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In need of a brake expert!!! Anyone?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Jersey, Aug 1, 2002.

  1. Jersey

    Jersey 1/2 ton status

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    Hope someone can help me out on this. My right rear brake is locking up on me when i hit the brakes slightly harder than normal and the truck is pulling to the right, obviously! Anyway, I rebuilt both axles about 6 months ago (D44, 14FF), bearings, brakes, seals, calipers, rotos/drums turned, bled them and all was fine. About three months ago while pulling a trailer, my left rear seal, i'm assuming, heated up and leaked all over the brakes, which like now, made the truck pull to the right. Took it apart, replaced the seal, which looked fine, and the soaked brakes and wala, no more pulling. About 2 weeks ago, same senerio, pulling trailer, started to pull to the right figured "damn, wish i figured out the first time" but at least i knew (or thought i knew) what it was. Last week, pulled the wheel, axle, drum, to find the brake shoes wet again so i change them again, put it all back together and damn, still pulling and locking right rear wheel when pressing hard. Bled the brakes (pump method, gravity method) several times, no help. Then i loosened the right rear adjuster real loose and tightened the left rear REAR tight just to see what would happen...barely any brakes and when i layed on them....pulled to the right! So, to say the least, i'm at my wits end. It has rear ABS which i wouldn't think would be any different with bleeding, but possibly? There is what looks like 2 porportining valves under the hood next to the master cylinder. 2 lines out of the MC go to the first prop valve, one line comes out, goes to a splitter and to the front brakes. Other one comes out of prop valve to, what i'm assuming is another prop valve and has something to do with the ABS, then comes out of there to my rear brakes. Maybe something wrong with the ABS circuit? can i disconnect it easily somehow to try it without? Of all the times i've ever did brakes, the fronts would always lock up first unless i really layed on them to get all 4 skidding. This right rear is locking up first and making the truck pull hard if put a good amount of pressure on them. I'm stumped and stubborn because i dont want to take it to someone else. I dont like anyone else working on my truck but it might be coming to that...so....PLEASE HELP. If you have any suggestions, they'd be appreciated. Sorry this is so long winded, just wanted to explain the full story.

    - Jersey
     
  2. 79Beast

    79Beast 1/2 ton status

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    IN my experience, one wheel locking up usually indicates a bad wheel cylinder. Also, what type of fluid is soaking the shoes, is it gear dope or brake fluid?
     
  3. Jersey

    Jersey 1/2 ton status

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    gear dope. Looked like grease the first time i changed the brakes out. Thinking about it again, i don't think it could be the abs circuit or the proportioning valves because it would effect both rear wheels, not just one, right? hmm...this sucks. Thanks for the post.

    - Jersey
     
  4. Khi5in

    Khi5in Registered Member

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    that valve you are describing sounds like a height sensor. Don't ask me why they call it that but it does regulate equal pressure like a prop valve but it is only on abs vehicles. see if the pessure coming from this is equal at both ends. if not it may be that valve causing your problem. just a thought but might help.
     
  5. Khi5in

    Khi5in Registered Member

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    I know this might sound dumb but is it possible you got an e brake stuck on? happened to me once.
     
  6. DieselDan

    DieselDan 1/2 ton status

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    Another "dumb" thing to check. Alot of brake shoe sets have a lead shoe and a trail shoe with more friction material on one (lead?) than the other. You wouldn't have both leads on one side and trails on the opposite would ya? /forums/images/icons/blush.gif
     
  7. andrey busurgin

    andrey busurgin Registered Member

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    It happens only when go with the trailer? /forums/images/icons/frown.gif
     
  8. Blue85

    Blue85 Troll Premium Member

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    Why not just put gear lube in the right side brake? /forums/images/icons/laugh.gif

    I think that only one main brake line goes to the rear in your setup, so both back brakes should get the same pressure. If they pull differently, it has to be in the brakes (wheel cylinders, adjustment, shoes, grease, etc.).

    Any bad pulling I have ever had was due to the front brakes.
     
  9. Jersey

    Jersey 1/2 ton status

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    first off, thanks for all the suggestions. The answer is somewhere in here!!! haha.

