Hello, I recently replaced my master cylinder and when I was bleeding the system I had some weirdness happen.
First I bled the MC on the bench, I have the kit with the tubes, after several pumps the air was gone and it seemed like good pressure, I installed it on the car and had pretty good pedal right away (about 1/2) so I started the bleeding sequence RR, LR, when I was about to do the RF the pedal just went all the way to the floor and would not pump back up, just kind of limp feeling, pumping would not produce any more pressure to try to bleed. OK the MC went bad, new unit from Napa, so I returned it for another, I went to bench bleed this one and it won't move any fluid out of the outlets, but if I submerged the tubes into the fluid it eventually built up pressure, installed it on the car and it will not produce pressure, I thought maybe I didn't get all the air out, so when I went to bleed the MC again I noticed that it would push fluid when the pedal was pressed, but when released the fluid would suck back into the tubes. I have never seen that happen, so I guess my question is... is it possible to get two bad units in a row? or am I doing something wrong here? I have replaced MC's before and never had anything close to this happen. Ideas? Suggestions?

I would take it back for a replacement. :yes:

I had two remananufactured master cylinders to go bad so it is possible. I've never bought a new one so I don't know if they can go bad so quick.

It took three tries before getting a good master cylinder to work on our '69 el Camino. Never mind that the one that was on the car when we got it was leaking into the brake booster. It was half full of brake fluid.

Go get a new Master Cylinder from the dealer, sounds like yours took a crap. I just had the same problem on my 70 yesterday, I should have just went right to the new one the first time, so much time waisted!

BIG-C