armonica

The 3500 has around 40K miles. It's not used much. I had it out recently and after I had to stop a bit harder than normal I realized there was a hell of a drag to it. Like I had a bobcat on a trailer behind it. The truck would come to a stop by itself. So I lifted the front wheels. They were free. I lifted the rear wheels, they were tough to move. So I took the calipers off and looked at the shoes. They had rusted and were stuck good to the metal liner. So I popped them out, did the wire brush, grease bit. Worked fine. For a while. Then it did it again many miles from home. I let the truck sit while I worked on a job. When I drove it home, no problem.

Figured I'd just spend the $40 and buy a new set of bendix shoes, get a new metal liner for them to go into and the right grease for it. I put that all on today. I noticed that one piston on the right rear caliper was significantly harder to push back than the others. Most of them pushed right back in, no problem. I went to take it for a ride. Even though the calipers slid over the brakes with no problem, they're binding. I took a short drive. When I parked they were HOT. I used water to cool them down.

Maybe I'm missing something? Maybe I need to bleed them some more? Secret setting I need to reset?

Any help greatly appreciated.

tech2

Maybe a seized caliper. what did you used to push the piston back?
measure the rotor temp with a IR heat gun to confirm if the problem is one brake or all. Any outliers are a concern.
make sure you remove all rust from the caliper bracket b4 you install the clips. replacing brakes is more involved than putting on pads and rotors. The pins must be lubricated and the brackets clean or the pads and caliper don'ts move properly.

armonica

I bought a handy dandy caliper piston pusher. It has a whole bunch of tops to deal with the various makes. I used a smooth one. It has a pin twist type handle to push it back. I recently did a brake fluid exchange after this had all started to become a problem. In this case I simply released the nipple while turning the screw so I wouldn't overfill the brake reservoir in the front of the truck. Not that I've ever done that (whistle). I cleaned the calipers with a wire brush. The pins are nice and free as well as greased. While I think the rear right was probably binding worse, both rear brakes were clearly very hot. You could smell it and feel it if you brought your hand near it. Both boiled the water good when I sprayed it with a garden hose.

That's why I'm scratching my head. I've done many disk brakes over the decades. My Cadillac had a parking brake caliper seizure one time. That was obvious and stuck good. This one is almost as if the master cylinder isn't releasing it properly or something. Maybe it's ABS? Air in the system? When I pressed the brake it sort of sounded like the ABS was growling a bit. I don't remember if it did that before.

Thanks

William Kisselstein

air in it wouldn't let it apply fully. If there's no lights on the pressure in the system should be correct. I'd consider changing the caliper in question.

Triaged

Sounds like you need new calipers.

If you crack the bleeder is there pressure in the caliper or is the piston sticking? Sounds like the piston sticking but it is possible for rubber brake hoses to fail internally turning into a one way valve that would hold pressure. When doing the calipers new hoses might not be a bad idea.

Finally you mentioned the ABS ... I have heard you need a good scan tool to bleed the brakes.

What year is your van?

armonica

It's a 2016 Express 3500. I was worried that I need a scan tool to do part of this.

armonica

I did some debugging. It's not that the brake line is holding it. On both sides it's the bottom piston that's the problem. If I push it back using a screw type reset then it works fine. I can apply the brake and it'll come out. I can push it back by my thumbs with some effort. If I put it on the brake and use the brake peddle lightly it's fine. Only if I apply some real pressure to it does it lock up. Now it's in big trouble. If I put the van in neutral I can't move it by myself. Not a chance. You'll need to pry the caliper off the pads. If I apply some brake pressure to push the bottom piston out first then it'll go in a lot easier.

I think something happened to the O ring inside. I don't have access to the equipment or parts to rebuild it. Maybe at some point in the van's life it got too hot. It used to be an Enterprise rent a van. I'll replace the calipers and call it a day.

Thanks!

tech2

that is the problem with some caliper piston tools...they can push back everything. the proper tool....won't push a seized piston back.
the one you have is best used for calipers that have the ebrake build into the calipers.

armonica

Turns out it was the calipers. I replaced them both with autozone reman and oh what a difference!

Triaged

Glad you got it working! I did some more looking and it seems that you only need the scan tool to bleed if you get air into the ABS module.