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Brakes

Tiny
SIERRA GUY
  • MEMBER
  • 1997 GMC SIERRA
  • 5.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 100,000 MILES
Brake pedal slowly sinks to floor. Also noticed rear drum brakes sometimes grab when backing up. Could the proportioning valve be the root of my problem? Cannot find any leaks and fluid is full. If I change the master cylinder should I also change valve?
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Monday, July 4th, 2016 AT 10:54 AM

5 Replies

Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,005 POSTS
I'd rule out the P-valve till last, they seldom mess up.

I'm going with the possible "internal leak" (fluid leaking past the plunger/ o-rings in the bore) in the master cylinder

Bench bleeding is a challenge on the bench- I do it on the vehicle (takes 2 folks but works fast!)

This 1st video may show the process that needs to happen/ couple it with the 2nd video (a little cruder video) You'll see how much EZier I think it is.

https://www.youtube.com/watch?v=9bEPrO99B5A

Here's the actual "on vehicle" process

https://www.youtube.com/watch?v=i3Jhbz4mVKw&feature=related

These are videos I found-They ain't mine at all!

Down here is another answer I gave, it may aid you too

https://www.2carpros.com/questions/1980-jeep-cj7-cj-brake-problem

Return with good news!

The Medic
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Monday, July 4th, 2016 AT 11:31 AM
Tiny
SIERRA GUY
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Success, everything is copacetic.
Murphy only reared his ugly head twice.

Thanks for your help, Tom
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Sunday, July 10th, 2016 AT 12:21 PM
Tiny
CJ MEDEVAC
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Just for giggles

Did any of that help? Or did you go another route?

If so, what was most beneficial?

The Medic
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Sunday, July 10th, 2016 AT 2:04 PM
Tiny
SIERRA GUY
  • MEMBER
  • 21 POSTS
Bleeding the master on the truck was a big help since there were two of us. Only took maybe 25-30 strokes. The idiots at autozone were almost no help at all. The bleeder kit consisted of two plugs. Once master was bled did have to bleed all 4 wheels 5 times to get all the air out. Did it in order every time.

Thanks again
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Sunday, July 10th, 2016 AT 4:46 PM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,005 POSTS
So now,

Looks like you owe me lunch!

8 Krystal Burgers and a Coke would probably do it!

LOL!

Glad you got it and I was able to help somewhat,

Send your pals here too, we've got many fellers that know their stuff answering questions!

The Medic
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Sunday, July 10th, 2016 AT 6:05 PM

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