in the radiator by any great margin, then does this also mean it's temp doesn't rise by any great margin when it passes through the block? I'd say yes!


In my experience you are right; but regardless of where the coolant does or doesn't pick up or lose heat, the ENGINE as it is operating generates heat and requires cooling!! So in this particular case, the fact that the coolant is moving too fast to absorb or radiate temp from/to anything doesn't stop the block getting hot and therefore it STILL results in the ENGINE overheating and ultimately dieing!

So by taking out the Thermostat, you CAN cause the ENGINE to overheat and die! And it DOES happen!! :mad:

[stretch60]

Is there a simple way to check the fan clutch, been driving around today (40c and humid) and the temp gauge hasn't moved from half way, as I said last post it only seems to happen when towing the camper up gradients, and it isn't that heavy.

[Peter @ Aawen4x4]

The simplest method is to leave the engine running and open the bonnet after a drive, then as you turn off the engine, watch what the fan does. If the fan stops pretty much straight away, then it should be working! If it free-wheels on for more than 1 revolution or so, then it isn't working!

Other signs that it isn't working?! Before you start the car in the morning, try turning the fan by hand. You shouldn't be able to get it to spin freely, it should turn only when pushed; stop pushing it should stop turning straight away! Then when you start the car, the fan should be engaged for a second or two, and you should be able to hear it and feel the air being forced out. As the car settles to running, the fan noise should lessen and the fan should actually slow to less than engine revs. Yeah, hard to tell that unless you want to stick your hand in the fan and stop it, and that's not something you should do unless you KNOW that it will be freewheeling!! If it is freewheeling, your hand will easily stop the fan, but be VERY CAREFUL if you try!

When you are driving/towing, and the temp starts to go up, you should be able to HEAR the roar of the fan clutch tightening up and cutting in. If you don't hear it roar, there is a very good likelihood that the fan clutch isn't working properly! Apart from that, you can try starting the car from cold while someone is HOLDING the fan stopped! Keep someone holding it, and you watch the temp. When the temp gets above normal (maybe 10 mins should do it) let the fan go! If it doesn't pull the temp back to normal very quickly, and you can't hear it roaring or feel the blast of air coming out of the fan shroud area, then your fan clutch isn't working properly!

And be a little careful if you start adding silicone to the fan hub - too much is almost as bad as not enough, in that it will keep the fan running ALL the time, sapping power and dragging the temp lower than optimum SOME of the time if not all the time!

Enjoy!

[Cammud]

Hi all,
Yeh mine is the same as yours stretch60. hasnt moved from the middle but i know when i go to work from Newcastle to Sydney tomoz, she'll hit the red on the hills.

Little bit more info as well. I had the fan clutch replaced 72000k's ago on the 02/06/06 at natrad Newcastle. The water pump was done 25000k's ago on the 16/05/07.

After reading all the very interesting and useful comments (thanks heaps guys) i checked the fan clutch and it seems to have a bit of movement in it.By that I mean if I grab a top and bottom fan blade the whole thing moves on the drive stem? They actualy call this thing a fluid coupling, amazing what you find out when you actualy read the workshop book! As well it has traces of oil or black dirt on it in certain parts.

Hang on a minute though, the fan clutch and the fluid coupling is the same thing is'nt it????

So im going to replace the thermostat (genuine one) and flush radiator and system on my next days off next week and see what happens. If that does'nt work then maybs replace the fan clutch (fluid coupling) with a genuine one?

But once again thanks all,
glad i could also spark an interesting debate!

Cammud.

ps.I will keep you all informed of the progress.

[Zig]

Hi all,
Yeh mine is the same as yours stretch60. hasnt moved from the middle but i know when i go to work from Newcastle to Sydney tomoz, she'll hit the red on the hills.

Little bit more info as well. I had the fan clutch replaced 72000k's ago on the 02/06/06 at natrad Newcastle. The water pump was done 25000k's ago on the 16/05/07.

After reading all the very interesting and useful comments (thanks heaps guys) i checked the fan clutch and it seems to have a bit of movement in it.By that I mean if I grab a top and bottom fan blade the whole thing moves on the drive stem? They actualy call this thing a fluid coupling, amazing what you find out when you actualy read the workshop book! As well it has traces of oil or black dirt on it in certain parts.

Hang on a minute though, the fan clutch and the fluid coupling is the same thing is'nt it????

So im going to replace the thermostat (genuine one) and flush radiator and system on my next days off next week and see what happens. If that does'nt work then maybs replace the fan clutch (fluid coupling) with a genuine one?

But once again thanks all,
glad i could also spark an interesting debate!

Cammud.

ps.I will keep you all informed of the progress.

