[brakes] Caliper dragging

Bebop

Well-Known Member
Joined
Nov 16, 2019
Location
TN
Ok, I'm going to pick the brains of the forum members...

2002 Silverado 2500HD with a 8.1

2 weeks ago I had to do an emergency stop on the hwy to avoid an idiot merging last mine. Full on panic stop, ABS engage etc... Barely missed him.
When I started moving again, the front axle was shaking like a mofo around 50mph for some reason. It never did so before.

I was 2 miles away from home to I pushed on and when I made it in the driveway I realized the right front brakes were locking up. Thick white smoke, heavy brake smell etc...

I let it cool overnight and the next day I took it for a drive. Came back home after 5 miles, same thing happening again.

On a whim, and since they needed pads and rotors anyway, I shotgun new calipers, pads, rotors and hoses in the front. Same results.

I did plenty of testing so here is what happens : When I press the brakes, the right front caliper locks up. Leave it alone for 45mn/1h and it slowly releases. Press the brakes again and the same thing starts over.

I did unbolt the master-cylinder from the booster, same problem.

The weird thing is, if I put a big screwdriver between the pads and rotor, I can pry the caliper open and everything is fine until I press the brakes again. So they're dragging, preventing me from spining the tire by hand, but not clamping hard enough that I cannot push the pistons back in.

Maybe it's an issue with the pressure relief in the master (???), so I'm going to swap a new master tomorrow, but realistically, I'm out of ideas.

One thing to note, from time to time, I have the ABS light that comes on and off, due to a bad sensor (maybe ?), but I don't think it's ABS related because of the fact that the same problem happens every time I press the pedal. Same thing when the engine is off, ignition off, or on.

Thoughts ?
 
Flexible hose? They are probably 20 yrs old. Cheap and fairly easy to try, and should probably be replaced anyway due to age.
 
Same exact situation on my f350. Person pulls out in front of me and brake issue. I will be watching out for ideas.
 
I have had the same thing hapen to me over the years, it was something different each time.
once it was the hose, the other time it was the brake line it's self.
BOTH times it happened just after doing the same thing you did, slamming the brakes hard, as in as hard as I could to avoid an accident.
My theory was, there was some rust build up, from where anything with a fluid other than water will do, from some moister getting into the line and causing some rust. Hitting the brakes hard, cause it to dislodge and create another blockage. mash the pedal, and fluid is able to get by it, release the pedal, and it prevents the fluid from going back towards the master.
Doubt this helps, but thought I'd share.
BTW, while in my name, I never touched the brakes, or any of it's components, so, not sure how old any of it is.
 
New calipers are probably rebuilt by Jose or HopSing, could still be bad. Glad you replaced the flex lines. were you able to get all of the black gook out of the fluid through bleeding? I think it causes issues. And again with all of the hardware, is it all good and sliding as it should?
I replace GM 2500 and 3500 brakes on my junk regularly.
 
Brand new ACDelco calipers.
Brand new slide pins (properly lubed up), bolts, etc

I did clean most of the old fluid out but I'm sure it wouldn't hurt to bleed them more.
 
Pump the brakes some to get them dragging and then open the bleeder screw. If fluid sprays out and the dragging goes away you know it’s a hydraulic issue. From there you can crack the lines loose at the master to see if it’s the abs pump or the master cylinder.
 
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