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Binding brakes by calipers?? Advice please

Discussion in 'Brakes' started by Realism, May 4, 2016.

  1. Realism

    Realism Well-Known Member

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    Having issues with my front brakes binding and I think it is my calipers, but I don’t understand why or how.

    Back story and progression: 2004 GMC Envoy SLT 125K miles

    October last year I started getting brake drag and turned out it was my parking brake on drivers rear that was refusing to release. Couldn’t get it to release no matter what I did and since I have never used it, I cut the cable to that side (noticed further up the covering was damaged so needed replaced anyways). During this time the Drivers front was starting to not let up, so I took it apart and inspected. Piston in the caliper was frozen. Went and bought a new caliper set for both fronts and decided to change the Brake fluid as well (was almost pitch black – previous shop never really changed it).

    Transferred old slide pins to the new calipers, lubricated, installed. Bled brakes in order to flush out the old stuff. Everything was doing fine.

    March of this year the drivers front brake started to get tight to where the caliper wasn’t fully releasing. (Recent divorce so money was tight), couldn’t quite figure it out after checking it out again and put it on my to do list when I had the funds. Currently the passenger front brake has started binding and not wanting to release either and its heating up the rotors as of yesterday. You can hear the pads contacting with the rotors the entire time driving and they started to squeal on drivers side, but there isn’t any metal contact from the pad. And lots of brake dust.

    Today I went through the motions to troubleshoot. My brake pedal has felt a little stiff for a long while now, but it passes all the brake booster checks. Pulled the ABS fuse and went around the block, it felt a little bit better, but it could have been just wishful wanting. Put the fuse back in.

    Pulled the tires off and neither caliper was movable. Rotors could be turned with some moderate effort. I cracked the bleeder valve on both to see if a bad flex line could be keeping pressure on the calipers, but no luck. Never heard of both calipers going bad at the same time. Pulled the calipers off to inspect them. They both took more pressure than they should have to press back in with a C-clamp. Sliding pins on passenger side are normal with that little bit of squish to them, but the pins on the drivers side keep sucking themselves back in flush (which way is normal pushing out against caliper or pulling in). What I found interesting was the rubber boots around the pistons, both on drivers side and one on passenger side, appeared to look like they had air puffed up inside them. I found this very strange.

    The calipers are still under warranty I believe and I can take them in, but is there something else that is going on here that could be causing this braking problem?

    driver side.JPG Drivers caliper.JPG drivers slides.JPG Passenger Caliper.JPG Passenger slide.JPG
     
  2. littleblazer

    littleblazer Gold Supporter

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    I have a possible guess? I have an issue where my brake sometimes doesn't grab well. It turned out to be the metal clip/slide for the pad itself. It was slightly deformed and it would prevent proper engagement. Noticeable at stop if you pressed the pedal you heard a creaking like noise. My mechanic actually pointed it out while I was getting tires. He said he's seen the increased pressure plus the lack of full contact kill calipers quick. I guess it's possible that's your problem? How hard is it to move the pads?
     
  3. Realism

    Realism Well-Known Member

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    Now that you mention it, one of the metal clips on passenger side was warped a little on the outside non contact center, likely from the heat buildup. (didnt effect movement, but will get replaced anyways)

    With the calipers off, the pads come off and go back on easy and smooth
     
  4. littleblazer

    littleblazer Gold Supporter

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    Interesting. I got nothing else. I'm sure someone has some input on this. I haven't really dived into brakes on this truck too far.
     
  5. Mounce

    Mounce Silver Supporter

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    Slide pins. Check them for free movement and grease them while you're at it for extra measure.
     
  6. Realism

    Realism Well-Known Member

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    both sides have free movement and they are greased up. Only difference between two sides is that the passenger side is out just a little (you can push it down and it will pop itself back out a little) and the drivers side you can pull them out easy, but the boot sucks them back in.
    With the caliper pistons pushed back the caliper has freedom of movement on the slide.

    Its those boots I dont understand. The piston boots just dont look normal to me, like there is air pockets behind them or something.
     
  7. Mooseman

    Mooseman Moderator

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    Did you try prying the boots off the pistons to see if there is fluid in there?
     
  8. Sparky

    Sparky Moderator

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    I'd check for fluid built up behind the boots (could indicate a weeping piston seal).
    Also depending on age it may not hurt to go ahead and replace the brake hoses as well.

    My 02 started doing the same thing on the driver side front, but since the poor truck is now dead and getting parted out I never actually had a chance or reason to dig into it and fix it.
     
  9. Realism

    Realism Well-Known Member

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    No I didnt. Always thought prying the boots off would cause damage and make them not operate well. I will check them, but would both sides have fluid buildup like that at the same time?
    Wouldnt opening the bleeder on the calipers have released any build up of fluid and caused them to retract so they could move, or does pockets of fluid in the boot not return

    Could the ABS system have anything to do with the problem?
     
  10. Mooseman

    Mooseman Moderator

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    I doubt the ABS would do this. Just prying the boot lip off the piston won't do anything except allow you to confirm if the piston seals are leaking or not. They are dust boots, not a fluid seal. If opening the bleeder spurts out fluid and the piston retracts, there is blockage somewhere, probably a rubber line, that is doing this.

