Ok...so I have read every thread posted, and that has been posted,that deals with bleeding brakes on our beloved Vettes. I have replace the m/c (bench bleeding first, of course), replaced all flex lines, and started with the basic pumping method on my '82CE. I soon realized that this wasn't the way to go as I was getting very little fluid (if any) out of the rears. I then borrowed a vacuum bleeder and it didn't help out very much either. I then obtained a pressure bleeder, pumped it up to 15psi, and still got marginal fluid (with some air) out of the system. All this was done with the engine off and the vacuum canister bled down. Gravity bleeding yielded very little, if any, fluid out of the system. I also had problems in getting a tight seal on the m/c with the pressure bleeder, and before i knew it, I had 1/2 quart of fluid in my garage. AARRGGG!!!!!!! From what I have read, is seems as if the p-valve is shifted preventing me from bleeding either the fronts or the backs, as it does seem to flow good fronts-no backs, to good backs-no fronts as far as fluid flow. Since the car is up on jack stands, I feel it is unsaf e to drive the car to "reset" the p-valve. Does anyone think I may have a bad p-valve, or is there a mechanical way to recenter the spool in the valve, or a way to work aroung it? The brake light is not illuminated during this process. I was able to get about 1/2 a pedal that was relatively firm, but starting the engine and energizing the stock vacuum brake booster, the pedal went completely to the floor. There are no leaks in the system anywhere and the engine is 100% stock. I am open to any and all suggestions. This has been driving me batty since I bought the car (with the brake issue) on Memorial Day. HELP....ANYONE!!! What do you gearheads think? I have works on cars years ago professionally and have never encountered this problem. Thanks, guys, in advance, for taking the time to read my plight.

 

By design, the proportioning valve will NOT inhibit fluid flow if it is in the failed mode (you'd never get it centered if it did). If the light is not on, then it has not tripped (unless there is something wrong in the wiring). Did you bleed at all the bleeder screws on the rear calipers? Inner and outers.

 

Andy, to check the valve wiring, ground the contact connected to the valve and turn key on. Light should illuminate. If it does illuminate re-connect proportioning/combination valve, the light should extinguish. Continue to bleed, as described below; like a madman until pedal pressure is up.

If the light, while testing by grounding the contact; does not illuminate with the key turned on you have a wiring issue which must be resolved before you can completely test and service the brakes.

Once satisfied that the light functions properly, to recenter the proportioning/combination valve the system requires a rapid and firm brake application once you have fluid in both the front and rear brake lines. Recentering will be evident with the extinguishing of the dash warning light.

In all likelihood if your light is not currently illuminated at this time then you may have re-introduced air into the system through the master cylinder. It is imperative that the master cylinder not be allowed to inject air during the bleeding process. I would check the light operation, then remove the master cylinder and re bench bleed until satisfied that there is no air left in the master cylinder then continue to bleed the system ensuring that the fluid always remains at the top of the reservoir. Once completely bled it is easy to siphon off the excess fluid in the top of the reservoir to maintain correct level.

Keep at it.

Dan

 

Andy, I received your PM and responded by PM moments ago.

Keep bleeding with a mallet!!

 

The p-valve is just a dumb switch. i did mine for the first time in 28 years. the entire system was full of goo (but worked fine). i decided to drain the entire system. removed, disassembled and cleaned the m/c completely (used emory cloth on the corroded spots in the bottom of the m/c at the piston seal points) with old brake fluid (wipe all parts with lint free rags). use compressed air to blow all the brake cylinders clear of fluid (don't worry about hurtin' the p-valve) from the bottom up. do this with the m/c off and stick a couple of empty Gatorade bottles on the end of the m/c lines. Beware of spaltter (don't get brake fluid on your car like ''I" almost did). reassemble clean m/c, installed new pads and fresh new fluid per manual. i used a vac kit, but the reservoir cap kept splitting (junk) but it got fluid thru the system okay. it was fine for the first two days. then "Oh oh", my light came on and didn't go out either. but i trust the system and drove around for two weeks back and forth to work with the brake fail light on. paranoia set in and i got my son to help me 'buddy' bleed them again on a saturday (took about two hours). i did get 'soft pedal' when starting out in the a.m. once or twice, but firm at the bottom. as the car acclerated the power boost seem to work okay and no 'soft pedal' at speed (just at idle sometimes). been driving like this since mid June. just yesterday (August 13) the light went out by itself! Yippee! and today it goes out by itself after driving a little ways or pushing down on the pedal gently (it seems to be fixing itself). there's hope .... don't give up. have trust and patience. cars never had this stuff on them when i was a kid and we believed it was okay then too. good luck.