2001 Silverado 1500 rear brake issue - calipers not releasing

[wazzabie]

What could be causing both of my rear disk brakes on a 2001 silverado to lockup? I replaced both rear the calipers and brake hoses. I lubed the slide pins and they moved freely.

To bleed the brake I had an assistant hold down the brake pedal. I then opened the bleeder valve to allow air to escape and then closed. Then the assistant released the brake. I bleed the brakes with tire off.

 

[myhichevy4x4]

I had a similar problem on my dad's 2001 2500 rear disk brakes after I did new pads and rotors. They were very touchy and getting hot. After some research I found others had suggested to make sure the pads fit freely in the caliper. I filed some of the paint off the metal pad backing "ears" where they fit in the calipers so they could move freely and not bind. That seemed to fix it.

Also make sure if you replaced the rotors you checked the adjustment of the parking brake as that is what was causing the rear rotors to get hot on his truck they were adjusted too tight due to the new rotor.

Not sure if that will fix yours but it fixed his.

 

[diesel4me]

If both calipers stay locked after applying the brakes,it could be the rubber rear hose(s)--I have seen a few old original ones decide to become a one way check valve after a bleeding session..
The inner lining gets all gooey or separates, and the bleeding process can make it come loose and clog up inside,and only let pressure from the master cylinder go to the calipers or wheel cylinders,but not "release" when you let off the pedal..you can open the bleeder screw and see if that releases the caliper--if so,then the hose is probably at fault..

If just one side stays locked,it could be the pads as suggested,the E-brake,or the caliper itself might be sticking...just because its new or rebuilt doesn't mean it isn't defective...

 

[wazzabie]

I'm thinking the problem may be a bad Master cylinder.

 

[diesel4me]

Maybe,but I doubt it--the typical failure of a master cylinder after a bleeding session,which does happen sometimes, is the piston seals inside it can get torn or damaged when you push the pedal all the way down,which puts the piston in it further down in the bore than it normally travels,where it could be rusty or has dirt built up in the bore..then you'll have difficulty getting enough pressure to get the system bled and air can sneak back into the lines again when the pedal is released..

There are check valves in the master cylinder ports on some vehicles, where the brake lines screw in,those could possibly fail,but it would be pretty rare,especially if it was working normally before the bleeding..not sure if yours would have those with rear disc brakes or not..

 

[Blue85]

Check that it's not the parking brake, too. The little shoes can wander off their intended location - especially on the driver's side where the clip design is "upside down".

So why did you replace the calipers? Because the old ones were also locking/dragging? I'm not a fan of the metal-on-metal slide pin design, but with new calipers and (I assume) new pins that should be OK right now. The inner pad also has to slide inside the caliper, so make sure that is free to move. I like to use that black synthetic caliper grease on the inside pad and the pins. Sometimes the new metal pad clips fit strange and take some tweaking before everything moves OK.

Sometimes they seem to drag but after driving a bit they free up. Of course there are limits on how hot you should let it get.

 

[wazzabie]

Check that it's not the parking brake, too. The little shoes can wander off their intended location - especially on the driver's side where the clip design is "upside down".

So why did you replace the calipers? Because the old ones were also locking/dragging? I'm not a fan of the metal-on-metal slide pin design, but with new calipers and (I assume) new pins that should be OK right now. The inner pad also has to slide inside the caliper, so make sure that is free to move. I like to use that black synthetic caliper grease on the inside pad and the pins. Sometimes the new metal pad clips fit strange and take some tweaking before everything moves OK.

Sometimes they seem to drag but after driving a bit they free up. Of course there are limits on how hot you should let it get.

When I took the original rear calipers off they both would not release. It was very difficult pushing the cylinder back into the bore. So I just got new calipers and replaced the brake hose at the same time. With the new calipers I'm still getting the issue with the rear brakes not releasing. It was so tight the wheels were hot to the touch.

I'm not sure what else to replace. Perhaps the proportion valve?

 

[Chevy305]

A word of advice for bleeding: when you do it without the wheel on, take 2 lugs and tighten the rotor to the hub. If you don't it allows the rotor to float off the hub and not get proper actuation of the caliper sometimes leaving air trapped. Give it a shot.

As far as the calipers sticking, with both sticking I'd look upstream at the ABS module.

 

[Blue85]

When I took the original rear calipers off they both would not release. It was very difficult pushing the cylinder back into the bore. So I just got new calipers and replaced the brake hose at the same time. With the new calipers I'm still getting the issue with the rear brakes not releasing. It was so tight the wheels were hot to the touch.

I'm not sure what else to replace. Perhaps the proportion valve?

This is interesting because I've had the same problem with mine. After rebuilding the calipers it all seemed fine, but I've always felt like there is a little more drag than there should have to be. I would hate to think you have a problem with the ABS module.

To test the hoses, it seems like you just need to bleed, then push the piston back with a clamp, to push fluid back to the reservoir. If fluid goes both ways, the path should be clear. If the piston is hard to push in, you could crack the bleeder to see if that makes it easier. Then you know if the piston is hung up or there is a restriction somewhere.

 

[rampage]

To test the hoses, it seems like you just need to bleed, then push the piston back with a clamp, to push fluid back to the reservoir.

I don't have ABS and have never worked on them so I don't know how true this is, but I've heard that you're not suppose to push the piston in or you can damage something in the ABS system. You're suppose to crack the bleeder and then push the piston in, then top the system off and bleed it. Again, don't know how true that is. Maybe someone can confirm or bust this myth.