For the past few months I've been working on this car. 74 vette coupe from hell. I got the project partially in boxes. I am close to having this car ready for the road, but the brakes are now my last major problem.

When I first got the car the brakes seemed ok. I bled them at one point and then they seemed fine after that. A few months passed and the 2 front calipers started leaking. I got the seal kits and installed them. I also replaced the master cylinder since the past owner can't answer a single question about the car.

My current problem is with the brake pedal. It hangs up in the middle when the pedal is released. The booster looks new and the past owner thinks it was replaced. I removed the master cylinder and hooked up a vacuum source to the booster. It still did it. When I apply the brake and let go the pedal doesn't come all the way up unless I use my foot and then it will spring all the way up. It acts like its hung up and then pops up.

I was also concerend that the spring on the pedal might be weak, so with the booster input shaft disconnected I applied the pedal only to find that it springs all the way up. I tried it several times and it popped up everytime.

I just got thru removing the booster and applied the vacuum source to it while sitting on the bench. It doesn't seem to have any leaks, but when the shaft is pushed in and let go the shaft doesn't come back out fast every time. Sometimes it just stays in. Other times it comes back out slowly. The booster overall looks new. Does this sound like my overall problem is my booster?

 

Sounds like the booster to me. You elimanted the m/c first, then when the booster is eliminated the pedal works fine. Maybe somebody will chime in with a fix with out replacement? Sitting around brings out some strange bugs.. good luck

 

I wish I would have pulled the booster of the buick I just sent to the junk yard since it worked fine. It could have given me some clues since I've never had a booster problem before.

 

only problem I have ever seen with a booster is a rock hard brake pedal. I have seen some binding problems before but I think they turned out to be M/C or pedal pin issues.

 

The only failure I have ever seen is a hard pedal. Sounds like the MC. Did you experience this problem before you changed the MC?

 

Yes it was hanging up before.

The thing is I unbolted the master cylinder from the booster and pulled it away. The pedal still is hanging up while traveling to the return upright position. I'm basically convinced that it is something with the booster or the input shaft has something wrong with it. I just was trying to see if anyone has had this problem in the past.