Stiff brake pedal under boost...

[Toxa]

Good evening.

I have strange problem on my 2001 S3.

If you need to brake right after car goes under the boost (sudden stop), brake pedal gets very stiff, like booster is not working, but after a moment pedal gets back to normal.

I've changed valves, checked vacoom lines, but fiound no leak (maybe just missed it).
Have anyone experienced such a problem?

Thanks in advance.

 

[Grale1]

I thought I was the only one who had this problem also

 

[ayfreetee]

Sounds like a servo problem, maybe a split diaphragm and not holding vacuum.

 

[Lewis583]

Check the one way valves in the vacuum supply line to the brake servo.

 

[Toxa]

I'll check them on saturday, thanks. I hope i'll find that problem, because Brembo 6 piston calipers & Mk4 R32 rotors are waiting to be installed