Mine is like that too. It's a std. 1HZ with a Safari turbo and intercooler. Run all day long in soft sand on a hot day, but with the camper trailer (750kg) on a hot day (35-40) it starts to run a bit warm if you drive "fast" i.e. above 120km/h or on hills.
I replaced the thermostat with a genuin, flushed the radiator, new non genuin fan clutch.... no change. I then fitted a 3 inch straight through exhaust. That made it a lot better but I have still had times when the needle started going up. I pulled the Lightforce 240's off one hot day when I was towing the camper and the engine temp was up, but it made no difference.
I'm now thinking about a new radiator. I need to solve this problem as I am taking the camper in to the Red Center in October this year.

[Peter @ Aawen4x4]

Mine is like that too. It's a std. 1Hz wit a Safari turbo and intercooler. Run all day long in soft sand on a hot day, but with the camper trailer (750kg) on a hot day (35-40) it starts to run a bit warm if you drive "fast" i.e. above 120km/h or on hills.
I replaced the thermostat with a genuin, flushed the radiator, new non genuin fan clutch.... no change. I then fitted a 3 inch straight through exhaust. That made it a lot better but I have still had times when the needle started going up. I pulled the Lightforce 240's off one hot day when I was towing the camper and the engine temp was up, but it made no difference.
I'm now thinking about a new radiator. I need to solve this problem as I am taking the camper in to the Red Center in October this year.

If your radiator has been professionally serviced, then I wouldn't be replacing it! More than likely your problem is just a tolerance issue, in that when the EGT starts getting high, there just isn't enough 'spare' cooling capacity in your system to keep it all cool! Do you run a Pyrometer?? That'd show you what's going on when (and why) it gets hot, and you might be able to change your driving style to suit!

BUT, really there are two things that each will be almost certainly able to resolve this overheating! The first one - turn your fuel down a little - maybe even as much as a 1/4 turn on the nut, probly only 1/8th will do it tho! Yes, you MIGHT lose a little power, but because diesels get hotter the more fuel you put in, cutting the fuel back also makes them run cooler! The second one is to replace the radiator with a much larger capacity aluminium triple flow custom cooler - Desert Coolers do them I think! These things massively increase the capacity and cooling ability of your cooling system and MASSIVELY deplete the contents of your wallet for a long time! They LOOK great and work well, but you can achieve the same thing with 10 mins work with a spanner?!! I'd go the first option!

Oh, and there probly is a third option too - increase the cooling capacity of the intercooler. Maybe not so definitely a cure, but it might help!

Cheers!

[Zig]

Thanks Peter!
No I don't run a pyrometer/EGT guage yet. It is on the shopping list.

[TonyH]

Pick any engine you like under any circumstances you like and remove the thermostat - the temp will drop. No other outcome is possible.

Unless it runs a bypass cooling system... :p

Be careful not to make this mistake!

[s1mon]

make sure you use the red coolant from toyota as well

[crawla]

not to get too involved here but an example in dakar61s case relates to the 6.5 chev diesel. The later motors ran with 130gpm water pumps running twin high flow thermostats. This was fine on a silverado because the radiators were massive and were able to cool the water even with such a high flow system.

A few motors were running on the warm side when put in other vehicles for conversions. The motor had all the right gear but the radiator was too small for the cooling system. The water was running through that fast the radiator wasn't big enough to cool things.

In regards to the fan hub I'm with Deano all the way. I would pay the extra and get a genuine one.

[CCoast Phil]

make sure you use the red coolant from toyota as well
Is this coolant better than the Green stuff?

[MudChaser]

To check the operation of your thermostat place it in an open saucepan full of water on the stove and heat the water. Look on the side of the thermostat and the temperture should be stamped on it at what temperature the thermostat starts to open and if you have a thermometer that reads too 100 degrees C. place it in the saucepan and watch what temperature the valve starts to open. If the valve opens then the thermostat is working. It`s a bit of mucking around and you don`t have to do the thermometer thing if you don`t want to.
Also the other possibility is that the water pump may have the wrong gasket fitted and is restricting the flow.
Could also be a fault in your temperature sender unit giving you a false reading.

[s1mon]

Is this coolant better than the Green stuff?

I recon it is, I think there is some toyota engines, that if you put normal green coolant in them they are more likly to crack a head early in there life, not sure if this is the case for the 1HZ though, I just use it anyway, even in my patrols

[marki]

In my experience you are right; but regardless of where the coolant does or doesn't pick up or lose heat, the ENGINE as it is operating generates heat and requires cooling!! So in this particular case, the fact that the coolant is moving too fast to absorb or radiate temp from/to anything doesn't stop the block getting hot and therefore it STILL results in the ENGINE overheating and ultimately dieing!

