Spongy brake pedal on HZJ75 UTE

[Tinman]

Brakes have not been good for a while. So this is where I am at.
Front discs and rear drums.
New rotors on front with new bendix pads
New drums on rear with new bendix shoes
No fluid leaks and have run 2 bottles of brake fluid through to bleed the air and flush out any old fluid.
The hand brake is good. 3 clicks

The brake peddle is still spongy and bleeds down.almost to the floor.

Any thoughts or experiences with this would be appreciated.

My thoughts maybe two possibilities.
1. is there any valve in the master cylinder that could cause this?

2. There is a load proportioning valve in the brake lines on the rear axle. Could this be causing the problem.

 

[Clint79]

yep
as hulsty told me
check the front wheel bearings as strange as it sounds that was the prob with my spongy pedal that would sink to the floor

 

[Tinman]

yep
as hulsty told me
check the front wheel bearings as strange as it sounds that was the prob with my spongy pedal that would sink to the floor

Bearings are good. Just done them. That should only affect it when in motion due to the movement on the calipers, but this does it just sitting there.

 

[Aussie 25]

Have you ajusted the rear brakes right up and blead the bleader on the load valve ?

 

[Tinman]

Rear brakes are adjusted up and have blead the load propotioning valve.

 

[Aussie 25]

How old is the master cyldner. Sounds like that if you have changed all the rest. Just loosen it off the buster and see if aney fluid runs out. that is usley a good sine they are hadit. No more than $100 for a complet new one.

 

[Cruiser70]

Brakes have not been good for a while. So this is where I am at.
Front discs and rear drums.
New rotors on front with new bendix pads
New drums on rear with new bendix shoes
No fluid leaks and have run 2 bottles of brake fluid through to bleed the air and flush out any old fluid.
The hand brake is good. 3 clicks

The brake peddle is still spongy and bleeds down.almost to the floor.

Any thoughts or experiences with this would be appreciated.

My thoughts maybe two possibilities.
1. is there any valve in the master cylinder that could cause this?

2. There is a load proportioning valve in the brake lines on the rear axle. Could this be causing the problem.

My mates been through hell and back with brakes on an LJ70(disks front, drums rear), its been going on since he owned it.
The LSPV was the cause after replacing all pipes, brakes, calipers, disks, we had even replaced the LSPV with same results.
Dont worry about that stupid adjuster that attaches to the diff.
Go staight for the source, the LSPV body, undo the two bolts and it slides up and down, slide it all the way up, drive around the block. better? slide it down , drive around the block, better?
Cannot remeber which way it should slide, try it and see certainly worth a go. of course do the obvious first, bleed brakes etc...

Let us know how it goes.

Martin.

 

[Clint79]

LSPV =?

 

[Aussie 25]

LSPV The load valve above the rear diff. If you relay think it is the load valve, bypass it and try, easy. Take the top steel line out of the frount of the valve, conect it up to the rear hose. Follow the steel lines to the frount. Where the jounchion is remove the bottom one and plug THE JUNCHION up. Re bleed brakes. If that dont fix the spunge change master cylnder TEST DRIVE and reconect LSPV.

 

[SimonInAustralia]

LSPV =?

Load Sensing Proportional Valve

Varies the amount of brake fluid pressure/torque at the rear brakes.

Stops rear wheels locking up with a light load, gives enough braking force at the rear wheels when loaded up.

After fitting a suspension lift it might be put out of adjustment, as the sensor thinks the load is lighter since the chassis/body is higher, and and it allows less pressure to the rear brakes.

 

[GregFrench]

I am having the same problem, but I can't find anything that resembles what you describe. Got pics?

 

[Aussie 25]

Hi Greg ,What car do you have?

 

[bigbrowndog]

It really sounds to me like you have air in the front section of your master cylinder. Unscrew the brake line and pump some fluid through and watch as it is pumped steadily. Then reconnect it an open the furthermost back wheel and bleed all air out of this line.
Bleed the LSPvalve then other back wheel. Then the front wheel furthermost from the master cylinder then the closest.
The load sensing proportioning valve is bolted to the inside of the chassie rail above the axle and has a spring rod running from it to the opposite side of the back diff pumpkin.

 

[Clint79]

Load Sensing Proportional Valve

Varies the amount of brake fluid pressure/torque at the rear brakes.

Stops rear wheels locking up with a light load, gives enough braking force at the rear wheels when loaded up.

After fitting a suspension lift it might be put out of adjustment, as the sensor thinks the load is lighter since the chassis/body is higher, and and it allows less pressure to the rear brakes.

cheers mate
LSPV Load Sensing Proportional Valve i see , i allways just thought PV
the LS tricked me lol

 

[Tinman]

Hade a bit of a play again today.

Played with the LSPV and adjusted it abit. My rear springs are a bit sagged so I ajusted it down on the diff end which should compensate for that. Also while I was there operated the valve a few times up and down. Took it for a test drive and wow. The rear brakes worked or at least one did. So I checked that the other (LH side rear)was adjusted up properly that was good so blead it again. Had a bit of crappy fluid come through so I obviousle had not pumped enough clean fluid through that line. So took it out for another test. Both worked much better. and I was able to get both rears to lock up.

The peddle now is much better. It doesnot fade down now when I hold pressure on it. I am still not 100% happy with the way the peddle feels but the brakes are working better than I can ever remember.

Thanks for the imput from all.