Urgent-disc brake locked up and im a dummy

Front disc brake locked up smoking and almost caught fire. I know drum brakes but never touched disc brakes. How do I get the pads to unlock and what may cause this? Had xj towed home and its my only DD and gotta work tomorrow. Thanks!

Ken

Various things can cause this, the caliper hanging on the pins, the pads hanging on the rails. Torn boot on the (caliper) piston that gets full of mud and/or rust and siezes. The flexable brake line can seperate (usually inside) and act as a valve, not allowing the pads to retract. Water in the brake fluid will boil, make steam and cause the brakes to sieze. Improper assembly, I've seen guys put the pads in reversed (inner and outer) or two inners on one side and tow outers on the other (though you usually notice very quick, when that happens). Not compressing the piston, before installing the pads, can cause them to heat up and sieze (note, the first braking after assembly, often doen't do much, until the pistons/pad seat to the proper depth).
I got one set of pads, that were so thick, they wouldn't retract all the way (or at all). There was a constant (slight) pressure on the disc, when they heated up they would sieze.

Lol I drowned the heep last week so that likely didnt help. Had new pads a month ago and worked fine till now. How do I get the calipers to release? Any way I can wire them open or something so I can drive (carefully) to work tomorrow? Parts houses are all closed for tonight!

Thanks
Ken

Take two small pry bar type tools, and try to push the inboard pad back. then remove the caliper, squeeze the pad all the way in, reassemble, and see if it does it again

Great will try that and many thanks!

As above, large clamp to push piston back in enough to remove caliper.

BUT

Do not just "see if it happens again", REPLACE the caliper. Sorry...I know its your DD and it sucks, but your life is not worth messing with, it may just decide to lockup again after a hard pedal stomp at highway speed......can you say "Hello Mr. Ditch"? I have had it happen to me....it ain't fun.

JMHO

Rev

I second rev's sentiment. I bought new calipers for the front, they're CHEAP. For my 87 they're about $30 a piece, come with new guide pins all lubed up.
Chances are you're looking at doing caliper, and rotor on that side, and pads on both sides. The caliper is probably warped from that amount of heat and then stopping with the pads engaged.

87manche said:

I second rev's sentiment. I bought new calipers for the front, they're CHEAP. For my 87 they're about $30 a piece, come with new guide pins all lubed up.
Chances are you're looking at doing caliper, and rotor on that side, and pads on both sides. The caliper is probably warped from that amount of heat and then stopping with the pads engaged.

Click to expand...

Follow up:

Ok took all your great advice and replacing pads, rotor and caliper on bad side. The pads have less than 500 miles on them is it still necessary to replace the other side? (I have them anyway) and someone else told me to be sure and check the wheel bearing as it may have overheated. I didnt drive it far at all, maybe 1/4 mile at very low speed then stopped and had it towed. It never got red hot just hot enough to smoke a little. I will at least repack the wheel bearing if it looks ok. Sound good enough hopefully?

Many thanks,
Ken

Good luck repacking the bearings if you have 4WD.

The good news is that you should always replace pads l&r side when doing brakes. The bad news is that if you do have 4wheel drive, those bearings are not a sevice item. If there is play in it, or making some noises, it must be replaced. They run about 140-160 each side, and you'll need a 13 mm. socket 1/2 drive to remove the bearing (3 bolts)This would be better done with air tools. Good luck!

Got real lucky with brakes no damage to rotor or pads. Did not over heat as I stopped as soon as it started smoking. No glazing or cracking. Caliper sprang a leak and pistons stuck. Thats was it. Replacing caliper tomorrow. Wheel bearings are fine no issues at all. Thanks again.

Ken