So by taking out the Thermostat, you CAN cause the ENGINE to overheat and die! And it DOES happen!! :mad:

Peter, with respect, this is wrong in so many ways, I don't know where to begin.

If fast moving coolant could not absorb or radiate heat, you'd get the situation where a motor could overheat while a completely full coolant system, circulating without a thermostat, was not even warm. And since the temp gauge measures coolant temperature, you're telling us that it'd overheat without the temp gauge ever getting into the red zone. You don't really believe that do you?

Also, what do you think cools faster - an air cooled m/c engine that is moving (has abundant cool air flowing over it) or one that is stationary (no air flowing over it)?

[dakar61]

Is this coolant better than the Green stuff?

The red Toyota coolant is generally for use in their alloy headed, alloy radiator vehicles. It is also supposed to be long life i.e up to 150,000km. Just check with a reputable coolant manfacturer or the OEM for their recommendations. We use Nulon Long Life Green for the majority of the cast iron, copper radiator core engines.

[Minty97GXL]

I have a temp problem of a different nature. When towing the caravan with the A/C running, the A/C will cut out and start to blow warm air. This happens after driving around 25 klm's on a hot day. Any other time with it running and it runs all day without the van on, so I'm thinking it is something to do with the settings of the A/C in relation to the load being towed. Temp gauge doesn't even get up to halfway with the van on, but it does go up. One bit of bad advice I was given was to disconnect some wire under the bonnet, but we don't want a icebox inside the cabin.
Any ideas on the problem at all? A sensor maybe or just a setting problem?
I know should get to a A/C garage to have it checked out, but don't use it when working and finishing at 6pm makes it hard to even get to one.

[cruza driver]

To check the operation of your thermostat place it in an open saucepan full of water on the stove and heat the water. Look on the side of the thermostat and the temperture should be stamped on it at what temperature the thermostat starts to open and if you have a thermometer that reads too 100 degrees C. place it in the saucepan and watch what temperature the valve starts to open. If the valve opens then the thermostat is working. It`s a bit of mucking around and you don`t have to do the thermometer thing if you don`t want to.
Also the other possibility is that the water pump may have the wrong gasket fitted and is restricting the flow.
Could also be a fault in your temperature sender unit giving you a false reading.
If doing this and it does open at the correct temp also make sure it opens fully so coolant flow isn't restricted.
By reading the symptoms I would lean towards radiator as it seems to be overheating when the engine is underload ie; towing or goin up hill.
I would get a professional radiator flush (remove tanks) and see if the core is blocked. Also check that the radiator fins aren't blocked and also check between the A/c condensor and radiator that air flow isn't restricted (mud,grass,leaves etc)
good luck with it

[FourXfouR]

There are correct claims by each arguing party. However I am going to simplify it in this one statement.

Removing a Thermostat ALTOGETHER ( not leaving the restriction ring in place ) MAY NOT cause the temperature GAUGE to rise but it can, has and probably WILL cause the temperture of the engine block and cylinder head to rise

Anyways it sounds to me like your clutch fan in not operating correctly

[FourXfouR]

I have a temp problem of a different nature. When towing the caravan with the A/C running, the A/C will cut out and start to blow warm air. This happens after driving around 25 klm's on a hot day. Any other time with it running and it runs all day without the van on, so I'm thinking it is something to do with the settings of the A/C in relation to the load being towed. Temp gauge doesn't even get up to halfway with the van on, but it does go up. One bit of bad advice I was given was to disconnect some wire under the bonnet, but we don't want a icebox inside the cabin.
Any ideas on the problem at all? A sensor maybe or just a setting problem?
I know should get to a A/C garage to have it checked out, but don't use it when working and finishing at 6pm makes it hard to even get to one.

Without actually looking at the truck its hard to say, but I would actually check the operation of your clutch fan. High side (condenser) pressures can be influenced by a higher radiator temp and lack of airflow across the condenser fins. Once this pressure reaches a pre-determined level, the High pressure switch will cut power to the clutch coiland not engage until the high side pressures have stabilised. Failing that, get the system checked for an overcharge and maybe consider fitting a condensor fan from the VX models

[Minty97GXL]

Without actually looking at the truck its hard to say, but I would actually check the operation of your clutch fan. High side (condenser) pressures can be influenced by a higher radiator temp and lack of airflow across the condenser fins. Once this pressure reaches a pre-determined level, the High pressure switch will cut power to the clutch coiland not engage until the high side pressures have stabilised. Failing that, get the system checked for an overcharge and maybe consider fitting a condensor fan from the VX models

Thanks for the reply, will keep this info for when I do get it to be checked out.

