Brakes lock by themselves after 5 MPH

1994 GMC C1500
150,000 MILES • 5.7L • V8 • 2WD • AUTOMATIC
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CRYPTOKING
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The truck will drive normally at speeds below 8 MPH. But anything above that and the truck will brake and pull hard to the left. Once the gas pedal is released and the truck slows to 8 MPH, everything resumes normal until the speed reaches above 10 MPH. There are no check engine lights nor are there any codes indicated.
Jul 22, 2021 at 10:41 AM
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JACOBANDNICKOLAS
  • ✓ASE Certified Mechanic
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Hi,

Has anything recently been done to the brakes? Do you hear any sounds when this happens?

Since it pulls hard to the left, either the left front brake is sticking or hanging up, or the right side isn't, working.

Now I realize this happens without applying the brakes, so my first suspect is there is something loose or improperly installed on the left front, or it could even be related to the power brake assist.

I need to know a couple of things. First, has anything recently been done to the brakes? Is this a C1500 truck or suburban? Do you know if the power brake assist is a vacuum assist, or is it hydraulic (hydro-boost)?

Let me know.

Joe
Jul 22, 2021 at 7:36 PM
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CRYPTOKING
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No brake work has been done and the vehicle has vacuum assist not hydro boost.
Jul 23, 2021 at 3:47 AM
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JACOBANDNICKOLAS
  • ✓ASE Certified Mechanic
  • 110,194 POSTS
  • ASE Certified Mechanic
It sounds like the left brake caliper is dragging and locking up to an extent. If there was a problem further up in the system, it wouldn't be affecting what sounds like only one wheel.


I would suggest lifting the left front to see if there is evidence of the brake pads dragging. See if it turns easily and let me know what you find.

Also, make sure there is no play in steering components or evidence of anything touching, rubbing, hitting, or having excessive play that could cause something to move and cause the drag.

Take care,

Joe

Jul 23, 2021 at 6:33 PM
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