    What brand were the rebuilt calipers? And I guess these were just the calipers with no brackets and pins since you had to transfer the pins over. It may be worth it to get full sets with the brackets so you have all new hardware. But you did say that your current pins/sliders were good.
     
  11. Realism

    Realism Well-Known Member

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  12. Mooseman

    Mooseman Moderator

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    Pistons don't really retract a whole lot on their own, just a little to get the pads off the rotor, which is not a lot. Try compressing the pistons back into the caliper, the same as if replacing the pads. They should easily go back in with a c-clamp or compression tool.
     
  13. Realism

    Realism Well-Known Member

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    Fully compressing till they are flush or just enough to slip it back on?
     
  14. Mooseman

    Mooseman Moderator

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    I'd say all the way as a true test.
     
  15. Realism

    Realism Well-Known Member

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    Okay, so I compressed them all the way in. While I was at it, I cleaned the glaze off the rotors, scrubbed the brake clips and ears of brakes, and reapplied some brake grease on the ears to help things slide a little better. Put it all back together and pumped the brakes to seat the pistons.
    End result: Sounds much worse than it did before. You can really hear the pads contacting the rotor, moreso on the passenger side. Went three blocks and temped the rotors. Rears were at 98, but driver front was 109 and passenger front was 118. 2 minutes driving.

    *note: the pistons went back in with moderate c-clamp pressure. Havent dont brakes all that often to know how easy it should be.
     
  16. Sparky

    Sparky Moderator

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    Did they compress easy enough or take a fair bit of force?

    If they compressed without too much fuss I'd lean towards hoses.
     
  17. Realism

    Realism Well-Known Member

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    got me right during the edit :smile: didnt take the heave ho to get them in, but it wasnt too terrible I guess.
     
  18. Sparky

    Sparky Moderator

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    Sounds about normal then.
     
  19. Realism

    Realism Well-Known Member

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    So you thinking that both my flex lines failed? I've started considering that as well. It's just that since the calipers didnt release when i cracked the bleeder, that would point towards the caliper. the fluid didnt come out fast (I did have a bleeder hose attached). Could there be just enough of a blockage going up the line that I can compress the calipers, but too much of a blockage to allow them to return on their own after braking? ugh, both lines at the same time. gotta love it
     
  20. littleblazer

    littleblazer Gold Supporter

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    Is it full on scraping or is it more so a sporadic scrape like once a revolution?
     
  21. Realism

    Realism Well-Known Member

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    Full on.
    I think they are the factory rotors. even have a nice little lip from wear.
    I plan on ordering and replacing the whole brake assembly on both sides; calipers, mounts, pads, rotors and flex lines. It's just waiting on the shipping time while still having places to go. was hoping to find at minimum a temp fix - graduation ceremony required to go to an hour away saturday
     
  22. gpking

    gpking Well-Known Member

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    I thought I had an issue with my calipers not releasing (I about tore my hair out diagnosing the noise), but it turns out it was just normal heat from the brakes (stop n' go interstate traffic) causing the rotors to expand ever so slightly and scrape a bent abutment clip as well as the rusted-out dust shields:
    (Approx. speed, 25mph)

    (The rattling is from a shot rear endlink, btw)

    Cutting off all four of the dust shields, grinding rust buildup off of the outside edge of the rotor, and adjusting the bent abutment clip fixed my noise.

    Don't rule out actual brake issues in your case, but any strange brake noise could very well be caused by the dust shields.
     
  23. Realism

    Realism Well-Known Member

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    heh heh shot rear end links. The plague of the Envoy line :crackup:
    Thanks for the audio there. The rubbing is much louder though. No contact on shields, but you are right about that rust build up on the lip of rotor. I would agree with it being normal heat if it was uniform throughout, but glazing and the temps after three blocks...
    You did inspire an idea i think I will try. Going to take a sharpie and paints some lines across the rotors and see if there is one spot that is getting more contact.

    Going to start with Sparky's post. Figure I will walk my backside downtown to the auto parts store and at least pick up some flex lines and see if any changes. Work from least expensive in this case right
     
  24. Sparky

    Sparky Moderator

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    True, and given age/miles it can't hurt anyway.
     
  25. Realism

    Realism Well-Known Member

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    Managed to get a hold of flex lines and passenger right caliper. Started pouring down before I got a chance to fully get things ship shape and test, but I did get the two flex hoses on and bled. I think you were right sparky, the old lines I could barely blow through. Going to test it tomorrow without replacing the caliper and see how she handles. BTW compressing the piston on that side all the way flush was harder than the other side even with bleeder open.
     
    Last edited: May 6, 2016
  26. Realism

    Realism Well-Known Member

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    Verdict is that the brakes appear to be doing better. There is still a bit of rubbing that I am hearing, but once I replace the pads and rotors maybe that will go away.
    While I was down there test driving I did notice that my A arm bushing are in need of replacement. One fun project into another right :smile:
     
  27. Mooseman

    Mooseman Moderator

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    A little rubbing is normal as there is no way for the pads to completely move away from the rotor. As long as the pads are not being pushed against the rotor, it's all good.
     

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