94 1.2 braking problem - Bluesky
I'm currently repairing a 1994 Vauxhall Corsa which has the following problem:

When the engine is running and the brake pedal is pressed and then released it stays down for a few seconds and the brakes remain on. If the engine is not running the pedal returns immediately although the travel is less. Also, after the engine is switched off the servo can be heard 'hissing' for approx 15 seconds after which it stops and pressing the brake pedal proves that the servo has lost vacuum. Finally, I have noticed that if the brake pedal is pumped several times with the engine off a 'bubbling' noise can be heard coming from the hydraulics. Note that the pedal is not spongy.

Does anybody have any idea whether the problem is in the master cylinder or the servo.

Any help would be appreciated.

Edited by Pugugly on 30/03/2009 at 21:43

94 1.2 braking problem - Number_Cruncher
You definitely need a servo, and you most likely also need a new master cylinder. If you find the servo is half full of brake fluid when you take it apart, you definitely need the master cylinder.

94 1.2 braking problem - Bluesky
Carried out further checks. Removed master cyinder from servo to see if master cylinder was leaking. It appeared to be dry but also has a new appearance as do the two hydraulic pipes connected to it.

On the corsa B the master cylinder is under the scuttle and, unlike the servo and wiper components, it is 'factory' clean however, there are no 'spanner' marks on the hydraulic unions but I must assume it has been replaced recently.

I have also tested applying pressure to the barke pedal before starting the engine. Immediately the engine starts the pedal travels down further (approx 5 cm), as is usual when a servo is working, however, when the engine is stopped the servo hisses and I can feel the brake pedal trying to return. It takes a lot of force to keep it down. When the hissing has stopped and I take my foot off the pedal returns very slowly. As reported previously I can hear gurgling while the pedal is returning. The pedal is very firm and there is clearly no air in the system.

I was hoping to eliminate either the servo or master cylinder but so far cannot.

Any ideas would be appreciated.
94 1.2 braking problem - bell boy
get an assistant to locate the gurgling
maybe its the fluid going back through the seals as the pedal comes up as its easy to damage a master cylinder on a corsa by being vehement in pushing caliper pistons back

or the pedal is coming up soonest because fluid is trapped at the wrong side of the seals

why not just replace the master cylinder with one from a scrappies and see if pedal returns properly

apart from that its a toyah question
94 1.2 braking problem - Bluesky
Definitely a servo problem. Staring the engine now causes the brakes to lock until switch off. I have obtained a used servo from the breakers which I will try in the next few days. Hopefully that will solve it and I can start on the next problem!
94 1.2 braking problem - Bluesky
Problem resolved. Old servo contained petrol not brake fluid. Replaced servo and servo hose (non return valve had failed).

Thanks for all the advice.

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