Brake servo issue and possible linked boost issue

[slipperyox]

Hi, I had an issue where the servo leaked at the metal and I had no servo after the third brake press. This is now resolved via expoxy on the metal leak. However, if the car is left for 30 mins after running, there is no residual servo assist on the brakes (pedal is rock hard) When I start the car in the morning the brakes are solid and take a few secs to liven up! Other that that, boost is intermittent. Perhaps they are linked?

[Dan J]

If the brake servo is leaking I'd advise replacing it rather than trying to patch a leak up especially where brakes are concerned, it sounds to me like you've still got a leak in it.

[slipperyox]

Thanks dan, i will try to isolate the servo with a mighty vac, and test it for a leak

[Alan02]

Check the plastic servo hose also, as a crack would cause a leak too. Ans also check the off-takes from this hose.

[slipperyox]

I have used suds to check for leaks in the past, was thinking if this is safe now.....................?

[Alan G H]

Use suds by all means, but you won't see any bubbles, as you are looking for vacuum leaks, the bubbles will all be inside the pipes or components!! You will have to listen carefully for leaks. Maybe I missed it before, but what car is it? Petrol or diesel?

[slipperyox]

b5 a4 tdi avant quattro, i used suds before to find the big hole in the servo, it made a noise as it was sucked in!

[Doctle Odd]

This is a common problem with A4's and Passats. There are several write-ups available showing how to change the servo, this is a safety critical issue and the servo should be replaced. It's a couple of hours well spent replacing it. you don't want a rock hard pedal in an emergency.

[slipperyox]

Assuming its the problem, will a passat one from the same era fit?

[Doctle Odd]

As far as I know theyre the same. This problem has been talked about for years,the easy cure was a wire coat hanger when you did your weekly checks. The plenum chamber fills with water can't drain and rusts and rots the bottom of the servo. It's not too hard to change just a bit time consuming if you do change yours its a good opportunity to change your brake fluid.