Chev 6.2/6.5L Diesel Engine Tips and Tricks

[Les Addison]

Left is a standard RH rotation pump showing the White arrows Diam at 98mm. the red flow gap 7mm is too small. The std impeller has 8 vanes.
Next one has been modified White Diam is 115mm. Yellow has been machined down to top of seal depth and diam increased to widen the flow gap to 18mm. The impeller for this pump has 3 vanes, and pumps nearly three quarters as much more volume and pressure, than std.
Third one is a High Output 110LT/ min genuine GM pump for 6.5 & 6.2 reverse rotation Serpentine belt drive.
As for air flow under the bonnet I tried everything known to man, including removing the bonnet . It simply does not alter the engine temperature.My orriginal 6.2 with a 5 staggered core and an Isuzu large bottom tank, in snow country hills would over heat. The air scoop I built ,directs air up to the bottom of the radiator changed it to the extent the fan cuts in about half the amount of times. The radiator is biggest single thing to control heat, with water flow and pressure next. The other thing that the 3 cores do is to allow the air to circulate around them better, and the extra row per inch supplies another 3 extra cores.
The best one I have found is where I described it earlier on, 3 rows 16mm x 2mm 4 rows per inch and more fins. The Nat Rad core can be fitted to any 4wd. Check your water pressure , this modified one pumps 30lbs and up, easily at about 2500 revs with the thermostat closed.It cruises at 18lbs at 2000 revs (at 100kph, Turbo 700 R4 locked up ) at normal opperating temp 85C.. Brunswick Diesel dont use modified pumps as the cost is added to the install, they use the double thermostat housing, which increases the flow but not the pressure. Check your EGTemp , for over fueling.. Les

[Les Addison]

It is imperative to fit push rods the right way up. Note the bronze or grey colour on the bottom half of the ball in left pic, this ball is very hard to resist the galling action of the rocker arm, and goes to the top.
Next pic the bottom end is softer to allow it to bed into the cam follower, as oil is pumped up the rod to the overhead gear.1982 /3 models had full shiny balls top and bottom,could be used either end up as the rockers were cast iron. When repairing these models always replace the push rods and overhead gear with the pressed steel type.
Grease the rockers, and work the grease around . Replace the teflon buttons if they are brown in colour as they are old or over heated. They are white when new.
Inspect the sockets ,if the wear is above the oil holes, the oil will not get to the moving parts. Slight wear on the stem contact face can be buffed off. Grease bottom of push rods. Tighten rocker shafts evenly to prevent breaking shaft or support posts.

[Les Addison]

Ten bladed Falcon EA to ED fan &heavy duty viscous coupling.
Left handed thread , adapter with the 8 Chev water pump flange bolt holes.
This fan works very well and can be easily heard when it locks up. It is easy to remove by simply using a large open end spanner

[bilbo]

Les,

I've got a 6.5 in a Nissan Patrol, fitted by Brunswicks about this time last year. I find your "tech tips" excellent stuff.

However, I can't see the pictures and they would be handy. Anyone got any ideas why the pics don't work?

Thanks,

Bilbo

[Les Addison]

Sorry Bilbo , I have figured out how to place the pics into links . Shal fix them all.. Les

[6.5Cruzer]

