Front Brakes Locking Up

Cdouglas · August 14, 2022

Without warning, the front brakes on my 2016 Silverado 1500 LXT crew cab decided to lock up. Took it to my mechanic, replaced the front calipers and pads, had it a couple days and it did it again. Took it back, replaced the flex noses and ABS brain/pump. Drove fine until I was in the wilderness of Canada. when it decided to do it all over again. Left me stranded in Canada for two weeks. We ended up trailering it home. This occurs with no pedal input; just happens. Every mechanic that has looked at it wants to start putting on parts until they hope they have "fixed" it. Is there an electronic connection between the computers and the brakes that could be causing this?

asilverblazer · August 15, 2022

"Left me stranded in Canada for two weeks. We ended up trailering it home."

One wheel or both lock up?

Do they stay locked up?

When/how do they unlock?

2wd or 4wd?

Cdouglas · August 15, 2022

Both lock up, right dominant.

Sometime they release completely, sometimes partially.

I have stamped on the pedal or pulled over to let them cool. Results from both methods are mixed (see above).

4wd.

asilverblazer · August 16, 2022

Is the ABS pump active/running when this happens?

Could the rear brakes be engaged too but masked by the front brakes?

Engine vacuum leaking to the atmosphere side of the booster, would cause the brakes to engage without pedal input, not sure if that is possible though.

Open the bleeder valves when they are locked up to relieve pressure.

Pull the ABS fuse to rule out any ABS issues causing it.

Doesn't sound like a problem with the brakes themselves at least past the ABS pump and valve body.

rlcole321 · August 16, 2022

Yes, disabling the ABS will remove the "Electronic" control, of course all kind of lights will come on, but ignore it for this test.

Cdouglas · August 16, 2022

The ABS pump and controller has been replaced. We pulled the ABS fuse and it still happened. It may be possible that the rear brakes engage, but there have been no indication (heat, smoke) that we get from the fronts.

newdude · August 16, 2022

I'd be suspect of the booster. First couple years of production there were some of the 14-18 body style that engine oil would get into the vacuum lines from the vacuum pump and contaminate the booster. Typically it would cause low or no brake assist rather than complete lockup, but it could be possible.

Has the vacuum pump ever been replaced on it?

Cdouglas · August 16, 2022

No.

asilverblazer · August 16, 2022

3 hours ago, newdude said:

I'd be suspect of the booster. First couple years of production there were some of the 14-18 body style that engine oil would get into the vacuum lines from the vacuum pump and contaminate the booster. Typically it would cause low or no brake assist rather than complete lockup, but it could be possible.

Has the vacuum pump ever been replaced on it?

I was thinking along the same lines, but not familiar enough to know how a failure in that component would result in the brakes applying themselves. I lean more towards the booster not sealing up like it should (maybe contaminated by a failed vacuum pump).

If you pull the vacuum line off the booster and the brakes release at least we're in the right ball park.

The vacuum pump to my knowledge is always running, I don't recall ever seeing a clutch on it, seems to me it is either creating vacuum or not - it SHOULD be creating vacuum at all times (the problem would be present at all times too).

I suppose one could try to pop the belt off the vacuum pump to rule it out of the equation.