1987 Chevy Truck Front brakes sticking

Tiny
ZPGEIB
  • MEMBER
  • 1987 CHEVROLET TRUCK
  • V8
  • 2WD
  • AUTOMATIC
  • 79,000 MILES
I have an 87' Chevy P30 Step van, 350 Auto, The front brakes keep sticking/building pressured. I have to crack/open the bleeders on the front to release the pressure every 10-15 miles (depending on how many times I press the brakes). It has new: master cylinder, metering block, flex lines, calipers, pads, rotors, rear pads, repaired line in the rear. The only original stuff is the hard line from the master cylinder to the front & rear block. I'm afraid I'm going to ruin the rotors. They have already been " cherry red" at least twice. I've taken it back to the shop that put all this stuff on 3 times. They changed the metering block on the second time, changed the master cylinder (again) on the third time. I just drove it home and it did it again
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Wednesday, November 11th, 2009 AT 8:20 PM

5 Replies

Tiny
SERVICE WRITER
  • EXPERT
Multple part replacement can throw a few wrenches into things. But I would do this:


http://www.2carpros.com/forum/automotive_pictures/30961_xvan_1.jpg



http://www.2carpros.com/forum/automotive_pictures/30961_xvan1_1.jpg

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Thursday, November 12th, 2009 AT 5:41 AM
Tiny
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Thanks for your response. But I have a question, how does this affect the front brakes building up pressure?
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Thursday, November 12th, 2009 AT 9:05 AM
Tiny
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  • EXPERT
The height sensitive proportioning valve provides ideal brake balance according to weight at rear axle.

There doesn't seem to be a balance rather a large difference between the front and rear. The imbalance may be diverting pressure to the fronts.

The proportioning section of the valve proportions outlet pressure to the rear brakes after a certain rear input pressure has been reached, preventing rear wheel lock-up. Instead you are having front wheel lock up. Where the lines run into the correct ports on the valve?
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Thursday, November 12th, 2009 AT 11:58 AM
Tiny
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I apparently don't have this "Height Sensing Device". I've crawled under it and there is nothing. Still not sure why it keeps sticking?
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Sunday, November 15th, 2009 AT 8:05 AM
Tiny
SERVICE WRITER
  • EXPERT
It's part of the metering valve.

Are any of the metal lines run close to the exhaust. Possible boiling brake fluid? I assume the brake fluid is fresh.

Since there is a relationship to how many times the pedal is applied, If you were to pump the pedal before it is started, will the caliper then stick or create pressure that is not releasing?

Another thing I would check is movement of the pads in the bracket. Pull a caliper and see if the pads are free.
IF they are too tight, this could happen. I assume a quality brake lube was used.
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Sunday, November 15th, 2009 AT 6:48 PM

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