[Reedy]

I agree about the clutch fan but just a long shot have you wound the fuel up on your Deisel pump??? That will make your engine temp rise if it is being over fueled especially when you are flooring it up long steep climbs!!! Also how is your timing on your Diesel pump???:confused:


Reedy!!!:thumb:

[slack]

Interesting arguments guys. I had a similar problem with my HDT. Turns out that after a mud run I hadn't cleared all the mud out. 30% blocked. Could your problem be that simple?

[marki]

Removing a Thermostat ALTOGETHER ( not leaving the restriction ring in place ) MAY NOT cause the temperature GAUGE to rise but it can, has and probably WILL cause the temperture of the engine block and cylinder head to rise


How? What are you saying - the engine block gets hot but the coolant doesn't? You don't really believe that do you?

not to get too involved here but an example in dakar61s case relates to the 6.5 chev diesel. The later motors ran with 130gpm water pumps running twin high flow thermostats. This was fine on a silverado because the radiators were massive and were able to cool the water even with such a high flow system.

A few motors were running on the warm side when put in other vehicles for conversions. The motor had all the right gear but the radiator was too small for the cooling system. The water was running through that fast the radiator wasn't big enough to cool things.

Did you try a different flow rate (slower or faster)? If you'd put a higher flow pump in, the overheating problem would be less. It sounds like the radiator was just too small.

The laws of thermodynamics are constant. But the situations to which they are applied vary and therefore so do the outcomes.

Unfortunately, thermodynamics don't apply in this case - thermodynamics only apply, by definition, to systems at equilibrium. This issue is involved with the kinetics of heat transfer - a nonequilibrium system.

It's the end of the week, and the Mrs is interstate, so I'll take a bit of time to explain heat transfer principles.

Firstly, if it is true that fast moving coolant doesn't transfer heat, then the following are true:

1. Air cooled motorcycles would overheat at high speeds.

2. Cooling fans wouldn't exist. Whether it's the fan in your lounge room, or the fan on your radiator, their function is to provide a high flow of coolant (air) past the heated surface to facilitate heat transfer.

3. If you hopped in your shower and turned the cold water on fast enough, it wouldn't feel cold, as there would be no heat transfer between the water and your skin.

4. Engines could overheat without the coolant getting hot.

So you can see that the idea of coolant moving too fast to transfer heat is ridiculous.

But if you haven't thought it through, I understand why people think this way. You imagine a molecule of water wizzing through a radiator quickly, and think "how could it have transferred any heat? It was moving too fast."

Right?

Well, that part is true - but there's another factor that you haven't considered:

Imagine the following system:

Coolant volume: 10L
Flow rate: 1L/min
Initial temp: 100 deg

Suppose that we run this system for 1 minute and the water that initially comes in one side of the radiator at 100 deg has cooled to 95 deg when it leaves.

We now increase the flow rate through the system to 5L/min - so 5 times as much coolant flows through in the same time period.

Q: What sort of temperature drop will we see if the cooling rate is exactly the same?

A: 1 degree

In other words, if 1 molecule loses 5 degrees, the system has lost exactly the same amount of heat if 5 molecules each lose 1 degree.

Now, here's the point: rate of heat transfer is proportional to the temperature difference with its surroundings. In other words, hotter liquids lose heat faster than cooler systems.

For example, if you poor boiling water into a coffee cup, put a thermometer in it, and measure the time it takes to cool from 90 to 80, you will find it is a shorter time period than the time taken from 80 to 70.

This means that water at 100 deg loses heat at a greater rate than water at 99, 98, 97, 96 or 95 deg.

So in the high flow system we are considering, the water will have lost more than 1 degree in temp. Suppose it loses 1.5 deg.

Heat calculations are:

Low flow: 1L x 5deg = 5 KCal heat lost

High flow: 5L x 1.5deg = 7.5 KCal heat lost

Consider the temperatures. Once the water has passed through the radiator, it will of course, mix in with the rest of the (hotter) water and the temperature will average out.

In our example:

low flow: (100x.9 + 95x.1) = 99.5 deg
high flow: (100x.5 + 98.5x.5) = 99.25 deg

Thus, it can be seen that increased flow rate results in greater heat loss.

The argument is, of course, exactly the same for the case of water being heated - the same principles apply.

There are many more principles that I could discuss, with specific industrial examples, but I don't want to confuse the issue. In any case, if you still don't understand, then you probably never will.

