2000 Chevrolet Silverado brakes dragging, 4 new rotors, 4 sets of pads, new e-brake shoes, new front calipers

Question

I recently replaced myself or had replaced all pads, all rotors, front calipers, rear guide pins and brackets, rear brake shoes, and rear e-brake hardware, as well as the e-brake cable on my 2000 Chevrolet Silverado 1500 4WD (4.8L). After the front work, I noticed a smell and found that the front passenger rotor was getting hot and would eventually start having a bad brake smell if I drove long enough.

After some research, it looked like the primary culprit was thought to be the brake hose (due to possible internal collapse). So I replaced it as well. Still dragging.

I had it brought in for part of the work because I wasn't having any luck removing some seized parts, and I had them look into it, and they said when they drove it, they couldn't get it hotter than the rest. I drove it home last night and it seemed fine, but towards the end of the drive, the pedal seemed to be getting harder. So this morning, I mashed on the pedal a few times before getting too far from home, and by the time I got to work, the pedal was fairly stiff (noticed braking action within about 1/2" - 1" of movement tops, which it's never been that tight before) and the front passenger rotor smelled. I grabbed our heat gun and recorded the following temps (They were probably hotter, but I spent a few minutes after arriving looking for our heat gun before I could measure them):

• Front Passenger: 220 F
• Front Driver: 165 F
• Rear Passenger: 135 F
• Rear Driver: 165 F

This truck has a split front-to-rear hydraulic system. So I have a few ideas and was looking for validation (or dismissal) of these ideas, other ideas, other ways to troubleshoot this, and what I should try first.

• Rear Driver brake hose. Due to the split front-to-rear configuration, if a faulty brake hose can act like a check valve, could it be stopping fluid backflow for this entire line?
• Rear Driver caliper. I can't imagine this would cause the Front Passenger to stick, it would just cause the Rear Driver to not retract and burn up the pads and rotors, but I thought I'd put it down since I haven't replaced it ;-)
• Master Brake Cylinder. Could it be something (debris, faulty check valve) at the master cylinder that is causing this portion of the line not to back-flow?
• Electro-Hydraulic Control Unit (EHCU). Same reasons as Master Brake Cylinder, clogging on one line but not on another.

So any thoughts on this one? This brake work has reminded me that I hate brake work.

Edit: I also replaced the front passenger side caliper on warranty from AutoZone where I bought it because I thought it was defective (due to the dragging). Same issue.

Answer 1

I have seen this behavior with a bad ehcu but is rare, they have an internal valve for each wheel, but it does happen.

Internal collapsed brake hose I have seen many times, also sticking calipers use to be common but I hardly see that anymore since they went back to steel pistons. Steel piston calipers can do this but requires a lot of internal corrosion on the piston to make it happen.

After a test drive and you suspect wheel drag, open the caliper bleeder screw on the wheel that is dragging, if fluid squirts out (back pressure), then you have a blockage upstream from the caliper, if no fluid back pressure is present then suspect a bad caliper.

If you do get a squirt (back pressure) at the caliper, repeat this process, test drive etc, each time moving upstream toward the master cylinder, by loosening a fitting to see if you get back pressure. When you find a place where no back pressure is found then it is between there and the last place you got back pressure.

It is rare a Master Cylinder is the cause, but I have seen this a few times myself, some brake boosters have adjustable push pins, if they are adjusted too far out they will hold the master cylinder piston in just enough to block the return port, and it does not take much inward piston travel to do this. You don't usually see these adjustable pins on American trucks, I only remember this being the cause on foreign cars. If it is the master cylinder it will cause all wheels to drag, so I don't think the M/C is the cause in your case.

Answer 2

EDIT: While I do believe I still had bad calipers as it did make a noticeable difference in performance, a few weeks later I ended up seeing the same issue AGAIN. This time I took it to my trusted brake shop, and they ended up diagnosing a bad ABS unit. Could this have been the problem all along and just changing the calipers released enough pressure that I got along with softer-than-necessary brakes for a few weeks? Possibly. Hard to say. Just wanted to add more info here in case anyone discovers this in the future with the same issue. Check (or have your shop check) your ABS unit too.

Original Answer: Well, @paulster2 gets it right again. 2 bad calipers in a row. Got a different caliper from another parts store and put it on and it is working great today.

My ultimate diagnostic test in determining that it had to be a faulty caliper was this: Once I drove the truck around and got the brake nice and tight, I jacked it up, pulled the wheel off, and opened the bleeder valve. a small amount of fluid came up but not very much and the caliper was still tight. I had read about this troubleshooting technique but I kept trying to figure out things further up in the brake system. But ultimately I realized that any pressure further up in the line, no matter the source, could be relieved at the bleeder. So I did the bleeder test and even pulled the caliper back and forth with the rotor loose and it never released (but the new slide pins allowed the caliper to move beautifully). I even took off the supply line with the intention of replacing the caliper and then tried it again (so nothing was connected to it) and still frozen. Bad caliper.

Lesson 1: Buy RockAuto or Napa. Lesson 2: Don't trust the probabilities. Trust the facts :-)