rock hard brake pedal

[bobby1966]

hi i'm new to all this but can anyone help me i have an A4 1.9tdi (2002) my brake pedal has just gone rock hard. a friend said something about vacuum pump failure or check the plenum valve. i have no idea where these are located.

[Marco34]

hi i'm new to all this but can anyone help me i have an A4 1.9tdi (2002) my brake pedal has just gone rock hard. a friend said something about vacuum pump failure or check the plenum valve. i have no idea where these are located.

sounds like the vaccum assistance is not working. Worth checking the plenum chamber. It is easlily removable. The strip of plastic where the battery cover is - all this comes off. Undo the rubber engine compartment seal strip and then pull the plenum cover towards you away from the windscreen. This will reveal the battery, servo, brake fluid reservoir etc. check there is no water settling there. It's quite common on these cars. Failing that, I'm not too sure as I've never delved into the vacumm assistance.

[Crasher]

Could be the vacuum pump or the supply pipe or even a water damaged servo.

[bobby1966]

sounds like the vaccum assistance is not working. Worth checking the plenum chamber. It is easlily removable. The strip of plastic where the battery cover is - all this comes off. Undo the rubber engine compartment seal strip and then pull the plenum cover towards you away from the windscreen. This will reveal the battery, servo, brake fluid reservoir etc. check there is no water settling there. It's quite common on these cars. Failing that, I'm not too sure as I've never delved into the vacumm assistance.

hi thanks for that i have checked the plenum chamber and it was full of water so i removed debris and all the water flushed away out of the bottom. the brakes are better but they are still quite hard, is it possible for the water to get into the pump itself ?

[Hex69]

hi thanks for that i have checked the plenum chamber and it was full of water so i removed debris and all the water flushed away out of the bottom. the brakes are better but they are still quite hard, is it possible for the water to get into the pump itself ?

Yes, it rusts the internals. See here, A4s, A6s, and Passats, of a similar age are all affected.

[bobby1966]

Could be the vacuum pump or the supply pipe or even a water damaged servo.

hi where is the pump or supply pipe located

[Crasher]

If you can see the servo you can see the pipe! The pump is on the back of the head. I imagine your servo is full of water and if it is you will need a new servo and master cylinder.