'91 Z28 5.7L w/ front & rear calipers. I replaced front & rear hoses (all 3 in the rear & rear brake lines as well). New stock calipers in the front and just cleaned up the rear calipers and put them back on. Replaced the fluid in the master cylinder (at least what was left since it was very dirty). Bled the brakes until the fluid was clear at all four calipers and no bubbles. The car is still on jack stands so I ran it through all the gears to top of the transmission fluid. That is when I noticed the rear brakes will not stop the wheels from turning. I can get the wheels to stop if I pull the E-Brake all the way up (so I could get the transmission back into "Park" . I also noticed that when applying the brake pedal, the brake fluid in the reservoir jumps up (like the fluid is pushing back into the master cylinder reservoir). No bubbles, just appears that the fluid is moving inside the reservoir. Is this normal? If not, what is causing this to happen? Could this also have something to do with the lack of braking in the rear brakes?

 

Actually both issues are normal. The brake fluid moving in the M/C is due to the compensation ports. Need to be careful that you don't spray fluid out as it is an excellent paint remover.

As for not stopping the rear tires. The rear caliper pressure is weak due to the proportioning system of the combo valve. Some folks use a different spring in the combo valve to provide more pressure to the rear brakes. But need to be careful as locking up the rear brakes before the fronts lock usually causes the car to do a 180.

RBob.

 

Thank you RBob. I rebuilt the left rear caliper (seemed like it was not functioning). 1LE aluminum single piston calipers. New rear rotors and brake pads. Bled the brakes one more time. Brakes and parking brake are working like new!! Just thought I would give an update. Thanks for the help.