Hi All,

Have an '86 Crown Vic 302 with 260,000 miles runs great. Yesterday replaced the brake master cylinder and rebuilt rear brake cylinders. During brakeline bleeding found that front wheels bled fine and brakes work fine. Rear wheels would not bleed. Even pulling a vacumn on rear cylinder bleed ports pulled no fluid down from master cylinder. Traced problem down to what looks like a fancy 4-way valve with a 2-wire electrical connection, downstream from the master cylinder. Determined that fluid was going to this valve, but not getting past it.

1) What is this valve, and what is it supposed to do?

2) Any idea why this valve is not passing fluid to the rear brakes?

3) Is there some simple way to get this valve to resume passing fluid to the rear brakes?

Thanks,
George

On vehicles equipped with front disc and rear drum brakes, a proportioning valve is an important part of the system. It is installed in the hydraulic line to the rear brakes. Its function is to maintain the correct proportion between line pressures to the front and rear brakes. No attempt at adjustment of this valve should be made, as adjustment is preset and tampering will result in uneven braking action.

I believe that you need to remove the lines to the master cylinder and just bleed the master first. Sometimes there an air lock at the master that need to be bleed. Then open the front brake valve and let it drain the fluid. After you install the line back to the master, start bleed the brakes from the rear right, the brake furthest to the master cylinder.