I'm getting no pressure in my brake pedal. Gets pressure and holds when off but when on it wont build. Master is good pads and shoes are good. Lines are new. No leaks anywhere. Fuses are good. And system was bled. Abs and brake light are on. And it has fluid. Any thoughts? It's a 99 durango with a 5.2l 318 ci motor.

 

Sounds like you either have a leak or still have air in there, quite possibly in the abs system. How do you know the master is good?

 

I pumped the pedal with vehicle off and held it. It did not sink or lose its pressure. Which is a sign of the master being good. After reading up some more. There is a hissing. And supposedly that means the booster is bad. I will change that later and see if anything is different. And as for air in system. I've cracked and bled everything and am getting nothing but solid streams out. But it's not spraying or pressurized like it should be.

 

Do you have 2 wheel or 4 wheel abs? You won't be bleeding the whole abs module just pumping the pedal, so you could still have air in it.

 

With the engine running, you can put a LOT more pressure onto the master cylinder by pushing the pedal. Whenever I have seen those symptoms, I either have a leak somewhere, air in the system, or the proportioning valve is displaced. Which end of the system did you actually have open??

 

All lines were replaced. Its 4 wheel abs. I cracked and bled the lines on the abs module. Everything has fluid and no air.

 

You can believe what you want but if you didn't cycle the abs after replacing the lines at it, there is probably air in it. Abs pumps have lots of channels, accumulators, and so on where air gets trapped. The correct way is to use a drb3 tool to cycle the abs. Sometimes you can accomplish the same by activating the abs on a low grip surface like gravel or wet grass.

 

Assuming you have enough brakes to get somewhere you can try it, and enough brakes that they will try and lock up......

Shouldn't the motor controller go thru a self-test at initial startup? (assuming there are no permanent codes stored.....

 

I cant find any viable leaks. I sprayed the vacuum lines with a propellant and no changes in engine idle. So vacuum is fine. There is a hissing noise when you press the pedal up by the booster and master.

 

Not sure, I don't have the 4 wheel abs. He does mention having an abs light on. It would help to know what the code for that is. Not sure if the brake light is on because of the abs or because of the proportioning valve being tripped. Not backstory to what happened to lead to all the lines being replaced either.


The vacuum leak is probably inside the booster.