    Khi5in - Thanks for the info on the valve. Figured it had to be particular to ABS vehicles somehow. But as Blue85 said, if there's pressure coming out of it, which there is, and going down that one line to where it hits the splitter above the 14ff, then it really shouldn't have anything to do with the prop valve or height sensor. Also checked the Ebrake, all ok. thanks

    DieselDan - yeah, they do have a lead shoe (thinner) and a trail shoe (thicker) - or maybe that's reversed but i did make sure they were correct before i put it all back together. Amazing how you double-check everything 1000 times before you wrap a 14FF back together. Not as easy as other trucks to get to the brakes! Thanks.

    Andrey - It pulls all the time now when you step on the pedal a little harder than normal and obviously more with a trailer because of the weight on the rear wheels but it seems the geal oil blows by the seal (happened 2 out of 2 times) when i'm towing. Figured the extra stress is heating up the axle and creating the blow-by. why? i don't know. checked the fluid - ok. checked the vent - ok. i replaced the seal the first time, which looked fine, and the soaked brakes on that side and everything was great with the braking for a few months before i towed my boat with it the second time. The second time i didn't repalce the seal because again, it looked fine. who knows.

    Blue85 - ha, ya know, i bet that darn thing would STILL lock up under pressure with lube on the brakes!! You are right with the one brake line so it really HAS to be something else then the valves/sensor. Why would it be locking up? I've never had a brake locking up unless i had them adjusted too tight. Usually they'd be too soft after a new brake install. This is what i'm now thinking....front brake lines swollen a little bit due to being 12 years old - creating a little back pressure. Left rear brake has got lube on it again, somehow, someway. So the only brake that IS working good, with less backpressure than the fronts and dry, is the right rear, the one that's locking up. How's that? A stretch, huh? yeah, i thought the same. What gets me is that when i bleed all 4, they all bleed good and strong. Thanks man for the suggestions. appreciate it.

    - Jersey
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    Actually, the brake pads work TOO good with oil on them. Act normal when they are cold, but after 5 minutes (or less) of use, they will lock up the tire solid with very little pedal movement. Makes you look like a fool stopping for a light with one wheel sliding/screeching/smoking.


    Don't ask how I know : )
     
  11. Jersey

    Jersey 1/2 ton status

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    really? hmm.. maybe there's oil on the right now? Strange because the first time this happened it was pulling hard to the right, i took off the left rear wheel/drum and found the soaked shoes. after i replaced them, it stopped pulling to the right, until i towed again. Guess she doesn't like towing /forums/images/icons/crazy.gif Thanks for the info.

    - Jersey
     
  12. m j

    m j 1/2 ton status

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    is there a pivot bolt in that setup on/near the park brake lever?
    is it siezed or well lubed free moving?
    I hate drum brakes and would just throw the works into the trash and go disc from one of the members on here.
     
  13. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    My 14 bolt has a 90 weight lubed brake on the right side...it never locks up at all.

    I have heard that if the brakes are not adjusted tight enough they will grab and lock though. The trailing shoe makes contact and then pivots hard because it has room too if that makes any sense.

    Rene
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    I put a new wheel bearing/axle seal in a 10 bolt car axle (7.5") and noticed shortly afterwards the seal leaked. I pulled it all apart, replaced the bearing/seal (it was a repair bearing) and inspected/cleaned the brakes and drum.

    Put it all back together, and drove it. Sure enough, as soon as the brakes got warm, THAT wheel only locked up. 35mph, 25mph, whatever, it locked up. I replaced the shoes on both sides, and problem was gone.
     
  15. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Well I never cleaned or repaired mine yet so it does nothing /forums/images/icons/crazy.gif With welded spiders the drivers side does all the braking for the rear and it really doesn't pull at all unless I really hammer the brakes. with 90 weight still on the shoes it just polishes the drum a little.../forums/images/icons/smile.gif

    Rene
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    I kinda figured this was the reason. And since this is from the Internet, it has to be true:

    "Grabbing brakes are most often caused by contaminated linings. Grease or oil can cause the linings to swell at spots and on drum brake systems these swollen spots contact the drum too quickly and can cause the brakes to grab."
     
  17. Blue85

    Blue85 Troll Premium Member

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    Yeah, tRusty has your answer. Put a spool in the differential and then different brakes left to right won't matter. /forums/images/icons/smile.gif
     

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