If you want to increase the cooling capacity of the system in your car, therefore, your options are:

1. Bigger heat exchanger (radiator)
2. Greater volume of coolant (heat is lost from all parts where the coolant contacts metal or hose)
3. More powerful fan
4. Greater flow of coolant through the system

Note: The principles in points 3 and 4 are exactly the same. The increased air flow results in a higher rate of flow of coolant past the heated surface, and therefore maximised cooling by maximisiing the temperature difference between the hot and cool surfaces.

Right - that's it. If you still don't understand heat transfer, and you spend thousands on a new radiator when you could've solved it with a more powerful pump, don't say I didn't try to help.

Good luck guys :thumb:

[stretch60]

Crawla, my mate put a 6.5 in his scout and has had all sorts of dramas with cooling the beast inside.

Stretch

[nilla60]

years ago someone from work had an 80 that would chronically overheat when driven hard "out bush" but behaved perfectly 'round town. After lots and lots of trying things out, they were not able to solve the problem and traded the vehicle and got another one. The EGT thing is the most prospective thing I bet this person at work never looked at. So I'd suggest checking the usual cooling isssues (take your vehicle to a good radiator place, they get to know what makes different vehicles tick), then look at tweaking back the juice (even temporarily) to see if it's an EGT issue. If that doesn't work, you knows there's at least one other 80 out there with persistant overheating problems.

[crawla]

Crawla, my mate put a 6.5 in his scout and has had all sorts of dramas with cooling the beast inside.

Stretch

no disrespect stretch but why??? click onto the weather for the pilbara WA and see what temps we are getting here, roebourne would be good to go off for us. Check out the weather for Tom Price also. I run a 6.5 turbo so the turbo would be putting more stress on the motor, you didn't mention a turbo on your mates so he is in front already. We have seen and will see consistent temps over 40 for who knows how long till the dry season approaches. If I and the others I know (80s and GUs) have no heating issues in these temps why would your mate have issues in his scout?

Yesterday for example I ran mine into town and back (100km round trip), it would have had to have been close to 40 or over and she ran at 88-90 degrees the entire time (between 88-92 is correct). She may be lighter than an 80/GU but my aerodynamics are crap and I run a full size insect screen on the bull bar.

I have a rediculously big custom 4 row 16mm tubing alloy radiator but the mates with the GU and 80s are running nothing special and they have no dramas either.

Crikeys marki!!! That is a response. You obviously sound knowledgeable on the topic, on the various forums I have read, on more than one account blokes have put in normal thermostats to slow down the flow which have apparently worked for them............I'll sort em' out now:D To me it made sense but if there is more to it than that I am not going to argue.......interesting read to say the least. As for your 4 points at the end I will agree there. With a huge radiator, 12 blade fan, 30+L of coolant and a 130gpm system I have no cooling issues. cheers

cheers

[dakar61]

quote<So you can see that the idea of coolant moving too fast to transfer heat is ridiculous.>unquote


In your considerable efforts to educate us, my learned friend, you have missed one very important point and that is;

IN THIS SYSTEM THE COOLANT NEEDS TIME IN THE RADIATOR FOR THE HEAT TRANSFER TO OCCUR. REMOVE THE THERMOSTAT WHICH NOT ONLY CONTROLS THE TEMPERATURE BUT ALSO THE RATE OF FLOW THRUOGH THE RADIATOR AND THIS ENGINE AND MOST OTHERS WITH THIS TYPE OF COOLING SYSTEM WILL OVERHEAT

ABSOLUTE FACT.

quote<Right - that's it. If you still don't understand heat transfer, and you spend thousands on a new radiator when you could've solved it with a more powerful pump, don't say I didn't try to help.>unquote

And now you want to re-invent this poor blokes cooling system by installing a bigger pump when in your first post you were worried about the price of a lousy thermostat.:confused: :confused:

BTW, if someone quoted you "thousands" for a new radiator and you believed them, well, I`ve got a bridge in Sydney you might be interested in......:crazy: :crazy:

[crawla]

LOL...without getting involved again............why do they have triple flow radiators??

[uwishuhadalandy]

Faaark are you blokes still gionG???

[Reedy]

God just build a bridge and get over it!!!! Just give your advise and move on fella's, I don't think anyone will win this arguement!!!:crazy:

[marki]

IN THIS SYSTEM THE COOLANT NEEDS TIME IN THE RADIATOR FOR THE HEAT TRANSFER TO OCCUR. REMOVE THE THERMOSTAT WHICH NOT ONLY CONTROLS THE TEMPERATURE BUT ALSO THE RATE OF FLOW THRUOGH THE RADIATOR AND THIS ENGINE AND MOST OTHERS WITH THIS TYPE OF COOLING SYSTEM WILL OVERHEAT

ABSOLUTE FACT.



Really?

So you are saying that an engine can overheat without the coolant ever getting hot?

