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Rear brake prob

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MA87K5, Mar 3, 2003.

  1. MA87K5

    MA87K5 1/2 ton status

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    My father has a 3/4 ton 84 Chevy pickup with 1/2 ton axles. (The guy before him did that stupid swap.) The rear wheel cylinders and lines were replaced and there is still no brakes in the back. Plenty of pressure for the front though. Brakes were bled. I think that the booster is bad. My reason is the I had my father pump the brakes then hold them, and I loosened the line at the master cylinder and it released the fluid like it did in the back. I did both lines on the master. I did the same thing to my Blazer and the fluid shot out. Am I correct? Has anyone else had this problem? Thanks
     
  2. 76SILVERADO

    76SILVERADO Registered Member

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    proportioning vavle.....
     
  3. sunshineoffroad

    sunshineoffroad Registered Member

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    My first guess is also proportioning valve, but... When I did my rear disc swap on mine, I also put in a new Master Cyl. The bleeders they used to give with the hoses was replaced with two threaded plugs. Problem being is that they did not bleed the master cyilinder good enough, and it had air. Be sure the master cylinder is bled! I did not get any fluid movement to the rear of mine until I bled the master cyl with the bleeder screws with the hoses that gpo into the master cyl. Just another option.
     
  4. MA87K5

    MA87K5 1/2 ton status

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    If it was the proportioning valve then the fluid would of shot out at the master cylinder like it did on my Truck. But the fluid seems not to have the correct amount of pressure. Maybe the new master cylinder is bad. The guy who owned it before said he put a new one on. I think that it is either the master cylinder or the power booster that is bad.
     
  5. 79Beast

    79Beast 1/2 ton status

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    I would guess that the rear is out of adjustment. The shoes need to be adjusted so that they are very close to the drums. The wheel cylinders only have so much travel so it the drums are out of spec or the shoes are out of adjustment, they will work poorly or not at all.
     
  6. MA87K5

    MA87K5 1/2 ton status

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    The rear brakes are adjusted correctly. The e-brake is fine. I don't think it is the prop valve nor the rear brakes are not adjusted correctly. This is a problem with the fluid pressure. I by-passed the prop valve by checking the pressure at the master cylinder. The pressure at the master and the wheel cylinders are the same. Would a bad master cylinder cause this? Or would the power booster? Thank you for the help so far. I do kind of wish that the people who reply do understand the post they reply to. Then I wouldn't have to explain in even more detail. I don't mean to offend anyone by any means or tick you off. If I have done so then I apologize.
     
  7. MA87K5

    MA87K5 1/2 ton status

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    Well it turned out to be the prop valve. You guys were right.
     

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