Jump to content

Dragging brakes

Purplejchild

By Purplejchild
in Ask A GM Technician

 Share

Recommended Posts

Purplejchild Enthusiast

Purplejchild

Posted
Posted

I have a 2011 Chevrolet Silverado 2500hd 4x4. It has developed a dragging brake issue.  I have changed all 4 calipers,  brake pads,all brake hoses,master cylinder, and hydro boost, flushed with new fluid. It shows no check engine or Abs lights or codes. I can drive it between 10 to 20 miles and you can start to feel the brakes applying till it locks up. Then I get out and pop the brake line and relieve  the pressure  then we're  fine for awhile till it starts all over again. I've  taken a temperature gun to the calipers when its locking up and the front can be up to 180 degrees and the back up to 150 degrees, or it can be the back hotter then the front. I've  taken it to a dealer and they have scanned it and with no codes they are saying it has to be a mechanical issue, but I have changed all the mechanicals except the hard brake lines. I am starting to think it's the Abs module or pump,  but with no lights or codes I hate to put another 1000in this gamble. Any advice or help would be much appreciated.  Thank you!

Purplejchild Enthusiast

Purplejchild

Posted
  • Author
Posted (edited)

It's only locked up once and was the rear. Once I feel the brakes start dragging,  I pull over and open the bleeder valve on the caliper  and it's  ready to go.  As your going down the road you can feel  the breaks start dragging. 

Edited by Purplejchild
tlaw91 Enthusiast

tlaw91

Posted
Posted

You had contaminated fluid prob from hydro boost going bad leaked into the master.
Anyways when oil gets into the brake fluid it causes this issue.
So when you started replacing parts you didn’t replace them all at the same time so the master cylinder got contaminated again.
Replace master cylinder again, but be SURE you’ve flushed out everything before putting another one in.


Sent from my iPhone using Tapatalk

davester Senior Enthusiast

davester

Posted
Posted

If the fluid was contaminated enough to cause something to fail, such as a seal to swell up or something like that, just flushing in new fluid (which you indicated you had already done) isn't going to fix those bits, you have to find and replace them.

tlaw91 Enthusiast

tlaw91

Posted
Posted
If the fluid was contaminated enough to cause something to fail, such as a seal to swell up or something like that, just flushing in new fluid (which you indicated you had already done) isn't going to fix those bits, you have to find and replace them.

^ what he said
Replace the master again.


Sent from my iPhone using Tapatalk
Purplejchild Enthusiast

Purplejchild

Posted
  • Author
Posted

Let me ask you this.  The hydro boost wasn't leaking when I replaced it. It was dry inside. The reason  I replaced it was, after driving  the truck about 15 miles and the brakes  just start to drag the brake paddle would  might  a high pitch squeak then after I release  the pressure in the brake line the squeak would go away but then redevelop when the brakes start to drag again.  Now after replacing they just start to drag with no squeaking. 

Purplejchild Enthusiast

Purplejchild

Posted
  • Author
Posted

One guy was telling me he thinks it might be the abs module.  Since it not effecting the same wheel it bounces around one time it might be the back dragging  and the next time it's the front. He recommends pulling all 3 abs fuses and driving around and slowly putting in each one back in till I can narrow it down to the right system. Any thoughts on this or do you think it's still in the master cylinder?

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Typically if oil gets in the master cylinder (most common way for oil to get in master is someone topping the brake fluid up and using the wrong fluid) the seal on the cap will swell up.  BTW, avoid topping off the brake fluid reservoir, there is more than enough brake fluid in the master to account for pad wear.  Its not like it gets used up.

 

You say you open a bleeder, which one, and is it always the same one?  There are two circuits in the brake system, if you only open one bleeder, and it is always the same one, then you have narrowed it down to just half the brake system. 

