GQ Brake problem

[chadd1981]

Hey guys,
Just wondering if you would be able to help me out a little as i am still having problems with my brakes in the Patrol. Okay what i have done so far:
Master cylinder replaced
Brake booster checked, all okay
rear load sensing valve (replaced with second hand valve)
new rotors on rear with new pads
Full system pressure bleed.
Bearing checked, all okay
I am still having problems with a spongy pedal. If i jump on the brakes, it struggles to pull up.
Any ideas would help.
Cheers

[ozy1]

well if your avtar is anything to go buy, you have some lift, when you fitted longer brake lines did you use rubber or braided lines?

if rubber could they be expanding under presure, as i believe this will give the effects your talking about,

just another avenue to check,

[chadd1981]

Thanks mate, but they are braided lines.

[ozy1]

what about the lines from the diff to the caliper, the short factory rubber line,

i had one last year with a very minor leak, as in the hose was damp and gave me thesame problem

[AJS]

Have you checked the small vacuum line that controls the idle speed for the air-con, the one that runs from the alternator back along the firewall? If there's a leak in that, or if the line has come off the pump outlet, you'll run out of vacuum very quickly. Also check the one way valve between the pump and tank is working correctly. HTH.

[Cossie]

excessively worn front rotors?

[oozuk]

i know this might sound silly but are you bleeding you brakes correctly ?

Have you tried using a vacumme bleeder ?

[chadd1981]

thanks for the comments guys.

The front rotors are fine

Yes they are being bleed the correct way.

It seems like there is air in the system some where but we just cant find how the air is getting in there. The Master Cylinder has been replaced with a brand new one and there is no leaks anywhere.

[purplebus]

mine did exactly this and we changed everything.check along the brake lines towards the rear of truck to see if there is a weird cylinder setup in the brake lines on the chassis. i had the same prob and we found this object and removed it as it traps the air. apparently was on the mq super deluxe and on some early gq's. the mechanic had never seen it before on a gq? good luck

[meiamaro]

If you clamp both brake lines to the front and rear diffs
and press pedal, hard pedal.Master is fine.
remove rear clamp, hard pedal, rear is fine.
spongy pedal,its in the rear.
repeat same steps on front.
then you can do each caliper.
this will help point to the problem area.

Cheers Ian.

[JBE]

I am very interested in this post as I have a similar problem. Funnily enough, I have a 93 TD42 LWB as well. I bled the breaks multiple times, got a workshop to bleed them with no success. I also swapped the proportioning valve, replaced the rubber hoses at the calipers with new ones and used braided lines from chassis to the diffs. Nothing made a difference. The master cylinder seems to be fine as the pedal does not sink.
I’m starting to believe that the problem has to do with the vacuum system, but I can’t find anything obvious.

Cheers
Joachim