1980. I bought this car recently.po had changed out brake mc,but ended up with soft pedal.i have power bled brakes twice without any change in pedal firmness.

What are my options to get air out of mc.there is no bleeder nipple on mc.

 

Do you have a MittyVac? Try bleeding the system with new fluid and see what results are, at least you will know it is done correctly.

I have only ever once bench bleed a MC. And I did it to see what all the fuss was about, no better results then when I installed and vacuum bleed the brakes.

Have the lines all been replaced with the MC? I know my 80 had cracked the lines and slow fluid leaks.

 

Any air trapped in the system is at the MC and will require basically bleeding all the fluid out to remove the air. It's probably due for a full fluid flush anyway.

Bleed each caliper until you get fresh clean fluid out. That should take care of any air bubbles. A few taps with a rubber mallet on each caliper at the end of the bleed helps dislodge trapped air bubbles.

Don't forget to also bleed the clutch slave cylinder if it's a manual. That fluid tends to get over looked.

 

Do the bench bleeding to get the air out of the top front of each section of the MC. MC is level in a vise, each outlet port is piped back into the reservoir. You use a screwdriver to push the rear piston multiple times until no bubbles return to the reservoir via the tubes.

Remember that the early cars like yours have diagonal brakes, with each of the two pistons connected to one rear and one front caliper. Follow the bleeding sequence in the WSM for early cars. It's not the same as the later cars, or the convention of starting at the furthest caliper and working towards the closest one.

 

I had that exact situation just prior to Sharks in the Mountains. First thing to do is open the bleed screw on the master cylinder. That burped out a lot of air for me even after power bleeding etc. The second thing to do came from a fellow SITM attendee. Get a pump oil can, fill it with brake fluid, and pressure bleed from one the driver's front caliper back to the MC. Air wants to rise and this will force it out the top to the reservoir.

 

The early car MC is significantly different from the one in your GT. Early cars have diagonal brakes, and use hydraulic coupling between the front and rear MC pistons. There's sort of check valve as part of the piston that lets the two circuits balance pedal force. It takes some specific bleeding and flushing procedures. Doing the bench bleeding purges air out, and at least as important it gets the two pistons in their correct relative position. It's quite important to follow the WSM bleeding procedure exactly.

 

unfortunately I do not have the wsm.would you be willing to describe the caliper bleeding procedure unique to early cars?

 

just ordered cd set from roger

 

Sorry I'm not near the WSM set. Or I would have shared.

 

Thanks so much. You mention opening the tip. What is that?

 

This is an update on my soft pedal.turns out that the "new" brake master the po put in was pos made in some third world country.replacing with new one cured the problem