No rear brake pressure problem.

[SkidmarkSS]

After troubleshooting today i discovered that i have no brake fluid coming from the back of the proportioning valve that regulates the rear brakes,the car(87ss IN THE SIG)had the disc/drum prop before and now has a disc/disc set up.the master cylinder is the stocker so maybe i need a disc/disc master to get more fluid to the rear,maybe one with a bigger bore than 15/16 also? There is plenty of pressure from the fronts to the point where the brakes locked up a couple of times because maybe it is getting too much. What do you think?

 

[prairiehotrodder]

There is a safety valve in the prop valve that stops fluid flow if there is a big leak such as when you took your brakes off to replace them with the disc setup. This is what you need to do: Unhook the rubber brake hose at the rearend. Unhook the steel line at the master that feeds the rear brakes (don't get that part wrong, I forget which one it is) Then using a blow gun, blow air from the back. That should move the safety valve forward. Then hook up the master and let it gravity bleed for a couple hours. Then bleed it normally with a helper.
Brian

 

[LS6 Tommy]

Although Prariehotrodder outlined a viable combo valve reset procedure, that's probably not what you need unless the brake warning light is on. A disc/drum master doesn't move enough fluid volume nor does it produce enough pressure for rear disc brakes, so you'll need the proper master, too. Generally, stock disc/disc masters are 1 1/8" bore.

If the brake warning light is on, you may need to reset the safety in the comb valve. Many of them are spring loaded & will reset once the pressure loss in the system has been repaired. Sometimes (rarely) they stick. LIGHTLY tapping on the combo valve by the warning light switch with a SMALL soft hammer may jar it loose. If the valve stuck once, it may stick again & I'd replace it. Since yours is new, I'm assuming it's not spring loaded & sticking. You'll need to reset it manually. I prefer this method:

If you're not getting fluid at on end of the car, open the bleeders on the opposite end, slam the pedal to the floor HARD & hold it there while someone quickly closes the bleeders. You don't introduce any air that way. You may have to repeat this until the brake warning light goes out. Keep an eye on master cylinder fluid level. Then bleed the brakes on the end that didn't originally get fluid until you get a firm pedal.


Tommy