brake probs need help ('91 Hilux)

[lux2.8]

alright i own a 91 hilux its a diesel
pretty much the brakes are not working all that well they will not lock and when im on them hard they get to a point and wont brake any more things that i have done new pads new rear drums new brake master cylinder check valve working good vacume is perfect as i tested it against another hilux with a gauge now what could it be the brake booster when i depress the pedal several times when the car is off then start it with the pedal on there is a movment down, or could it be glazed rotors ive heard of this affecting braking performance but they got lots of meat on them any help with this would be great as its an accident waiting to happen
cheers jason

[torque steer]

The brake booster is meant to drop a bit when the engine is running.
what were the brakes diong prior to the work you've done and are they now any different.
Have you a decent pedal height?
Are the wheel cylinders working(could be seized)?
Caliper pistons not jammed after the new pads being put in.

[Peter @ Aawen4x4]

If you've got oversize wheels on the vehicle, and you haven't done anything to upgrade the brakes, then that will be the most likely reason you don't have good brakes!! Anything over about 30" on an earlier Hilux is pushing it, and the later units don't do very well over 32" anyhow, so how big are your wheels??

[FourXfouR]

My Hilux will lock up my 32" muds without a drama so I doubt tyres are your problem. Have you checked the hoses between the alternator vacuum pump, vacuum tank and booster. They can either become soft and pinch together or brittle and leak. Worth a check

[TazMAV]

alright i own a 91 hilux its a diesel
pretty much the brakes are not working all that well they will not lock and when im on them hard they get to a point and wont brake any more things that i have done new pads new rear drums new brake master cylinder check valve working good vacume is perfect as i tested it against another hilux with a gauge now what could it be the brake booster when i depress the pedal several times when the car is off then start it with the pedal on there is a movment down, or could it be glazed rotors ive heard of this affecting braking performance but they got lots of meat on them any help with this would be great as its an accident waiting to happen
cheers jason
The pedal will drop as you described when it's working properly(booster that is). Have you completly bled the system as it's sounds like that may be the problem, make sure you start at the rear passenger side and work forward from there finishing at drivers front. Try that and if thats not it seek expert help.

[lux2.8]

thanks for the replys guys first off wheels are 31 muddies but i had this problem back when i had smaller wheels dont think caliper pistons are seized because the old pads were evenly worn, the brake system was bled twice so thats not it, vacume is good and the lines are good the only thing i didnt check is the wheel cylinders how would i go about checking these? also the lspv would that play a part in the back brake performance at all??

[Hj45er]

thanks for the replys guys first off wheels are 31 muddies but i had this problem back when i had smaller wheels dont think caliper pistons are seized because the old pads were evenly worn, the brake system was bled twice so thats not it, vacume is good and the lines are good the only thing i didnt check is the wheel cylinders how would i go about checking these? also the lspv would that play a part in the back brake performance at all??

another point have your rear wheel cylinders been adjusted properly if not your back breaks wont be working

[wado]

yes check the adjustment of you back breaks if they are not adjusted right then your peddle will go to the floor with stuff all breaking power.

[HDJ105]

also the lspv would that play a part in the back brake performance at all??

Of course, the LSPV adjusts rear brake pressure dependant on rear axle load, sensed using the suspension height.

If you have lifted the suspension your LSPV will think you no load and apply minimal pressure ot the rear brakes to prevent lockup.

[Hj45er]

Of course, the LSPV adjusts rear brake pressure dependant on rear axle load, sensed using the suspension height.

If you have lifted the suspension your LSPV will think you no load and apply minimal pressure ot the rear brakes to prevent lockup.

hey hd just a question how does lspv work im guessing its some sort of computer sensory thinga mi jig :computer: im old style 40 series level:)

[HDJ105]

hey hd just a question how does lspv work im guessing its some sort of computer sensory thinga mi jig :computer: im old style 40 series level:)

LSPV = load sensing proportioning valve.

It's a mechanical valve connected to the brake system, usually located on the chassis above the rear axle, with an arm fixed to the differential to sense the load on the rear axle, and proportion the brake pressure according to that load.

I reckon the 45 will have one, even non ABS equipped 100 series still do ;)

[Hj45er]

LSPV = load sensing proportioning valve.

It's a mechanical valve connected to the brake system, usually located on the chassis above the rear axle, with an arm fixed to the differential to sense the load on the rear axle, and proportion the brake pressure according to that load.

I reckon the 45 will have one, even non ABS equipped 100 series still do ;)

Oh i see :o , my brake line passes over the rear axle where it passes through the diff breather but there is no mechenical arm or anything but still could be a valve or something i might have to have a look sometime thanks hd

[lux2.8]

how do i go about adjusting the lspv and wheel cylinders then because its up on chassis stands due to a snapped cv shaft cheers

[HDJ105]

how do i go about adjusting the lspv and wheel cylinders then because its up on chassis stands due to a snapped cv shaft cheers

Have you lifted your truck? Does it run larger tyres than std?

Usually the manual will give you a measurement for the length of the rod, and if you lift the vehicle you should extend the rod by roughtly the same amount.

