After replacing the left front leaking caliper and power bleeding all 4 wheels. I still cannot get a firm brake pedal on the 82 with power brakes.  The pedal goes to the floor with the engine running.  The pedal is firm with the engine off. This is the first time I have ever used a power bleeder.  I had trouble getting it to seal on the master cylinder.   I power blead the brakes with the engine off.  Questions, can the master cylinder be leaking air even if it is not leaking brake fluid?  Do you have the engine running using a power bleader?

 

I worked on it all weekend, and have no idea what to do next.

 

Thanks for any advice.

 

If you have a loss of brake fluid, look under the brake booster and see if there is any fluid dripping.  It might be the booster.

[QUOTE=1982CE] [/QUOTE] If you have to change the power booster...........you definitely have a treat in store for you. Yes there are 4 studs protruding thru the firewall. To access the nuts is an act for a contortionist. The best way is to remove the driver seat. Now you have lay under the dash with your neck just about ready to snap. You need a weird array of tools to get to the top two nuts. This job can hurt you for days.........trying to recover from your strained body. I'm not trying to scare you, just warn you about it. I really hope for your sake that you don't have to this. Good luck!!!  corvette440hp2008-10-06 14:53:29

The booster is just a power assist, if you are loosing fluid it will be a MC.

I just changed the front breaks rotors and pads. I picked up a set of speed bleeders from auto zone. They worked like a champ! You replace the ole bleeder valve with these. They have a small bearing so you dont have to close the valve every time. Still neede someone to pump for the reer breaks but for the front the bleeders worked good. Also cheack to make sure that your cover is sealing all the way for MC. Mine looses fluid because it does not seal all the way. A change that will be this winter.

What does a perportioning valve do?  What are the symptoms when they go bad?

 

If you have a leak in the the front brakes, their is uneaqual pres at the valve. It shifts position to block fluid from the MC to the leaky brake so you do not loose all brakes, just front or rear. on my 77 when it  set itself like I described it turned the break light on my center panel on. The light will not go out until it is reset. When I first had this problem I had trouble getting it to reset, the two man pumping the breaks did not do it. I t did not reset until I used a vacum bleeder. I am not sure what the symptoms of the valve being bad would be other than obvious leaks or front or rear brakes not working. Maybe some else will have some ideas 

The brake light on the center panel is not on so I wonder if the proportioning valve is ok.  Maybe I should start by replacing the Master cylinder, then the proportioning valve.  The brake pedal is firm with the engine off.  Could it still be bad?  I don't think it is leaking.

There are other indication, but when I have had a MC bad, you can pump the breaks up and then on the last pump hold the pressure and instead of holding the pedal will gradually bleed down.