Les I am very interested in what you have had to say about over heating of a 6.5. I have one in a 75 series that I have had alot of problems with keeping it cool. At the moment I have got it so you can drive it at 100kmph but as soon as you put it under any load up goes that gauge. Currently I have a 1/2' restritor in the tophose. (I know you said that it doesn't work) I have the hose's running from the back of the heads to the water manifold and I have also converted the radiator into a triple pass. It has the rad that Brunswick recomended the 9488. I have had 2 fan clutches it has 1HZ thermo stat the motor has been out and apart and every thing crack tested all ok. Brunswick then sent over another long motor and I installed that. Now it runs ALOT cooler than the first engine so there must have been something wrong with that engine. But it still seems to run hotter than I would like. Now I have put the over heating of 6.5s down to 2 things. Not a big enough cooling system and no where near enough engine oil in it. I am currently in New Zealand working and there is fella in the yard next to us that has a GMC with 6.5 Turbo in it. I asked him if I could have a look at it. Now the radiator core in it was 850 wide by 450 high and 45 thick (BIG). I asked this guy what it is like and if it get's hot. And his answer was "you can only drive the heap of S$#t in winter". Now that has alot bigger cooling system than a Toyota or nissan. That solves problem 1. The second problem I believe these have is the isn't enough engine oil in them. I have alway believed that engine oil is as much of a coolant as the cooling system it self and that eng oil temp should be very close to cooltant temp. Now my engine has less than 7 litre of oil in the hole system including filter and cooler. After you take it for a easy drive and stop and measure the oil temp (On side of sump) with laser surface temp gauge it can be any where up to high 90 deg c. That's way to hot for eng oil. I installed a oil cooler about twice the size as the original and hey presto engine runs alot cooler. An engine that size should have well over 10litres of oil in it. A 1HZ has i believe 12 litres in it and its only a 4.2 litre so a 6.5 should have alot more than 7. So I am currently in the process of making a real big sump for mine, want to get at least 12 litres in it I have also got PWR up in the gold caost to make me second radiator which I am going to mount up on the headache rack. Not the most ideal fix but if it mean I can work it hard on a hot day I'll do it.

Reg

Craig

[Humvee]

Hi Les

Most interesting read, and imformative posts

I have a 96 Hummer, It only used to run hot in the sand after an hour or two of hard work, some of the guys i know with turbos say theres run hotter, even coming up the moony moony bridge on the way to sydney (i know your in brisbane), anyway, we have cooling probs as you know in the 7th - 8th cyclinders, I have just had a head gasket replaced, and brought a High flow water pump kit from Kennedy Diesel in the US, The pump alone states it increases flow by 70% and a further 9% in through the radiator, I then had it further modified by Ecotrans, and some other Mods Ecotrans recomended to increase flow around the block, they machined custom welsh plugs with deflector to push the water up the back of the block, and re machined the water pump, We also installed the cooling loop all the yanks talk about on humvee.net, It doesnt run hot at all now, John Bennett knows whats he's doing, and has done a few mods to Hummers, and chev motors, i would recomend him to anyone..

Like ozhumvee says the water wetter also drops the temp significantly..

Just a question with the injector pump, from your experience do you recomend dailing up the pump? I have a Stevodiv DB2831-5088 pump, Gemini Diesel says to dail it into 8?? This doesnt mean much to me, im still learning, they say the turbos are dailed to 12, what is the standard non modified pump dailed too? and how much of an increase would it make being dailed to 8, where would i notice it, apart from probably drinking more fuel?? Right now i get 16L/100kms sitting at about 105kph on the freeway, i can do more, but im in no rush.

Thanks in advance..

[adamkenn]

Hi les having trouble with my chevy diesel 60 series as well you sound very knowledgable on the subject mine only overheats on the highway, fine around town and idling etc. Have a new 80 series fan and clutch with new std 60 series diesel radiator any help would be fantastic. Also what it the sender in the back of the valley used for ?
Regards Adam

[Peter Aawen]

6.5Cruzer, you say you've put a larger oil cooler on your machine but you are still looking at making a larger sump to aid the cooling; wouldn't it be a better thought to add a seperate oil reservoir after the oil cooler that would allow your increase in oil capacity without stuffing around with the carefully designed internals of the sump? If your fabricated sump doesn't have the same oil level (not necessarily same depth, make it as deep as you like but it'll stuff up your departure angles and possibly impede the front axle/steering) or splash characteristics you could end up with some fairly drastic lack of oil problems.

