PM question

[jooset]

Just changed brake components, and bled brakes 3 times before finally getting it right (brakes "feel" good now). Did a test drive for about 10 minutes and all checked good. Today I was out for a little longer drive and after 15 minutes, I could hear -hissing- from the PM when foot not on pedal. When braking, no noise. When off the brake....hissing. Perhaps it was the PM running - but it was more than 20 seconds. Didn't used to do this before the brake upgrade - hate to think I screwed up a good component when I did my upgrade.

Same symptoms on the drive to work and home. Doesn't start until about 10 minutes into the drive. Brakes feel fine with and without the noise.

Any ideas?
Thanks.

 

[gofstbuick]

What color is the brake fluid? black? What have you done so far? Instal a new PM unit? If you installed a used unit, it may be the power piston check valve sticking. If that hissing or humming sound you're hearing is the PM motor, then the motor will be hot to the touch (don't touch it for long or you'll get burned). If it is the motor, get your PM fixed ASAP or you'll burn the motor up. Have you tried bleeding the PM part of the master cylinder? Turn ignition on, until PM motor stops, turn ignition off and then loosen the hose below the accumulator, until brake fluid flows, then tighten it up (CAUTION!!!!!!: DO NOT COMPLETELY REMOVE HOSE, ACCUMULATOR OR PRESSURE SWITCH IF THE SYSTEM IS STILL PRESSURIZED. WE ARE TALKING ABOUT 700PSI OF PRESSURE). So you can loosen the hose, but don't completely remove it.

 

[Quigs]

Maybe you should check for leaks in the A or B ports. Or maybe your control valve is leaking.