2nd Gen Non-Engine/Transmission Master cylinder bench bleed or not.

[SMalafy]

I just replaced my main seal on my hydro booster and had to disconnect the master cylinder lines. I hooked everything back together again with out bench bleeding the MC figuring my Motive power bleeder would take care of that. Filled everything up bled brakes and hydro boost but now I have a squishy slow to return brake pedal. Not sure if failing to bench bleed the MC is the problem or if I have something else going on as I am sure I got all the air out of the brake lines. ABS and Brake light is lit up on dash but it was that way before I did the hydro boost main seal. Hoping I do not have to remove the MC just to bench bleed it. I just think I am missing something here.

 

[petersonj]

I am assuming that you re-used the push rod between the brake booster and the master cylinder. Did that part of the re-assembly go like it should? Specifically, when you installed the master cylinder, did the master cylinder slide freely up to the face of the brake booster without energizing the piston in the master cylinder? There must be free-play there. Since this cannot be seen, it has to be noted by feel. If the brake master cylinder piston is pushed in over 1/16th of an inch, the compensating ports will be covered and no fluid or trapped air will be allowed to return to the reservoir.

If you think there is air in the master cylinder or right at the master cylinder fittings, you can depress the brake pedal just enough to engage the slightest movement of the master cylinder pistons, and then release. This repetitive action will agitate the fluid / trapped air and let it release through the compensating ports into the reservoir. You will need to do this action 30 to 50 times. It may take a bit time to get the feel. If the pedal slowly starts rising, then you have resolved the issue. The engine does not need to run for this exercise.

- John

 

[SMalafy]

I am assuming that you re-used the push rod between the brake booster and the master cylinder. Did that part of the re-assembly go like it should? Specifically, when you installed the master cylinder, did the master cylinder slide freely up to the face of the brake booster without energizing the piston in the master cylinder? There must be free-play there. Since this cannot be seen, it has to be noted by feel. If the brake master cylinder piston is pushed in over 1/16th of an inch, the compensating ports will be covered and no fluid or trapped air will be allowed to return to the reservoir.

If you think there is air in the master cylinder or right at the master cylinder fittings, you can depress the brake pedal just enough to engage the slightest movement of the master cylinder pistons, and then release. This repetitive action will agitate the fluid / trapped air and let it release through the compensating ports into the reservoir. You will need to do this action 30 to 50 times. It may take a bit time to get the feel. If the pedal slowly starts rising, then you have resolved the issue. The engine does not need to run for this exercise.

- John

I think I found my problem. The parking brake lever in the rear drum knocked the retaining lever to the star adjusting wheel off and I guess the adjuster backed off all the way off causing the shoes to have no adjustment. I can adjust them back up again but I am wondering about knocking the retaining lever off again when I apply the parking brake. I must of had routed the cable improperly so now I need to figure out how to route the cable to the adjuster on the wheel so the parking brake lever will not knock it off of the star adjuster wheel again. Very frustrating. THANKS FOR THE REPLY THOUGH