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Rear bleeding issue

Discussion in 'Brakes' started by Darkpassnger, Apr 6, 2016.

  1. Darkpassnger

    Darkpassnger Member

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    Had to replace the 1/4 inch line from the abs module to the rear splitter. After doing this had to bleed them, problem is after trying to bleed the rear brakes several times i'm only getting a few drops(sometimes none at all) out of both rear bleeders but all kinds of pressure/fluid from both front bleeders. I tried a mityvac and got the same result.....no leaks anywhere but i cannot get the rears to bleed....any help would be greatly appreciated! I did research and some say the abs module has air in it and that is why the rear will not bleed and needs an expensive scan tool to cycle the abs to get the air out. Driving and trying to get the abs to kick on by hitting the brake hard ...blocking up truck and free rolling the tires and applying the brakes etc.... anyone have this problem before and found the fix?
     
  2. Mooseman

    Mooseman Moderator

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    Have you tried removing the bleeders to be sure they are clear? I have seen bleeders so plugged that they prevented fluid from coming out even at full pressure.
     
  3. MAY03LT

    MAY03LT Well-Known Member

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    Some peeps have said that smashing on the brakes while on loose gravel has freed up their abs module. I've tried it a few times just to see for myself if it was true but never could get it to work. I always had to go back with a fancy scan tool and do it. Even though it didn't work for me, I think it's worth trying considering the alternative isn't going to be nearly as cheap.
     
  4. Darkpassnger

    Darkpassnger Member

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    yes I took them completely out and blew air thru them
     
  5. Darkpassnger

    Darkpassnger Member

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    Yeah worth a try.......Do you think a pressure bleeder may help any? Seen vids of some ppl making them from a sprayer ? Also do you think its safe to assume that it isn't the mc as it has lots of pressure at front brake bleeders? also thx for both replies
     
  6. Mooseman

    Mooseman Moderator

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    Maybe a pressure bleeder might work. Have you tried opening the bleeder and pushing the piston in with a C-clamp? Then close the bleeder and re-extendd the piston and repeat. Another member had a similar issue and this seemed to have fixed it.
     
  7. MAY03LT

    MAY03LT Well-Known Member

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    You could disconnect the rear input line to the abs unit and see if fluid is going into the unit. I wouldn't rule out the MC but based on my experience with blown out lines in gm trucks I would think it's not the issue. 99/100 times it just needs the bleed procedure done.
     
  8. Darkpassnger

    Darkpassnger Member

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    I have the rear all apart at the moment as I needed to replace backing plates(also bought new brakes and rotors) when i did take it apart the piston pushed in easy enough using a flat screwdriver and prying between the brake pad and rotor(which i wasnt worried about damage as i bought new) but how would i re-extend the piston in that method you suggested? At this point i'll try anything :smile:

    Thanks...ill try that too....cant hurt ....that's for sure:smile:
     
    Last edited by a moderator: Apr 7, 2016
  9. Darkpassnger

    Darkpassnger Member

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    I wonder if there was a way of running the abs motor by using a 12v source and unplugging the harness and using jumper wire to simulate the motor to work? or maybe im way off base?
     
  10. Wooluf1952

    Wooluf1952 Well-Known Member

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    Push down on the brake pedal?
     
  11. Darkpassnger

    Darkpassnger Member

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    That would probably work if I had brake pressure :smile:
     
    jsheahawk likes this.
  12. Darkpassnger

    Darkpassnger Member

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    Just an update.......I tried the rear piston method where I loosened the bleeder pushed in piston...tightened bleeder then pulled the piston back out (did this with a pair of vise grips on the end of the piston.....only about 1/4 inch to grab before the rubber, but it did do it..... pulled it back out and repeated the procedure).

    This did push fluid out of the bleeder and some air ....however after doing this method on the right rear then left rear about 3 or 4 times each , I went back to pump the brake pedal 4-5 times hold and open bleeder method. Problem is when I tried the brake pumping method i get fluid only on the first try then goes back to very little fluid coming out.......i'm stumped as there are no leaks anywhere.

    Any ideas?
     
  13. Mooseman

    Mooseman Moderator

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    Could very well be the master cylinder. Not much else left.
     
    MRRSM likes this.
  14. MRRSM

    MRRSM Gold Supporter

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    Last edited: Jul 1, 2016
  15. Darkpassnger

    Darkpassnger Member

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    Would a pressure bleeder have the same result in the end as taking it off and bench bleeding it? Also is it common to have loads of pressure in the front and very little in the rear if it is indeed air trapped in the MC?
    Thx for all the replies, very helpful.
     
  16. MRRSM

    MRRSM Gold Supporter

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    Last edited: Jul 1, 2016
    Mooseman likes this.
  17. Darkpassnger

    Darkpassnger Member

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    Thx for info....I just got the rear end back together and will now focus on brakes...the rear are working some now from the piston method but i'll try the bench bleed and see what happens...thx again , very informative forum!
     
    MRRSM likes this.

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