Rear brake pressure regulator valve, Brake repair Options

[DamonsCarrera]

The brake pedal on my 914-6 is very spongy, even after repeated bleeding with a pressure bleeder. I isolated the problem to the brake-proportioning valve or pressure regulator. I cannot seem to get the brakes properly bled with this valve in the system.

I've read other posts by some here and it seems this valve is a source of some debate . Is there some trick to bleeding the brakes with it? Do I need to bleed the brakes the old-fashioned way, have someone push on the brake pedal?

[toolguy]

Air seeping past the bleeder threads on the calipers. . . this was when i tried using a Mity-Vac. . no matter how many times I bled them, I keep getting air bubbles. . because the Vac was sucking air past the thread as well a fluid from the caliper. .

Next thing is to make sure your partner understands what "Pump it up" and "Hold the pedal" means until you get the bleeder tightened. . that's been the cause of many arguments when you get the wife to help .

Removing the compensating valve isn't a good idea. . It's purpose is to keep the back brakes from locking up under very hard braking . . As you apply hard brakes, the cars weight is transferred to the front and the rear end get's light. . without the valve, the rears tend to lock up and the resulting fishtailing is unpredictable especially at high speed. .

The amount of rear braking can be adjusted by the external allen bolt, which controls inside spring preset pressure. . It's preset at the factory and not a normal adjustment without measuring inside hydraulic pressure. The compensator factory preset is different from Six's and Four's.