sticking front disc brakes

17 years ago

93 Dakota. RWABS 3.9 liter auto.

Had to slam on my brakes today to not t-bone a celphone idiot who pulled out in front of me. Now the truck pulls hard to the right when I apply the brakes, and there is a smell of something getting hot. Right front wheel quite a bit hotter than left after driving in town a short distance. I'm figuring the calipers are sticking, not pulling the pads away from the rotor...I'm not a mechanic, but given time can usually deduce the problem. I've done disc/drum brake jobs before, so not concerned about capability to fix it. I'm just hoping for thoughts from others who have dealt with this before I start digging into things.

Thanks for any advice/thoughts you may offer.

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Comments (4)

jemdandy
17 years ago
The caliper may be jammed on the pins, or the piston jammed in its bore.. For everything to work right, both the caliper and piston must slide freely. Since this was an emergency application of the brakes, there's no telling how much pressure was applied. The piston may be jammed in the bore and not releasing.

Corrosion on the pins can cause a sticking caliper.

The piston does not have a return spring. It moves back solely by what little return is provided by the elastomer boot and the brake pad can rub gently on the rotor. Another source is a restriction in the brake line that is holding up pressure, for example, a porportioning valve jammed closed.

Its time to take the brake apart and inspect. If you do take it apart, may as well replace the pads unless the pads are relatively new. However, overheated pads can be dangerous because these are prone to loosing chunks of friction material.
john_g
17 years ago
Hi Jem.

What returns the piston to it's rest position after releasing the brakes is actually the square cut bore to piston seal. Under normal braking, the piston moves only a few thousandths of an inch so the seal stretches with the piston movement. If sufficient wear has occurred, the seal will allow the piston to slip through taking up the clearance, but still remaining in it's stretched shape during application.

For the O.P. We use an infrared thermometer to test for brakes that are over working, as well as to see if any are not working at all. Pulling to one side can be caused by that side grabbing, which can many times be pad/rotor contamination. one typical source of pad contamination is tie-rod, or ball joint grease. Since it is pulling to the right, it could be that the LH side does not work at all. We also have to consider front end component wear or looseness. You have some work to do in order to find the problem.
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OK, gents... I completely took off the caliper assy from the car because the piston would not retract even if I opened up the bleeder nut. I thought this would be a 30-minute job but it already took 2 evenings of my time. I'm just looking at the caliper sitting on my desk now while typing this. My experience level? Maybe a typical Saturday menchanic. I've done a few motor R&R on motorcycles and small boats, replaced pistons on lawn mowers, water pump/alternator on cars, etc. I don't have a larger enough C-clamp, so I used a carpenters adjustable wooden clamp. But still no go. The caliper piston is stuck hard in the extended position. Any idea what's going on or what to do? Thanks in advance.
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jemdandy
17 years ago
I had a similar incident with a full size sedan 20 yrs ago - had to hit the brakes and pull down fast from highway speed, and afterward, the car began to pull right upon applying the brakes. The fix required a brake job on the front disc brakes. The brake pads were 'cooked' and one of those had broken up and half of the pad had spit out.
kalining
17 years ago
Too bad you didn't get a licence number. (maybe you did ?).
Anyway when that happends to us, up here. we turn in their
number to the police and they get a visit and could be charged. That means any traffic violation that the other driver could have been hurt in as in yourself. If the driver is charged god help them. Up here the police charge them. Our courts charge them, the D.M.V. charge them, and the insurance company finishes them off. I think this is the only place on the planet you get charged 4 times for the same crime. If you have one at fault accident your drivers licence goes from $34.00 to $200.00. Your basic car
insurance could go from $1000.00 to $2000.00 for the next 5 years. I'll bet your brake caliper is worn and got twisted sideways on the pins. Jammed. Normally it is the piston that seizes on the return from rust build up behind the dust seal caused by water contaminated brake fluid that
hasn't been changed since 1993.

sticking front disc brakes

Comments (4)

jemdandy

john_g

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