# hard brake pedal. booster vacuum line issue?



## bavareze (Sep 15, 2009)

Hello,

I have 99 Audi A6 with V6 ATQ engine. I have a brake issue:

after driving normally (accelerator 50% => low vacuum in manifold) the brake pedal is very hard = no boost.

if I let accelerator pedal go for few seconds ( = lots of vacuum in manifold) then the brake pedal is again normal.

what I am guessing is that a certain valve that is supposed to trap the vacuum in the booster area is not working properly. so whenever accelerator is open the vacuum is lost.

any idea which valve might be bad? or any other ideas?

thanks


----------



## GTijoejoe (Oct 6, 2001)

OK, let me get this straight... you don't have good boost assist, the transient time between idle, to 50% throttle to brake yeilds no boost...... from idle to 50% throttle, back to idle = boost? 

You may have a leaking booster or your check valve needs replacement, probably I would check the check valve first, your booster seems to be losing vac. over time. Worst case you'll need to replace the booster, you can also check to be sure your pedal is at 0 stroke, try pulling back on it to release, see if there is motion.


----------

