Yotapup

Having trouble bleeding brake system on 89 P/U, I bleed the master cylinder and install,but as soon as I hit the brake pedal i lose prime on the system(no flow from master cylinder).I have tried gravity bleeding and about anything else I can think of.Worst time i have ever had trying to bleed a sytem.Had it close to bleeding one time: Back was all primed but as soon as I moved to front I lost prime,now I can't even get the back to prime.Help!!
Also,I pulled the Brake booster and have no obvious leaks!
Also ,The pedal goes straight to the floor and can not pump it up.This is the 3rd reman. master cylinder.

mattaway

did you check the wheel cylinders for leaks? maybe a cracked line somewhere?

Yotapup

I have not been able to find any leaks,either on the wheel cylinders,calipers or any lines. Any other ideas out there?

metalhed

Most likely bad master cylinders. I know 3 bad ones in a row, but it could happen.

Try a new master cylinder and get a power bleeder.

Yotapup

By power bleeder are you talking about the auto. vacuum tester/ bleeder?If not let me know what kind. I have one that will bleed master cylinder well, but just pulls too much air at the wheels even after a gravity bleed on the system.
I have not been able to use the pedal pumping method b/c I have no pedal resistance.Makes it kinda hard to bleed.

Yotapup

After the 4th master cylinder I finally found a good one!!!