Dragging brakes

[turbo_bu]

I have a 2004 K2500 with around 105,000 miles on it. A couple years ago my rear calipers would not release. So much so that it wore the inner pads down to nothing. I replaced those with reman calipers and that seemed to fix the problem. I have also already put in new brake lines and hoses. Now I have been noticing that both my front and rear brakes seem to be dragging. After driving say 10 miles with little to any braking, I get out and try to touch the brake rotor and it is very hot. Before when I originally replaced the rear calipers, I was checking my rotor temps after driving. You could put your hand on the rotor and it might be slightly warm. These are HOT.

I hate to throw parts at it, but could the master be causing this? Maybe the hydro boost? I had thoughts of just replacing the front calipers, but the fact that the rears are getting hot has me confused.

 

[2004LB7]

clean and grease the guide pins

 

[turbo_bu]

In the past I have used anti seize to grease the pins. Is that ok, or should I use something else?

 

[kaylabryn]

Synthetic Brake caliper grease, I think I got mine at Napa. Seems to last longer. This is what I use currently.

CRC® Brake Caliper Synthetic Grease, 8 oz. tub

A specially developed synthetic grease with a high-tech formula for use in disc & drum brake systems. High temperature grease is plastic & rubber safe. Use on metal to metal contact points and sliding surfaces. Resists moisture and will not washout.

www.crcindustries.com

 

[Bdsankey]

I've always used high temp anti-seize/brake caliper grease as it has a much higher temperature range than anti-seize and is developed to work with the plastic guides/boots usually found on caliper slide pins.

Even on new calipers we re-grease them as they seem to have been dry lately coming from the manufacturers.

 

[turbo_bu]

I finally had a few hours today to dig into my brakes. Pulled all four corners off and lubricated everything with high temp synthetic brake caliper grease. On the fronts, still original GM, I used a c clamp and exercised the pistons 3 times to make sure they moved in and out without any issue. They were both fine. After putting everything back together, I took it for a drive. Unfortunately, all four rotors were HOT.

Any recommendations on what next to check or work on? I am considering that the hydro boost might be sticking. Could it be the master cylinder is sticking? When I exercised the front calipers I was having to pump the brake pedal a couple times to get the pistons to extend. I would think that this should help with getting both the hydro boost and master cylinder moving.

 

[Ron Nielson]

When was the last time you exchanged the brake fluid? Have you tested the brake fluid for moisture percentage? Brake fluid readily combines with humidity from the air. If humidity-laden brake fluid gets hot, it turns to steam and expands, and pushes out the brake calipers. And then your brakes are applied, but all of them, not just your rear brakes.

 

[2004LB7]

also, I think old rubber brake lines can do something similar by internally collapsing and keeping the pistons from fully returning. not sure in your case since it seems to effect all four. so I would lean towards the master cylinder or ABS module. or as Ron said, moisture in the fluid

 

[turbo_bu]

Fluid was replaced when I did brake lines a couple years ago. I also replaced about half the fluid when I swapped rear calipers last year. All the brake lines and hoses were done at the same time, so I don't think it is the hoses. I used new GM hoses when I replaced everything.

I agree either master or ABS, just trying to troubleshoot it a little better. Or if this is common, trying to go after the usual suspect first.

 

[Ron Nielson]

I think there's air in the system. That's the only thing I can think of that would affect all 4 corners.

You have:
New Calipers - bleeders at the top (?)
New Brake Pads
New Brake lines and Hoses - No leaks (?)
Lubed slide pins - calipers slide easily (?)
Partial new brake fluid
Low mileage truck

If I'm in Phoenix and it's 115*, I wouldn't be touching the rotors after braking, but if I were in Aspen at 60, MAYbe I would.

I'm guessing that since you replaced your brake lines, you live in salt country? If so, what condition are the caliper mounting brackets in? Rust where the pads touch?

You could pull the ABS fuse and see if any difference.

That's all my guesses.

