I recently installed Earl's braided lines on my 90 with 4-wheel discs. The install went fine, I flushed the lines, bench bled the master cylinder, pressure bled the entire system and seemingly removed all of the air. The pedal is rock hard with the car off. However, when the car is running the pedal seems soft, and with the rear end jacked up the brakes can't stop the rear wheels from spinning at idle (although it comes quite close). Is that normal or should it lock the rears when jacked up? What would cause the pedal to go from rock with engine off to soft with engine on?

I am able to lock the front tires driving, but am concerned the rears may be not functioning correctly.

I bench bled the master cylinder level in a vise, and pressure bled the system with teh rea end jacked way up. I have bled and re-bled, then bought the Maxi-Ject and re-bled everything again so am hesitant to think thats the problem.

 

Possibly a bad proportioning valve? I don't have much expierence in brakes but that might be it.

 

It has been deemed normal for the rears not to lock the rear tires while in gear on jack stands. However there is a prop valve modification that can be done to increase the pressure to the rear brakes. do a search on prop valve and you should find the mod.

 

is the pedal soft while in park? how about while you driving around and use the brakes then? how does it feel then? if it feels normal/stiff you are ok. my brakes feel the same way. you just might have a tad of air still trapped some where in the lines.