[Reedy]

Still going!!!:crazy: :zzz:

[dakar61]

Still going!!!:crazy: :zzz:

Nope.

I`m calling it.

You can be right, marki, if you need to be.
Hopefully now we can all have some peace.............:drink:

My apologies to those of you who felt we dominated the post with the argument.

I`ll know better next time....

[Cammud]

Hi all,
Just wanted to let you all know that I changed the fan clutch (fluid coupling), took the truck out for a test run on the hills where she gets hot and all is good. The temp gauge remained right in the middle (normal ) spot. I had the a/c on full, it was a fairly warm day and she charged up the hill no probs.
The replacement fan clutch is a non-genuine one, cost $175.00. Toyota quoted $547.00 for genuine but I just wanted to see if that was the problem first before spending that much, which at this stage looks like it was. I may go genuine when this one lets go???
Anyway thanks all for your help and info as well as making this topic a very interesting debate.
Cheers Cammud.

[marki]

Nope.

I`m calling it.

You can be right, marki, if you need to be.


Actually, all I did was ask you a question. I find questions are good ways to learn things from people that know more than you do.

And you obviously know more about cooling systems than I do, since you assure us that it is an ABSOLUTE FACT that running an engine without a thermostat will cause it to overheat.

So for my benefit (and others on this blog who'd like to understand the influence of a thermostat on a cooling system), can you please help me understand it?

A good place to start is the question that I asked you before - are you saying that an engine without a thermostat will overheat without the coolant ever getting hot (as it is circulating too fast)?

[dakar61]

Actually, all I did was ask you a question. I find questions are good ways to learn things from people that know more than you do.

And you obviously know more about cooling systems than I do, since you assure us that it is an ABSOLUTE FACT that running an engine without a thermostat will cause it to overheat.

So for my benefit (and others on this blog who'd like to understand the influence of a thermostat on a cooling system), can you please help me understand it?

A good place to start is the question that I asked you before - are you saying that an engine without a thermostat will overheat without the coolant ever getting hot (as it is circulating too fast)?

Too late to act the innocent bud.

Myself and others probably more qualified than you or I tried to explain it to you but all you were more interested in doing a Good Will Hunting impression than taking good advice.

Trust me, if I wanted advice on how to cool 20,000 litres of porridge for Goldilocks and the Three Bears, real quick, I would call you, no risk, but you don`t understand engine cooling systems.

Now get a life and drop it.

[FourXfouR]

Trust me, if I wanted advice on how to cool 20,000 litres of porridge for Goldilocks and the Three Bears, real quick, I would call you.

I have to say........

BWAHAHAHAHAHAHAHAHAHAHAHA! thats hilarious!

[TonyH]

PM's are a good place for that sort of stuff.....

Anyhoo, my 1972 Deluxe Hub Shift 3 speed Malvern Start has NEVER had an over heating problem! hehe


More seriously, if I can hear my fan speed up and slow down, does it mean it's okay, or can it appear to work and still be lazy?

[Peter @ Aawen4x4]

TonyH, yes it can!

Some of the silicone in the fan hub can leak out or even lose it's ability to work properly if it gets burnt or overheated too often! So as your fan loses silicone, your fan CAN appear to work but still not be doing it's job! It isn't too hard to check its function, tho! That's 'cos it does lose 'tightness' as it gets weaker, and that means that when you shut down the engine, it will spin on a little, and when you start to get warm on a longish climb, it won't get to spin as 'hard' and the roar will be lesser than normal. The temp will generally start to climb a little before the fan cuts in, or take longer to cool down after getting hot!

Worth checking with a laser thermometer if you are not able to decide for yourself that it's not working at its best!

Cheers!

[TonyH]

Cool, thanks Pete. I mjight just replace the silicon anyways. Can't hurt even if it's not the problem. (I reckon I may be running a smidge too rich, but my cooling system is due for a service, and I'm gonna get the beast dyno'd soon)




So for my benefit (and others on this blog who'd like to understand the influence of a thermostat on a cooling system), can you please help me understand it?

A good place to start is the question that I asked you before - are you saying that an engine without a thermostat will overheat without the coolant ever getting hot (as it is circulating too fast)?

In theory maybe... In practice that claim is a load of bull!!!

Yes, a bypass system without a T-Stat will probly overheat (in this system the thermostat moves according to it's heat. It moves a plate which directs more water through the radiator when the coolant temp rises, and when the coolant temp is low, the thermostat moves in the opposite direction blocking the radiator path and allowing more coolant to bypass the radiator and go straight back into the block to increase it's temp quicker.)

