My dad has a 97 Jimmy, 4.3. He did not have any brake and I determined it was the Brake Booster. Replaced that with one from Adavance and now the pedal will go to the floor when you press on it hard and the pedal stays, holding the brakes on. I hear a whistle when this happens. After a good 15 secs the pedal slow comes back. My next step is to replace the vacummhose from the brake booster to the intake. Also is that a check valve at the intake or just a fitting.

Thanks!

 

if the pedal is going all the way to the floor without it stopping it will probably be leaking brake fluid or a bad master cylinder. usually when those boosters go bad you just lose your power brakes making the pedal really stiff.. check the fluid level and underneath for leaks

 

+1, sounds like there is serious air in the system. If the master has air in it, you will have to take it to a dealer so they can hook up a computer to it to bleed it.

 

Well no brake fluid leaking from any of the wheels, Front disc and rear drums. Bled the system and very little air in it. The problem is still there. I push the brake pedal in and it will stay in. It appears to be under pressure to stay in, almost like a vacuum is holding it in. I removed the check valve in the Booster and the pedal immediately came out. Next thing I am going to try is a new vacuum hose and valve connection at the intake. If that is not it I think I may have gotten a bad booster.

My dad just mentioned to me he was driving with A/C on and it seemed like the car did not have any power, ran really rough. This all started the sametime the brake issue started. Not sure how they would be related.

 

Well repalced the vacuum hose and fitting at the intake and still same issue. When the pedal is pushed in it stays in, under vacuum. Only other thing is to try a new booster.

Anyone have any other suggestions? Could it be the ABS Unit? I am not getting any codes, ABS or otherwise. Any other vacuum source that may be causing the problem? I did notice a number of the other hoses under the hood are dry rotted so we are replacing them also.

Thankd everyone for your help!

 

you didn't put the check valve on backwards.. did you?

 

Well solve the brake issue. the NEW Booster was bad. Don't you love it. Of Course Advance exchanged with no problem but it is the idea. Nice thing is it only took me about 40 minutes to change it this time where the first time took me about 1.5 hours.

 

40 minutes instead of 1.5 hours... Repetition does caused efficiency but I think you could have lived happily without becoming more efficient at Booster replacement. Guarantees are fine but they never include Labor. Not great when rebuilding a Trani or something truly Time consuming.
Glad you got it squared away.. Being able to stop is always good

 

Huh? I've never seen anyone do that and Im a tech at a GM dealership.

 

I'm assuming he's joking.