Aloha My 1st Gen Buds!

I just changed my brake booster on my truck. I adjusted the piston to match exactly the length of the booster I replaced.

I have a problem with the brake pedal not coming back all the time, and my brake light won't shut off when it happens.

I tested it while idling and laying down right near the pedal to watch what it is doing. If I pump the brakes, the pedal returns no problem, but when I give it throttle, i notice the brake pedal slowly moving in and releasing the brake light switch. If I pump them again, it firms up and returns back fine again.

I didn't have this pedal problem before I replaced the brake booster. I had to replace the booster because it was hissing loudly, and I had to press really hard to get the brakes to work. With the new booster the brakes work effortlessly, but I have this issue with the pedal.

Could there be a problem with the new booster (Cardone rebuilt)?

Could air in the lines cause this?

Could my master cylinder be bad?

Again, it won't do it if I pump the brakes a bit, but then it loosens up under throttle. I put a bungie cord tied to the brake pedal to retrieve the pedal in the mean time.

Please help.

Jeff

 

I'd get another booster.

 

Sounds like an internal leak in the booster. It should not pull the brake pedal down when you rev it.

 

On my 4th booster and have very similar problems. No vacuum leaks no hissing ect. The last 3 were complete with a master cylinder. I pulled the m/c to see if it was adjusted correctly and they were all very close. Now the pedal almost goes to the floor. It's like on a daily basis it gets worse. I'm to the point of finding a hydravac system so i'll have brake at least good enough to stop the truck. If someone has a cure i'll sure listen. Good luck Diesel Jeff.

 

A quick and easy thing to try is just turn the adjuster screw on the booster (the one that goes into the master and works the cylinder) out a few turns.

Worked for me and you only need to take off two nuts and put them back on.

JP.

 

Maybe the check valve isn't working right?