However, if you have larger tyres and / or carry more weight than std, start by adjusting the rod to resemble a fully load, then carefully go for a drive on an isolated wet or dirt road and do some test stops.

If the rear wheels lock before the fronts back the adjustment off and try again.

Of course we are talking about brakes here, so if you don't feel comfortable playing with them consult an expert!

[lux2.8]

well the hubs are off had a real good look at left hand side caliper turns out 3 pistons are seized they were not like that when did pad change 6 months ago tho so i called up the local wreckers $110 per caliper and 6 months warranty or $180 per caliper for the brake guys to fiddle around with what shall i do

[FourXfouR]

Is that price for a rebuilt caliper? If not you should be able to get exchange items for about that

[lux2.8]

nah they reckon that they will take the caliper apart and replace the seized pistons kinda leaning towards the wreckers

[FourXfouR]

I suggest calling a brake mob and just asking what an exchange pair are worth. Generally cost you less because you are giving them your old caliper to rebuild and sell to the next person

Also that way you avoid any potential issues with your current calipers. Sometimes the bores can be scored or pitted and cannot be rebuilt.

[beast2h]

Oh i see :o , my brake line passes over the rear axle where it passes through the diff breather but there is no mechenical arm or anything but still could be a valve or something i might have to have a look sometime thanks hd

my old mans 47series had one. The valve was directly above the rear diff on the right hand inner side of the chassis rail! the sensing rod come out of the valve and looped over to the diff housing on the left hand side! if that helps

[d3m0n1c_4b]

if you have a lift kit, did you raise the load-sensing valve?? i personally havent had this prob on mine(i dont think, brakes dont seem too bad) but i have heard that if you lift your fourby and dont raise the base of the load-sensing it basically acts as if there is no load and therefore reduces braking force in the rear.

[lux2.8]

well all figured out then thanks for your replys the new calipers are on with new bendix pads and im gonna tinker with the lspv i think shes gonna pull up hard now.

[luxa]

Which calipers did you end up with, and what $ ?

Cheers

Luxa

[lux2.8]

um ended up with a pair of calipers from the wreckers for $150 and 6 months warranty just got bit lucky they seem pretty smooth to thanks all

[Dippy]

Did this fix your problem?, I have exactly the same problem with my '93 sr5 and I have just put in reconditioned callipers but still have the same problem.

[lux2.8]

yeah the problem is now fixed it was seized pistons new ones are in with some bendix pads now i can stop its great

[Hj45er]

Good to hear all is well :p

[lux2.8]

problems again went throught a biy of mud and water the other day after that it was all over brakes were shit again and the pedal went hard again pulled them out gave a good clean ruffed up the pads and rotors with some sand paper they work better but not as good as when i first put them on can mud and fresh water **** them ??

[FourXfouR]

You will find it probably glazed them up, give them a rough up and bed them in with some heavy stops

[lux2.8]

well i tried that umm no pistons seized cleaned rotorsw and pad hit them with a bit of sand paper heres what happens comes to a slow stop first time you hit the brakes now when you get some heat into them you can feel them go on a second or two later they will bite its also a pretty hard pedal feel. i was wondeing could pitted or scored pistons do this or should i be looking at pads and rotors??

[lux2.8]

need some help with this one now guys heres whats going on with it went through some mud and water i now have a very hard pedal feel and the brakes wont lock at all they dont work that well so i did what was suggested ruffed the pads and rotors up and tried to bed them no change, now a guy told me the bendix pads were to hard a compound so i changed over to a soft set still nothing so i have put it down to the rotors or calipers the calipers pistons are not seized the rotors have a bit of meat on them but are very shiny should i go out and get a set of slotted rotors or what im sure someone knows whats going on so please help

[FourXfouR]

How deep of a mud hole was it? Is the pedal hard all the time?

[lux2.8]

it was a pretty good one bit to much fun yeah it has the same kind of pedal feel as seized pistons but there not yeah it is hard all the time i find when i got some heat through them they worked a bit better i know the pedal is meant to drop down further than this as well because before this it had a great pedal feel to it and the backs would lock as well as the front, now the backs dont lock up aswell. any suggestions

[FourXfouR]

Have you had a look at the back brakes? You may find you have a heap of crud within the drum. It could also be stuffed wheel cylinders. Was the mud deep enough to reach the alternator? Be sure to check over all vacuum lines again just to be sure there was no leaks etc

Mud is fun but can cause alot of problems, especially when your missus has a go at you for washing the truck on the driveway haha...my bad!

[tony61]

Sounds a bit vacum related expensive little units to those pumps.
slightly off topic the brake bloke here in kalgoorlie did a mod on my mates lux fitting up landcruiser calipers and rotors that made a heap of differance to stopping with larger tyres.

[lux2.8]

nah the alternators fine that was the first thing i checked vacum pumps all good to im pretty sure the rear brakes are fine thinking i might just drop it to a brake mob cant be bothered any more thanks for the help

[FourXfouR]

Yeah I think it has come to that mate, not really something that can be diagnosed over the internet by the sounds of it. Good luck with it mate and be sure to let us know what they find