spongy brakes

[ScottieJ]

did you bleed the brake bias valve thing on the inside of the drivers side chassis rail near the fuel filter? some have a bleed nipple others don't.

[Darrell]

Spongy brakes is normally because of air in the system and often the bias valve is overlooked as Scottie says. If the pedal has more travel than it should before the pedal has good resistance this is most likely the pistons in the cylinders travelling too much due to the self adjusters not working. As you know these are knackered it's best to sort them and see how it feels before messing with anything else.

[samurai gary]

ok thanks, i am trying to find some adjusters, also would a faulty servo cause the spongy brakes.....

[Anton]

I suppose, in theory, yes it could - if it was letting in air or otherwise leaking. It wouldn't necessarily let brake fluid out if it's letting air in, but it's likely (considering the pressures involved).

The fact that it was ok before you replaced the rear cylinders suggests it's not the problem. Suggests, not proves, but suggests very, very strongly.

Unless you played with it somehow during the swapping of the brake cylinders?

[samurai gary]

when i first bought the anus the brakes were siezed and the vacuum pipe on the servo was blocked, could this have caused damage to the servo without me realising as the braking system was in a bad way.

[ScottieJ]

The servo shouldn't effect the pedal apart from making it lighter. If the seals have gone in the master cylinder it could cause spongy brakes. These guys should have rebuild kits for the master cylinder http://www.brakesint.co.uk/

[Anton]

It "could" have caused damage, but I'd have thought that more than likely not, since you said that your brakes worked ok for a while (presumably *after* the blockage was cleared?). The blockage would simply have stopped it working properly (or at all) until it was sorted out - it's almost impossible for the blockage to have moved from the pipe into the servo because the pressure of the vacuum line would have made whatever was blocking it want to go the other way - into your engine's intake manifold.

Having said that, how do you get a blockage in the vacuum pipe of the servo? I can only think that it was kinked, or something in the servo came loose - perhaps a piece of a seal/gasket or something. If the problem was a kink, I'd think you're fine - if not, it might be worth stripping down the servo and replacing the gaskets, just in case.

But again, having said that, I can't see how a faulty servo would make the brakes spongy. If anything, a faulty servo would make the brakes too hard!

[samurai gary]

i agree, i feel if the servo was faulty it would make the pedal hard, i have a hissing sound when i push brake pedal. not sure if this is normal... i may try an overhaul of master cylinder, ....

[Anton]

Where's the hissing sound coming from? Do you get the hissing sound when the engine is running and you press the brake, or is it also there when you press the brake pedal without the engine running?

And has this just started, or was it there when you took the car to your mechanic?

[twiss]

Hissing sounds probably mean master cylinder seals have gone!!! :(

Get a mate to press the brakes on and off with the engine running and listen to the master cylinder.