while doing some spirited driving today my brake assist disappeared altogether. the car still slowed down but took alot of space to do it and a LOT of pedal effort.

upon arrival at home my dad and i checked around and did some testing as per the haynes book and the diagnosis is that the brake booster is bad. this is evident esp because the idle drops like 600RPMs every time i get on the brakes lol.

time to go buy a new one and swap that f&cker out.

 

I think another test is to put your foot on the brake firmly with the car running, then turn the car off. If the booster is WORKING, the pedal will drop about 3/4 inch. I had a shop tell me that my booster was bad last Fall. The car was in for other work, so I did not authorize them to change the booster. After getting it back, it passed the diagnostic and has been fine ever since.

 

another thing; while holding the brake pedal for the last week or so, even under moderate pressure (just enough to keep the car still at a light) i can hear the hissing sound of vacuum, on full pressure or very light pressure you cant hear it but everywhere in between you hear it leak.

 

Have you checked for vacuum leaks?

 

I tend to think brakes are important.

 

The booster works off of vacuum.

 

yea i did the water test and none of the lines were leaking. i ran the car and pulled the vacuum line off of the brake booster and plugged it and hit the brake, it ran perfectly. when i plugged the line back into the booster and hit the brake again the idle dropped to about 600 and sounded like it was knocking lol. the lines are fine and tight.

 

I drove my 944 around for months with no power booster. I actually liked the pedal feel better without them. When I finally fixed the brake system I couldnt get used to the power, kept stomping on them and giving all the passengers a headache. lol

 

My mech was driving mine right after getting my engine back in- he said that while on-boost, the hose popped off where it connects at the valve cover. Scared the hell out of him, as he barely stopped the car. He said he could not believe the factory did not thread the line there. I never knew anything about it. Is there any way to ensure this line does not come loose? Has this ever happened to anyone here? Spencer- are you sure your's didn't do something similar & was not a bad booster?

 

i checked the vacuum lines, all of them. however upon replacement of the brake booster (and some fresh fluid ) the brakes work even better than when i bought the car. nice firm pedal and goddamn this thing stops from speed FAST.