NO, a normal system will not overheat without a thermostat. There may be isolated cases where this is not true, but generally it is. You can do all the maths you want, but growing up in central Qld with shitbox Commodores and old Datto 120 Y's etc, it's fairly common to have to pull the thermostat out to keep things cool on a long HOT country trip in the middle of nowhere. Mainly when the radiator fins are shagged and it can't handle the heat anymore. I'd say that the extra flow actually HELPS cooling!! How else can it overcome an innefficient radiator?

To any engineer who may disagree, these are case studies, not hypothesies. Both my 120 y's got subject to this treatment as did my first Commodore. They were all NON bypass systems. These were all temporary repairs til a new thermostat and radiator could be fitted.

As I said in earlier posts, a bypass system will probly not benfit from thermostat removal, and will probly struggle/fail to keep the engine temp at acceptable levels. You can cut the disc out of the top of the thermostat and leave the bottom smaller disc in place (this is the one that blocks the bypass path) which will help get you out of trouble if you have a dodgy thermostat or the radiator is marginally failing to help. It's a temporary bush repair!

A non bypass system will always benefit from thermostat removal IF the radiator is struglling due to innefficiency or the the thermostat is knackered. If the radiator is shagged troo much, nothing will help.

How do you tell if your system is a bypass or normal type system?

A normal system has one large disc.

A bypass system has one large disc, one small disc and is around twice the length of a standard one.

Sorry if this upsets any engineers etc, but this is my experience!

To anyone else, hope it helps.:thumb:

[marki]

Yes, a bypass system without a T-Stat will probly overheat (in this system the thermostat moves according to it's heat. It moves a plate which directs more water through the radiator when the coolant temp rises, and when the coolant temp is low, the thermostat moves in the opposite direction blocking the radiator path and allowing more coolant to bypass the radiator and go straight back into the block to increase it's temp quicker.)

NO, a normal system will not overheat without a thermostat. There may be isolated cases where this is not true, but generally it is. You can do all the maths you want, but growing up in central Qld with shitbox Commodores and old Datto 120 Y's etc, it's fairly common to have to pull the thermostat out to keep things cool on a long HOT country trip in the middle of nowhere. Mainly when the radiator fins are shagged and it can't handle the heat anymore. I'd say that the extra flow actually HELPS cooling!! How else can it overcome an innefficient radiator?

To any engineer who may disagree, these are case studies, not hypothesies. Both my 120 y's got subject to this treatment as did my first Commodore. They were all NON bypass systems. These were all temporary repairs til a new thermostat and radiator could be fitted.

As I said in earlier posts, a bypass system will probly not benfit from thermostat removal, and will probly struggle/fail to keep the engine temp at acceptable levels. You can cut the disc out of the top of the thermostat and leave the bottom smaller disc in place (this is the one that blocks the bypass path) which will help get you out of trouble if you have a dodgy thermostat or the radiator is marginally failing to help. It's a temporary bush repair!

A non bypass system will always benefit from thermostat removal IF the radiator is struglling due to innefficiency or the the thermostat is knackered. If the radiator is shagged troo much, nothing will help.


Thanks for the explanation - it's a shame that other people were not able to provide it.

From your description, it sounds as tho my 1HZ has a bypass system.

But it raises the question of why bypass systems exist. Normal systems hold the coolant in the block until it reaches a certain temp, and then release it - so if you're in the middle of nowhere and your thermo sticks shut, all you have to do is pull it out and away you go.

If, in a bypass system, the radiator is dependant on a functioning thermostat to get sufficient coolant through it, exactly what advantage does a bypass system have over the normal one? Me no unnerstan'

[marki]

Too late to act the innocent bud.

Myself and others probably more qualified than you or I tried to explain it to you but all you were more interested in doing a Good Will Hunting impression than taking good advice.

Trust me, if I wanted advice on how to cool 20,000 litres of porridge for Goldilocks and the Three Bears, real quick, I would call you, no risk, but you don`t understand engine cooling systems.

Now get a life and drop it.

No, I am asking for advice now. You tell us that you are highly qualified answering questions should be easy for you then, shouldn't it?

You say that coolant needs "residence time" to transfer heat. Does this mean that without a thermostat an engine will overheat without the coolant ever getting hot?

I suspect that the reason that you won't answer this question (for the 4th time) is that you realize that it exposes the error of your argument.

I'm trying to help you out here mate. You just make a fool of yourself when you post childish insults in response to a straightforward question.

TonyH says:

As I said in earlier posts, a bypass system will probly not benfit from thermostat removal, and will probly struggle/fail to keep the engine temp at acceptable levels. You can cut the disc out of the top of the thermostat and leave the bottom smaller disc in place (this is the one that blocks the bypass path) which will help get you out of trouble if you have a dodgy thermostat or the radiator is marginally failing to help. It's a temporary bush repair!

