Front brakes dragging/ locking
05-07-2021, 06:44 PM
#1
TECH Enthusiast
Thread Starter
Front brakes dragging/ locking First, this isn't for an F-Body, but a GMC Sierra.
This website has some of the best tech minds around, so I came here with my problem... Plus, it DOES have an LS engine...
I have an '07 Sierra Classic, 1500, 2WD, and the front brakes will not stop dragging/ locking.
No stability/ traction control.
Here are all of the parts that have been replaced:
-Front calipers
-Front hoses
-Master cylinder (Two different ones: A new O'Reilly's Brake Best, and a reman Delphi unit, both were correct for the application)
-Brake booster (vacuum booster, for the record)
It will smoke the brake pads after a few minutes of driving, and if you lift a wheel off the ground, you cannot turn it.
BUT: If you loosen the master cylinder from the booster, the front brakes loosen up, and you can turn the wheels again.
THE BRAKE BOOSTER PUSH-ROD IS NOT ADJUSTABLE on this truck, so I'm really at a loss.
Yes, I have disconnected the booster push-rod from the brake pedal when the brakes are locked, and it doesn't do anything.
There are no ABS codes, and the ABS is functional.
Has anyone run into this problem on the GMT800 trucks, or any other car, for that matter?
This website has some of the best tech minds around, so I came here with my problem... Plus, it DOES have an LS engine...
I have an '07 Sierra Classic, 1500, 2WD, and the front brakes will not stop dragging/ locking.
No stability/ traction control.
Here are all of the parts that have been replaced:
-Front calipers
-Front hoses
-Master cylinder (Two different ones: A new O'Reilly's Brake Best, and a reman Delphi unit, both were correct for the application)
-Brake booster (vacuum booster, for the record)
It will smoke the brake pads after a few minutes of driving, and if you lift a wheel off the ground, you cannot turn it.
BUT: If you loosen the master cylinder from the booster, the front brakes loosen up, and you can turn the wheels again.
THE BRAKE BOOSTER PUSH-ROD IS NOT ADJUSTABLE on this truck, so I'm really at a loss.
Yes, I have disconnected the booster push-rod from the brake pedal when the brakes are locked, and it doesn't do anything.
There are no ABS codes, and the ABS is functional.
Has anyone run into this problem on the GMT800 trucks, or any other car, for that matter?
05-07-2021, 08:37 PM
#2
Teching In
I had the same issue I had to grind down the pushrod between master cylinder and brake booster. On a silverado truck tried 2 different master cylinders too. Worked great ever since.
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dixiebandit69 (05-07-2021)
05-07-2021, 10:26 PM
#3
TECH Enthusiast
Thread Starter
I had considered doing the opposite: drilling into the pilot hole in the master cylinder to increase the depth, because the pushrod in the brake booster is recessed and not easy to get to.
What I'd really like to know is how this problem occurred after over 100,000K miles of operation out of the blue.
05-07-2021, 11:47 PM
#4
First, this isn't for an F-Body, but a GMC Sierra.
This website has some of the best tech minds around, so I came here with my problem... Plus, it DOES have an LS engine...
I have an '07 Sierra Classic, 1500, 2WD, and the front brakes will not stop dragging/ locking.
No stability/ traction control.
Here are all of the parts that have been replaced:
-Front calipers
-Front hoses
-Master cylinder (Two different ones: A new O'Reilly's Brake Best, and a reman Delphi unit, both were correct for the application)
-Brake booster (vacuum booster, for the record)
It will smoke the brake pads after a few minutes of driving, and if you lift a wheel off the ground, you cannot turn it.
BUT: If you loosen the master cylinder from the booster, the front brakes loosen up, and you can turn the wheels again.
THE BRAKE BOOSTER PUSH-ROD IS NOT ADJUSTABLE on this truck, so I'm really at a loss.
Yes, I have disconnected the booster push-rod from the brake pedal when the brakes are locked, and it doesn't do anything.
There are no ABS codes, and the ABS is functional.
Has anyone run into this problem on the GMT800 trucks, or any other car, for that matter?
This website has some of the best tech minds around, so I came here with my problem... Plus, it DOES have an LS engine...
I have an '07 Sierra Classic, 1500, 2WD, and the front brakes will not stop dragging/ locking.
No stability/ traction control.
Here are all of the parts that have been replaced:
-Front calipers
-Front hoses
-Master cylinder (Two different ones: A new O'Reilly's Brake Best, and a reman Delphi unit, both were correct for the application)
-Brake booster (vacuum booster, for the record)
It will smoke the brake pads after a few minutes of driving, and if you lift a wheel off the ground, you cannot turn it.
BUT: If you loosen the master cylinder from the booster, the front brakes loosen up, and you can turn the wheels again.
THE BRAKE BOOSTER PUSH-ROD IS NOT ADJUSTABLE on this truck, so I'm really at a loss.
Yes, I have disconnected the booster push-rod from the brake pedal when the brakes are locked, and it doesn't do anything.
There are no ABS codes, and the ABS is functional.
Has anyone run into this problem on the GMT800 trucks, or any other car, for that matter?
05-08-2021, 08:26 AM
#5
TECH Enthusiast
Thread Starter
No. Factory vacuum booster.
05-10-2021, 07:35 PM
#7
TECH Enthusiast
Thread Starter
Okay guys, I ended up drilling out the pilot hole in the master cylinder, and the problem seems to have stopped.
I had both wheels off the ground, and kept drilling and reinstalling the master cylinder until I couldn't feel the wheels dragging anymore.
This isn't how I wanted to fix the problem; I really want to know why it happened in the first place.
Thank you for your suggestions.
I had both wheels off the ground, and kept drilling and reinstalling the master cylinder until I couldn't feel the wheels dragging anymore.
This isn't how I wanted to fix the problem; I really want to know why it happened in the first place.
Thank you for your suggestions.