# Brake Pedal Issue (Stiff Pedal)



## nemo1ner (May 5, 2004)

I have been experiencing a hard brake pedal issue. Not while normally driving, but while autocrossing. 

When braking hard initially, the brakes work as they should; however, if I accelerate and get hard on the brake pedal again, it becomes stiff and will not depress. I am thinking that it's a vacuum issue (maybe a leak in the line leading into the booster). I am just curious if others experienced it, if it's a common issue, and what corrective measures were taken. 

I have heard a few B5 S4 owners also have the same issue, but I don't know if it is also common on the TT. 

Any advice will be greatly appreciated. :thumbup:


----------



## 20v master (May 7, 2009)

Clogged/failed suction jet pump in the PCV system? This ties into vac being used for the brake booster. Max runs a second vac source with a check valve to the turbo inlet as it's always under vac and this helped him during Auto-X. I'm sure he'll chime in with why he did it and the results.


----------



## nemo1ner (May 5, 2004)

20v master said:


> Clogged/failed suction jet pump in the PCV system? This ties into vac being used for the brake booster. Max runs a second vac source with a check valve to the turbo inlet as it's always under vac and this helped him during Auto-X. I'm sure he'll chime in with why he did it and the results.


 Thanks for the info. Hopefully he can guide me in the right direction. It's very frustrating, and once it happens, I Jedi mind-**** myself for the remainder of the run and simply get too sloppy.


----------



## Marcus_Aurelius (Mar 1, 2012)

Yes Sir! Our vacuum system is so over-complicated with long lines and useless bypasses that in competition, if you're fast enough with the brake/throttle pedal transition (or left foot brake like I do), you will experience the "wooden" pedal syndrome. It is scary if you're inexperienced and was not trained to stand on the brake pedal to compensate for the lack of vacuum assist. 

What I did to solve the problem is the simplest and oldest trick in the book of tracking turbo cars. Just route a vacuum signal from the TIP which is always in vacuum while running, and "T" it into the brake booster line. Place your T after the existing check valves or place a dedicated check valve in your new signal source. I used a TIP from that has an extra nipple to have a clean vacuum sources, but you could share a signal and still get plenty of vacuum for the brake assist. Another thing you could do if your signal is a bit weak, is place a small vacuum tank inline to store some vacuum for when it's needed. :beer: 

Have you experienced the brake/throttle overlap fuel cut yet? Now that is frustrating because it totally ruins your runs.


----------



## nemo1ner (May 5, 2004)

Marcus_Aurelius said:


> Yes Sir! Our vacuum system is so over-complicated with long lines and useless bypasses that in competition, if you're fast enough with the brake/throttle pedal transition (or left foot brake like I do), you will experience the "wooden" pedal syndrome. It is scary if you're inexperienced and was not trained to stand on the brake pedal to compensate for the lack of vacuum assist.
> 
> What I did to solve the problem is the simplest and oldest trick in the book of tracking turbo cars. Just route a vacuum signal from the TIP which is always in vacuum while running, and "T" it into the brake booster line. Place your T after the existing check valves or place a dedicated check valve in your new signal source. I used a TIP from that has an extra nipple to have a clean vacuum sources, but you could share a signal and still get plenty of vacuum for the brake assist. Another thing you could do if your signal is a bit weak, is place a small vacuum tank inline to store some vacuum for when it's needed. :beer:
> 
> Have you experienced the brake/throttle overlap fuel cut yet? Now that is frustrating because it totally ruins your runs.


 Holy crap, YES! There were times where the car would just drop RPM's. Mainly when left-foot braking like you said. I would brake with the left while maintaining a bit of throttle in order to pivot the car through the turn, but when exiting, the engine would cut out and the car would just bog momentarily. 

I have learned that I can't toss the car around as much as I would like, and have learned to drive slower to go faster, if that makes any sense. But even driving smoothly, these issues come up.

It definitely messes with my momentum and concentration. Once it happens, I simply get angry at myself/car and try to make up time lost by going faster. Unfortunately, that reaction does the exact opposite. 

Thank you for your response! :beer:


----------