Tony - have you ever actually had to do this? I'm trying to understand the implications of your use of "probably".

My 1HZ was running too cool recently. The mech said that it did have a thermostat, but the seal had ruptured.

Now, although I understand what you say about the possibility of coolant bypasssing the radiator, surely if a ruptured seal results in overcooling, then an absent thermo will result in even more cooling (altho I'd have to sit down and have a look at a schematic of the fluidics before I'd be absolutely confident about that).

It's just that it seems to me that from an engineering standpoint, Toyota would be pretty dumb if they hadn't built redundancy into the system (by the design of the bypass channels), so that an absent thermo would still allow the motor to run without o/heating.

[TonyH]

Yeah dude, I tried it once, in an effort to cool down my old Wagon. The temp problem got even worse!


I can only say probably, because the one time I removed my T/Stat was trying to cool an engine that I eventually realised had a slight head gasket leak. So in normal circumstances I don't have personal experience. My good mate however is a top mechanic, and put me onto the removing the big disc from the T/Stat of a bypass system, which has worked for him in the past.



The seal you talk about would have had to have been letting more coolant through the radiator, causing extra cooling. How on earth can your engine run cooler if the coolant bypasses the radiator and feeds straight back into the block?

Your last statement made me giggle a bit. Why would Toyota design a motor that would be able to run without a T/Stat? Thats a bit like saying it should be able to run without a belt driving the water pump, no?I


can qualify "probly" by relating back to non bypass systems that have benefitted from thermostat removal. Also, by nature of hydraulics, and the path of least resistance etc etc, the majority of coolant would still go through the radiator, as the by-pass loop has smaller pipes to run through. But as the smaller amountof water goes straight back into the block to be reheated again without any cololing, it will place a large strain on your system. You're an engineer, try to visualise it by drawing a picture or something, and it will be quite clear once the penny drops :thumb:

[dakar61]

"I'm trying to help you out here mate. You just make a fool of yourself when you post childish insults in response to a straightforward question."

Yep, sorry mate, about the insults.

I still stick by my advice though.

As for the question, I dont see that it is relevant in the case of the 1HZ recirculating cooling system.

Jump on the net and do some research about diesel cooling systems, you`ll find that the thermostat is a very important part of the system and there for some very good reasons, such as prevention of localised hotspots (when the rest of system seems cool), the prevention cavitation erosion, the prevention of premature engine wear, the prevention of engine emissions etc. You cant just ditch it arbitrarily.

Check it out.. Or I`ll jump through yer speakers and rip yer bluddy arms orf !!!:D

[marki]

Yeah dude, I tried it once, in an effort to cool down my old Wagon. The temp problem got even worse!


I can only say probably, because the one time I removed my T/Stat was trying to cool an engine that I eventually realised had a slight head gasket leak. So in normal circumstances I don't have personal experience. My good mate however is a top mechanic, and put me onto the removing the big disc from the T/Stat of a bypass system, which has worked for him in the past.



The seal you talk about would have had to have been letting more coolant through the radiator, causing extra cooling. How on earth can your engine run cooler if the coolant bypasses the radiator and feeds straight back into the block?

Your last statement made me giggle a bit. Why would Toyota design a motor that would be able to run without a T/Stat? Thats a bit like saying it should be able to run without a belt driving the water pump, no?I


can qualify "probly" by relating back to non bypass systems that have benefitted from thermostat removal. Also, by nature of hydraulics, and the path of least resistance etc etc, the majority of coolant would still go through the radiator, as the by-pass loop has smaller pipes to run through. But as the smaller amountof water goes straight back into the block to be reheated again without any cololing, it will place a large strain on your system. You're an engineer, try to visualise it by drawing a picture or something, and it will be quite clear once the penny drops :thumb:

Thanks Tony :thumb:

Looks like I have to add a thermo to my onroad spares kit.

The comment about Toyota's design is just a general engineering principle. Where possible, you anticipate the failure of certain components, and design the system so that it will still work. But it's not always possible or practical.

[Byrnesy]

You will find that some of the Toyota thermaostats are adjustable. They hanev a set screw and lock nut on them. I had overheating, not boiling, problems on a 2H.

That was after new radiator, new water p/p, block chem clean and genuine toyota clean.

I installed thermocouples in front and behind the radiator to see air temperature increase. I.E. the amount of cooling achieved.

I then was put onto the fact that you could adjust the thermostatat so pulled it out and put it in a pot of water and brought it to the boil. I then measured the amount it opened. Cant remember the figures of the top of my head but a made a adjustment then repeated the process and it opened around 20% further. Then re-installed it and never had another problem.