So when I pump the brakes in reapeatedly, the idle lowers and will die. For the most part my brakes are quite soft unless double pumped. I have replaced all brake calipers, pads, shoes, and wheel cylinders, no leaks ive triple checked. Im thinking brake booster... any help is appreciated.

 

well, you could unplug the booster hose from the engine, block the vacuum port off on the engine side, and see if the problem happens again... also:

1)hold the brake pedal down 2)start the engine

if i remember correctly, with a working booster, the pedal should sink down(?)

there was a thread for a similar problem within the last year, with links to a document that listed the entire troubleshooting procedure.

 

If you can double pump, and pedal feels good and remains solid, more than likely there is air in the system. It's possible a bad master can give similar symptoms, but not always likely. My guess is air somewhere since it's had a good bit of stuff replaced recently, and all of the lines have been opened. If they stayed open to long, with nothing capping them, then the fluid could have drained all the way out of the master, which would need bled also.

 

I haven't yet bled the master cylinder I'll try that when I get home today.

 

While true, air in the hydraulic side (master, lines, calipers, etc) doesn't explain why it dies if you hold down the brake pedal. Sounds like your booster has a leak which is letting too much vacuum escape which kills the motor. Others have pointed out that the booster can often develop a leak after you do a brake overhaul because we often press the pedal way farther in while bleeding the brakes, which stretches the booster's diaphragm farther than usual and if it's old, cracksville.

Do bleed any air out of your system, that's a given.

Also securely plug the vacuum hose that feeds into the booster and see if you still have the dies-at-idle problem. If the problem goes away when you have taken the booster out of the equation, start looking for another booster.

 

^^ I agree, although he did state he pumps repeatedly, not hold the pedal down, and then the idle lowers and dies. In which case he is just continually creating a place for vacuum to try and keep assisting. I would think that would essentially create a vacuum leak.

Am I just retarded for thinking this?

 

One of my rear wheel cylinders has failed so I was unable to bleed it this week, it will have to wait till Monday. I should add that before I replaced ANY parts of the braking system, whenever I would hit the brakes reapeatedly at a standstill it would INCREASE the idle. Then one day the pedal was a bit softer, and about 4-6 quick pumps at idle will kill the engine. I believe as FGZ stated i might have stretched the diaphragm too far during bleeding.

 

It's very possible.

 

I have not found the post referred to in this post for a more comprehensive diagnosis procedure, so I'll just throw this out there.......

My '85 truck (22RE) has poor performing brakes and I'm having a hard time diagnosing it. The pedal relaxes when you start it, so I would assume the booster is working. On the other hand, it brakes really stiff, so something's not right. Occasionally the RPM will dip when I hit the brakes (but not consistently). This morning it did it twice when almost warmed up and pulling into a parking space, but did not do it again???

Any thoughts??

 

vacuum leak in the line from booster to intake manifold