 

[turbo_bu]

Ron, thanks for your continued help. Yes, bleeders are at the top, no leaks, and calipers slide easily. I know touching the rotors is a hack way of checking things, but it was how I checked my rears when my calipers were sticking. Granted, those were so bad that I could smell the brakes when I got home. No need to touch the rotors, they were very hot. But after replacing the calipers, you could touch the rotors and they were only slightly warm. Same for the fronts, warm, not HOT.

I am curious as to unplugging the ABS. I had to do this before when I lost a wheel speed sensor. Truck would still stop, but dinged at you when you first started it. One of the repair manual talks about having to replace the brake valve in the ABS, but I am not sure if unplugging this helps to prove it or not. Do you know what it is doing having it unplugged?

 

[juddski88]

Ron, thanks for your continued help. Yes, bleeders are at the top, no leaks, and calipers slide easily. I know touching the rotors is a hack way of checking things, but it was how I checked my rears when my calipers were sticking. Granted, those were so bad that I could smell the brakes when I got home. No need to touch the rotors, they were very hot. But after replacing the calipers, you could touch the rotors and they were only slightly warm. Same for the fronts, warm, not HOT.

I am curious as to unplugging the ABS. I had to do this before when I lost a wheel speed sensor. Truck would still stop, but dinged at you when you first started it. One of the repair manual talks about having to replace the brake valve in the ABS, but I am not sure if unplugging this helps to prove it or not. Do you know what it is doing having it unplugged?

Master cylinder seal leak is my guess. I've even had a less than 1 yr old new gm master cylinder start leaking air into it. You can test for this by replacing the lines with threaded plugs and applying brake pedal. It should not move.

Unplugging the abs controller will not tell you if the abs valve body is leaking or if a valve has hung a bit. It will only remove the very rare chance that a solenoid is shorted and pulling on the Pintle of the valve

 

[Ron Nielson]

Unplugging the ABS connector would allow you to understand if the ABS unit was causing your problem. My guess is that it isn't, but you never know, and unplugging is quick, easy, and free.

 

[juddski88]

Unplugging the ABS connector would allow you to understand if the ABS unit was causing your problem. My guess is that it isn't, but you never know, and unplugging is quick, easy, and free.

There's 2 parts to the abs "unit"...the logic controller/solenoids and the motor/valve body. They are physically separate and the only possible way the electric part of it can be a problem in this case, is if a solenoid is energized enough to pull a pintle to a valve and close off that circuit...

 

[Ron Nielson]

Agree, but the easiest, quickest way to test is to remove the connection. If you have lots of knowledge of the inner workings of the EBCM, you have expertise that many others just don't have and you could make valid judgments about the situation.

 

[juddski88]

My point is that your statement that unplugging the ABS unit will allow him to determine if it was causing the issue, is false. As I said before, the valves themselves can mechanically stick, or the fittings can leak, or the motor seal can leak. Unplugging the connectors tells him almost nothing.

 

[Ron Nielson]

You've said that all before and I agreed with your statement.

 

[turbo_bu]

Played with the hydro boost and master last night. Jacked up the front end and rolled around one of the tires. Yes, dragging. Unbolted the master from hydro boost, still dragging. Nothing obviously wrong with the hydro boost. Couldn't really actuate the master with it in chassis, but no obvious leakage. Took off the caliper and pushed the pistons back, reassembled the caliper and pads everything was good. Put master back on hydro boost. Still good. Had wife push on the brakes a couple of times while I was rolling the rotor around. It seemed to be ok. Less drag than what I started with.

Going to check the rears tonight. Last night was hot enough. Got to love over 100 heat indexes!

 

[Dean E]

My point is that your statement that unplugging the ABS unit will allow him to determine if it was causing the issue, is false. As I said before, the valves themselves can mechanically stick, or the fittings can leak, or the motor seal can leak. Unplugging the connectors tells him almost nothing.

I think one thing that might help. With the brakes hot and dragging, jack up one wheel and put a diagnostic tool on the truck and turn on the ABS bleeding. Then see if the brake still drags. Dean

 

[juddski88]

You don't need to jack up a wheel to do it. You can also activate the same process by jamming the brakes on a grassy surface or a gravel road if you do not have a good diag tool