i just completed a brake overhaul on my 85. in a nutshell, i installed new front and rear rotors with ceramic pads (irotors), rebuilt all four calipers (ac delco rebuild kits) w/ speed bleeders, installed a new master cylinder (ac delco), and installed goodridge s/s brake lines. the bleeding operation went fairly smooth, but i did have little trouble bleeding the mastercylinder, and i'm beginning to think the master cylinder is source of my problem. i went through the bleeding process twice RR, LR, RF, LF. when i first finished the brake job, and test drove the car, my brake "idiot" light came on initially, but went out after i pumped the pedal several times. it hasn't come on since.

my braking seems to be about 80/20 front to rear (i'm guessing). from the wear pattern on the rotors, the front seems to "grabbing" OK - car stops as expected under normal driving. it looks like the rears are not engaging as expected. the rear wear pattern looks like the pads are engaging slightly, but the rotors dont have that shiney-smooth look. under hard braking, i'm also getting a one-per-rev clicking sound from the RR assembly only when hard braking. i disassembled the RR and inspected everything, and everything looks OK. i went through the bleeding operation a third time (rears only). i'm thinking i might have a air bubble trapped in the master cylinder (rear circuit). as far as the clicking sound under hard braking, well, i'm stumped - ??? i'm thinking about taking it into the shop for a power bleed - ??? HELP!!! comments - TIA and

 

just got off the phone with the service guy at my local chevy dealer. he indicated there should be some sort of COMBINATION VALVE on the left side, under the master cylinder that has some sort of "button" that needs to be depressed that allows hydraulic pressure to the rears. THIS IS A NEW ONE ON ME - i dont recall seeing any additional hardware on the rear brake circuit - ?????????? again, any help - ???

 

There is a combination valve, but you didn't mess with it. How hard is the pedal with the engine off? How much pedal travel?

That warning light went off because you had a bunch of air in either the front or rear circuit.

I don't think the combination valve needs to be reset.

 

thanks for the reply. ...still lost - where is the combination valve? i've always understood that the combination valve circuitry is part of the master cylinder - ??? either i'm looking right through this damn thing or i dont have one - ???

the pedal feels hard with the engine off, with minimal travel. that part seems OK.

am i to understand that the warning light went off because i had a bunch of air in the front or rear circuit? shouldn't the light be on when there is air in the system or low hydraulic pressure when applying the brakes - ???

the rear noise seem to be gone this morning. i drove the car to work, and didn't hear that one per rev clicking. i'm going to check again on the way home. i'll take the back roads where i can get into some serious braking.

think i could still use some help...