[Les Addison]

In answer to a question from Humvee

Some GM vehicles and early Hummers used Th400 auto gearboxes, They require a vacuum valve to supply a signal to up shift gears, and a switchable 12volts to the kick down. valve assembly from injector pump. Apply vacuum to bottom port, and vac gauge to top port, rotate the spring loaded throttle switch At idle should be max vacuum. At wide open throttle (WOT)should drop to about minimum to zero.If not screw the knob up or down to adjust. Test the micro switch ,place an ohms meter across the two wires , rotate the spring loaded throttle switch, and note the micro switch making contact. After adjustment, refit the valve with the bolts in the center of the slots ,attach the bottom port to the gearbox vacuum modulator pot. Attach the top port to the vac pump source.Reconnect the 12v wire to the switch on the left side of gear box. Drive vehicle , and move valve on slots to obtain correct up shifting. Finer adjustments can be achived by screwing the knob.

[ozhumvee]

Just a bit of info on the trans in Humvee's Les.
They ran a TH400 until about 94 or 5 then changed over to a 4L80E.
The turbo 400 has a mechanical modulator and an electrical (24v) kickdown.
The modulator is linked to the throttle linkage by a cable. The kickdown is operated off a microswitch on the side of the injection pump.
There is no vacuum on a humvee, brakes etc are hydraulically assisted by a hydroboost running off the power steering system.
My Humvee is now fitted with a 4L80E controlled by a Compushift controller ([url]http://www.compushift.com)[/url], it made a huge difference to the truck, reduces engine revs by 850 rpm at 95kph, cooling fan cuts in far less, far less heat and noise as well.
Re the post on the oil capacity it could be a point in the heat problem as the humvee runs around 8.5 litres of oil but it has an oil cooler approx 500mm wide and 300 mm deep which combined with the huge radiator, cooling system capacity of 26 litres and a 12 bladed fan which is either on or off (no thermo fan but a direct clutch operated by hydraulic pressure from the power steering circuit and a temp sensor) it has NO overheating problems ever. In fact with the 4 speed and its lockup torque converter the engine actually runs cooler than ever on the open road.

[Flywest]

I would think lack of oil cooling is a distinct possibility in a 6.2 or 6.5.
As stated the 4.2 Cruiser diesel runs 12 litres of sump oil and the 7.3 PSD runs 16 litres!

Those of us with bypass oil filtering add another litre for the cannister & lines!
The 7.3 of course runs an engine oil cooler!
Mine runs 7 radiators in total now:-

1. Engine water Radiator
2. Intercooler Radiator
3. Power Steering Fluid Cooler
4. Air Conditioner Radiator
5. Std Transmission Oil Cooler
6. Aux Transmission Oil Cooler
7. Engine Oil cooler.

I also run a alloy deep pan sump on the E40D 4R100 auto transmission, which holds an additional 3 quarts of trans fluid and has build in air cooling fins.

To give some idea of what Les is talking about with his EGT's, he is spot on...

I can hold Trans temp to less than 70C on uphill haul with 9000lbs of boat on behind, 15 psi turbo Boost and EGT of 550C...



This is on a day when the ambient air temp was 46C (114.8f) hauling over the mountain range up the nor west cape headed into Exmouth into a 40 knot breeze!

How do I keep the temps down?

Water sprays out front plumbed from these two tanks holding 200 litres between them!!


I use a 12V marine deckwash pump, and it's switched on the dash so I can activate it anytime the EGT's and trans temp start to climb. The water is plumbed to a couple garden misters behind the grill!

You can notice the temps drop as the misters come into play - the EGT's go down, the air con blows cooler, the trans temp stays below 70C

Amazing what a bit of evaporating water on those radiator cores can do (Same principle qas the coolgardie safe really!).

Lastly - don't underestimate what Les is saying about the coolant and use of a surfactant to stop cavitation. If you've ever seen the pitting that cavitation can cause to a stainless steel prop on a boat it isn't hard to imagine it eating its way thru cast iron block!

