Join Date: Jul 2009
Location: Sault Ste. Marie, Ont., Canada
Rep Power: 0
I didn't catch your previous posts so bear with me here. It seems you're having multiple vacuum issues. This post mentions multiple leaks on a line from the breather box. These leaks are outside of the throttle body and should not affect idle or cause an major performance problems. You also mention a low brake pedal condition at low rpms. Your engine should develop its' highest vacuum at idle or deceleration so the low pedal should be the result of maximum boost.
The brake power booster is essentially a large vacuum servo. It is basically a vacuum tank with a diaphragm in the middle. When you step on the brake pedal it causes a valve close off the diaphragm and open the back of the tank to the air. Atmospheric pressure pushes the diaphragm in the same direction as the pedal push. I explained all this so that you will understand the next part.
Your post said you could hear a constant vacuum hiss. It also said that your brake pedal goes down further at low revs. It is possible for your vacuum booster to fail if that valve fails or the diaphragm splits. I don't know if you are having any problems with idling but it is possible for the booster to fail without causing noticeable idling problems.
If your booster is functioning properly your rear brakes may need attention and that could cause the drop in pedal height. If the brakes are severely out of adjustment, or if there is air in the system, the master cylinder could be near the end of its' travel range.
Sorry for the rambling post but I see a potential safety issue here and I don't have all he information to work with.
Good luck, Popeye