90 Brake Problem - stumped

Hi,
wonder if anybody can help please.
Have replaced master cylinder seals, calipers, rear slave cylinders and flexible hoses.
Brakes seem to bleed properly (clear fluid, pedal goes hard etc).
Go for a test drive and after a few presses the pedal seems to go spongy also although all the brakes are working, the rears seem to be locking up when pressed hard.
Get back to the garage and there is no fluid loss, the adjustment is still seemingly o.k. - I'm stumped.
There is something that is supposed to limit the pressure to the rear wheels but no idea how to check it or if it could cause the symptoms I'm descibing.
Any ideas please?
Cheers, Mick

Hi Mick

There is indeed a compensator that sits between the axle and the chassis. Its job is to increase the amount of fluid passed to the rear axle when there is an increased load in the rear.

I have seen loads of these seized!

Try this as your first stop!

Your spongyness might be being caused by a good servo giving you that impression. Let me know how you get on.

Jim

Jim,
thanks for the reply. Still no joy I'm afraid. The pressure limiting device on mine is under the bonnet and has no means of sensing the vehicle load. Have now replace all the hydraulic componentsa and the system seems to bleed o.k. but when the engine ois running, the brake pedal slowly sinks under the foot. There is not a drop of fluid on the garage floor. Can't understand it, not sure what else to try.
Cheers,
Mick

Mick Aberdeen said:

when the engine ois running, the brake pedal slowly sinks under the foot. Mick

Click to expand...

Thats pretty normal Mick.

as long as it pumps up ok when the engine is not running!

ta

Jim

Hi Mick,

I know you have changed/serviced the master cylinder, but it sounds like master cylinder problems. Did you just change the rubbers in both the systems?

Frosticles

Me again!

Have the rubbers gone back in the cylinder without folding? Are the chambers clean and not pitted?

Frosticles

Hi folks,
happened to be in the local Fiat dealer at the weekend and asked the head mechanic if he minded having a look (turns out he's a landy fan) and he too reckoned it was normal. (Am now taking it there for an MOT next week in the hope he doesn't change his mind).
Just as a side issue, went over the highlands to Aviemore on sunday to pick up a roofrack (a full length galvy box section one with a ladder up the back) forgot to measure it and it now doesn't fit in the works car park! On the plus side though, there's a nice dusting of snow over the higher peaks - very pretty drive back to Aberdeen.
Cheers,
Mick