Hi All!

I'm new to this site, so please be easy on me if I don't do something right.

Anyway, I have a 2007 GMC Sierra Crew Cab Pick-up, and for the past three weeks now, I've been experiencing drag sticking or drag. My first mechanic has replaced the brake pads (twice), the calipers, the front brake hoses, and the rotors (twice). I have ran the truck without the ABS fuse in, and have had the entire braking system checked by two different mechanics. Each mechanic tells me the braking system checks out to be good with no codes thrown. The ABS, the master cylinder, and the power booster all check out to fine, and nobody seems to be able to determine as to why my brakes stick/drag or lock up for no known reason.

Yesterday, they locked that tight that the mechanic and I, working together, could not spin the wheel. In just three weeks, I had to replace the brake pads and rotors twice, and should probably replace the rotors again due to high heat warpage. The only thing I haven't done yet was change out the brake fluid. The first mechanic had trouble getting the brake lines to bleed when he replaced the calipers and rotors the first time, and I'm told that he ran a quart of fluid through the lines until they all bled, so I'm thinking the brake fluid can't be contaminated, but thought I'd do it again just to make sure. Any opinions on this idea?

Both mechanics are fed up, and have both told me to take the truck to a GM dealer mechanic, as neither of them know what else to do. Could this be a GM malfunction? Maybe a cause for a recall? I read on here somewhere before that others were having the same problems as I.

Any and all advice or solutions would e greatly appreciated, as I can't be putting more money out for this. I have well over $600.00 invested in new parts, some I paid for twice, and still don't have an answer for the cause of the problem.

Thanks Guys,
Troy

You check the pads to see if they slide free. Some times all it is is the pads have casting sharp edges that need filed and some caliper grease.

The brakes don't stick or drag all of the time. It seems to only happen when the outside temperature is above 85 degrees. Would the sharp edges still be a factor? The calipers were gone over after they were installed. The first mechanic blew out any brake dust and greased the calipers, as that was already considered to being the problem.

When they decide to stick or drag, it starts out very slightly. The farther I drive, the harder they stick or drag. They will eventually return to normal, but not for long. At times, I really have to give the truck gas in order to pull out from a dead stop. The other day I used almost a 1/4 tank of gas just to go 7 miles. There are no modifications to the truck, and it is completely stock or factory. According to the computer, I was right around 16.4 miles to the gallon, so to go through a 1/4 tank in just 7 miles, should give you some idea as to how bad these brakes are dragging.

How long will my aluminum wheels hold up with the amount of heat coming off of the brakes? This is my main concern. Last thing I want to do is hit a pot hole or manhole cover with hot wheels, and take a chance on ruining the front wheels. I won't let my wife drive the truck with the kids, just because I don't trust the brakes. With the amount of heat coming off these wheels, I fear the rims will bend or the tire will blow. Most times the brake pedal is normal, but when the brakes start to stick, the pedal can be very sensitive. Sometimes you'll have to push very hard, especially when driving for a long distance, while other times you don't have to push at all, due to the brakes grabbing. The truck will pretty much stop itself.

My wife is disappointed the most, as she likes to drive the truck. I too am disappointed, as this is probably the best truck I've ever owned.

Well, when that wheel was locked up or hard to move, the first thing I would have done was open the bleeder....if the wheel then spun easily, that meant there was a pressure build up, and you go in that direction...

But if it still was hard to turn, and the sliders were ok, and there was no pad interference, then I would get a new caliper....sounds like piston is hanging up....

After the truck was up on the lift, and we found that we couldn't turn the front wheels by hand, the mechanic lowered the truck and hooked up the computer and did a brake bleed. He repeated this check three times, and everything checked out good. I thought a pressure build up was the problem too, and that is why I asked about possible brake fluid contamination. Yes/No?

As for the calipers, they are both new and have been replaced just early last week. If indeed it is the calipers that are causing the problem, what would be causing both of them to lock up at the same time? You have to understand, this isn't just one side or the other when they lock up, it'* both sides at the same time. They both release at the same time too, whenever things start to cool down.

If BOTH are locking at the same time, it does seem to be an ABS problem....

Naturally a TSB search should be done....it certainly sounds like an ABS problem...I tend to doubt it'* a sensor problem, more like a module or programming problem...

I'm betting it'* a sticky dump valve in the ABS. I would look for a replacement at the salvage yard because new the ABS modulator can be very spendy.

So even if I have the ABS fuse disconnected, the ABS still works? The brakes stick with the ABS fuse in, and also if the ABS fuse is pulled. I pulled the fuse to see if the brakes still stick, in which they do, so I figured the problem couldn't be the ABS. Besides, the mechanic checked the ABS system and all checked out OK.

If the mechanical valve is sticking in the modulator it won't matter if the ABS fuse is in or not. That'* why I'm thinking you need to replace the whole modulator. The only other thing it could be is the bore is sticking in the master cylinder causing pressure to build up. You need to find out if the pressure build up is before or after the ABS modulator. If you crack the lines at the master cylinder and the pressure releases you need a master cylinder. If you still have the wheel locked and you crack the line at the wheels and the pressure releases it'* probably the ABS assy.