Hey guys. My brake pedal goes to the floor and I barely have any breaks. I have checked the booster and it is functioning properly and has good vacuum from the manifold. I replaced the master cylinder. I bench bled it and installed it. I bled the brakes and they are all moving fluid steady and it’s clean. I went for a test drive and the brakes still suck and had no change. I have no idea where to go from here. Could anyone please help?

The car is disc in the front and rear.

 

I moved your post into its own thread instead of resurrecting an unrelated old one. Did you make sure that the booster actuator pin matches the new master cylinder? If you pump the brakes do you get a higher pedal?

 

Exactly which M/C, booster, and combo valve do you have? There are really only two reasons why this happens with a new M/C (OK, three if the brand new M/C is bad - possible but not likely). The two reasons are 1) you still have air in the system) or 2) one of the pushrods (pedal to booster or booster to M/C) is the wrong length, preventing the M/C from working properly. I'm betting on air.

 

That’s what I’m leaning towards as well. I still have the original GM booster. All the research I did told me to get the M/C I got. It’s from Auto Zone. The brake feels firm until I turn the car on and once vacuum is introduced it sinks and became very soft.

 

I think it's still got air in the system.

 

Where else will I be able to leak air out of? Could there potentially be a hole in line somewhere? I have good flow at all of the calipers and no bubbles. I have no bubbles in the M/C either. I do hear a lot of air when I press the brake pedal. Could that be the cause?