When those superheated steam bubbles caused by extreme low pressure collapse - they effectively hammer the outside of the cylinders walls in the water jacket!

Now you mightn't think that would damage anything - but - you know, hammering the metal was a method the Germans used to form rifling inside rifle barrels - they would heat the rifle tube up sufficiently to fit it over a barrel twist mandrel, then as it cooled they would hammer the outside until the inside toook the shape of the hardened mandrell...resulting in a rifled barrel.

Some German manufactured rifles are still made this way (Anschutz for ex)..

Well the superheated steam bubbles when they collapse - the resultant hammering effect of the water is like a million small men inside the water jacket htting the outside cylinder walls with ball pein hammers!

You have to know thats going to eventually pit it's way thru or deform the cyclinder walls inside the bore, just like the German rifle making practice does!

Get the right surfactant coolant and change it out at LEAST every 2nd year!

Interesting thread.

Cheers!

[Les Addison]

In answer to Nev 62s question re. tapping noises..
This noise can come from a few sources,such as, broken valve spring, faulty hydraulic lifter, loose rocker shaft, loose or broken piston pin circlip, dribbling injector nozzle causing detonation, cracked piston skirt, and a rare one , broken injector needle spring, this will cause minor to servere detonation knock. Another problem is caused by the tip fo a glow plug burning off and imbedding into the top of a piston,striking the cylinder head.. As to the poor perforfmance problem Nev. Have your compression tested , 350 to 400 will result in poor cold starting. Should be 480 to 500psi hot. Test injectors 1750 1950 psi. Fuel pressure at pump 5 to 9psi. After the last filter 3 to 7 psi.... 0 to 1psi from injector pump to tank return line.....As the injector pump is reliant on these pressures, it will impede it's performance. There is a transfer pump built into the injector pump that will keep the engine opperating if the lift pump fails, but with a noticeable lack of power . After all fuel pressure tests are ok , fit a clear 1/4"hose to the fitting on top of the pump (return line),run engine at 1500 to 2000 rpm and check for air bubbles. To locate source of air bubbles , use suitable size clear hoses , to test all joints from tank to last filter. Can also come from internal seal leak in pump. Air can be sucked into the rolled edges of throw away fuel filters, even if no fuel leak is noticeable. If all checks out ok, the calibration of the pump is paramount on these engines to get full performance.. Les

[Nev62]

In answer to Nev 62s question re. tapping noises..
This noise can come from a few sources,such as, broken valve spring, faulty hydraulic lifter, loose rocker shaft, loose or broken piston pin circlip, dribbling injector nozzle causing detonation, cracked piston skirt, and a rare one , broken injector needle spring. As to the poor perforfmance problem Nev. Have your compression tested , 480 to 500psi hot. Test injectors 1750 1950 psi. Fuel pressure at pump 5 to 9psi. After the last filter 3 to 7 psi.... 0 to 1psi from injector pump to tank return line.....As the injector pump is reliant on these pressures, it will impede it's performance. There is a transfer pump built into the injector pump that will keep the engine opperating if the lift pump fails, but with a noticeable lack of power . After all fuel pressure tests are ok , fit a clear 1/4"hose to the fitting on top of the pump (return line),run engine at 1500 to 2000 rpm and check for air bubbles. To locate source of air bubbles , use suitable size clear hoses , to test all joints from tank to last filter. Can also come from internal seal leak in pump. If all checks out ok, the calibration of the pump is paramount on these engines to get full performance.. Les

Thanks for that Les, guess it is time to start pulling the inlet manifold off so I can get the rocker covers off

[Rock ape]

To Les Addison,
Thank you for passing your knowledge of these engines.
I believe you are retired and I take my hat of to you. You have helped a lot of people with your knowledge that you didn't have to.

I have one in my troopcarrier, I haven't had to ask you a question but I enjoy your info. Thanks for shareing the years of knowledge you have gained
The Rockape