 

Since you have already replaced the master cylinder, that should have taken care of a plugged compensating port in the master.  This port allows brake fluid to "leak" back into the master cylinder as the fluid expands when driving on the highway (long instances of no brake application).  If that port gets blocked, pressure will build up in the disc brake system, eventually applying the brakes enough to stop the vehicle.  That port can also get blocked by an incorrectly adjusted brake pin that goes between the brake pedal and master cylinder.  But, if the master was not removed, or no one had touched the brakes prior to this happening the first time, it will not be that pin misadjusted.  Touching the brake pedal while driving(aka riding the brakes) will also block that port.

 

Personally I have no idea if the ABS can cause any of this, I "retired" before ABS became common.

Purplejchild Enthusiast

Purplejchild

Posted
  • Author
Posted

I usually open the drivers front and when I do the pressure is relieved and the truck rolls foward a bit

tlaw91 Enthusiast

tlaw91

Posted
Posted

Contaminated hydroboost systems aren’t common but they do happen.
I’ve also heard abs modules staying ‘on’ and holding brakes.
Also,
Double check pushrod length/adjustment, make sure there’s free play in the pedal, if the rod is too long, or adjusted too far in, it’ll hold the pistons inside the master beyond the compensator ports and never let pressure bleed off after applying brakes

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Latest Articles

  • Posts

    • Chuck FB
      Joke Thread

      By Chuck FB · Posted

    • Ryanwehr14
      2018 Sierra 1500 Transfer Case Leak

      By Ryanwehr14 · Posted

      Pretty much zero rust on the truck, the frame is super clean. Non-snowy area of California for its whole life. They didn't mention JB weld specifically, just a silicone style seal. 
    • newdude
      2012 Sierra 1500 AC issues

      By newdude · Posted

      Needs a manifold gauge hooked up and the pressures read.   If you don't have one, time to take it to a shop and have it diagnosed.  
    • newdude
      2018 Sierra 1500 Transfer Case Leak

      By newdude · Posted

      How rusty is the truck?     The transfer cases on these are an aluminum case.  If its anything like the rear diffs on the 2015-2022 Chevy Trax, those will corrode bad to the point it will push fluid through the housing via corrosion porosity or a crack from age/stress.    We have seen folks over tighten the drain and fill plugs on these transfer cases and crack them that way as well.    So I'd say its a 50/50 shot on re-sealing the case.  If all of the surfaces are good and its not badly corroded, they probably can re-seal it.  GM uses RTV to seal the case halves.   If they mention JB Weld, the issue is the case.  Be it a crack or corrosion.  JB Weld "might" hold if they clean EVERYTHING very well and drain the fluid out of the case and clean the crack and then seal it.      
    • Ryanwehr14
      2018 Sierra 1500 Transfer Case Leak

      By Ryanwehr14 · Posted

      A while back, my truck (2018 GMC Sierra 1500 5.3) went in for an o2 sensor and routine service. The tech identified that my rear output seal on my transfer case was leaking, and recommended I have them replace it. At the time I didn't think anything of it, and had them do the repair. Less than a month later, I noticed that the recently repaired seal was leaking again. I called the shop that did the repair and they warrantied the repair and replaced the same seal again. A few months later, I noticed that once again the same seal leak had come back. It wasn't a great time to bring it in and I ended up just living with it for 6 months or so, noticing small (smaller than a baseball) size oil stains below the truck when it would sit for a while, as well as oil spray on the frame (to the point where it actually took the underbody coating off in that one spot). Finally got around to brining it in again, but this time I took it to a dealership service center since I am in a different part of the state for school. They identified the same output seal leaks and recommended they replace them. They also said there was no scoring on the inside of the transfer case, so it didn't need to be replaced. They chalked up the original repair failures to non oem seals and a job that wasn't done correctly. Now they called and said the seals are holding after driving/sitting for a while, but they found a very small leak in the middle, that they recommended they seal with some kind of silicone/jb weld (not sure what they are using). I haven't picked up the truck yet, but I have been reluctant about this whole repair process because I feel like they are just fixing the same thing that keeps coming back, and I am concerned there could be another root cause for the seal failing. Has anybody else experienced anything like this, or have any ideas on other things that could be the root cause?

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...