I have a 1989 Z24 Convertible - 2.8 Auto. Recently replaced the Master Cylinder, Front Calipers and 1 rear wheel cylinder. (other one was fine). After bleeding several times, and the dealer attempting to bleed, and replacing the master cylinder again (After Marklet Part) the pdeal goes straight to the floor when the engine is on. When the engine is off, the pedal will stiffen with repeated depressing. Any Ides???

I'm not saying to replace it , but, it might be the brake booster leaking. I'm not sure of how to check it though.

Hi, Thanks for the reply. I discussed that possibility with the dealer, they stated that a problem with the booster should result in a harder pedal. Also, after the car has run for a period of time, a vaccum is created in the booster. When you remove the vaccum line to the booster, there is a significant pressure release. I will discuss with them again though, you got me thinking maybe there is too much vaccum....

Thanks Again

I have seen that happen if the brakes still have some air in them.When the booster loses its vacuum reserve it sorta fakes you out when it goes solid,but there still may be next to no brakes.I would say re-bleed all 4 wheels,as any time you replace a master cylinder there can be air trapped between the master and any of the 4 bleeder screws.The pedal should be solid,not mushy or low under any circumstance.