stuck brake caliper

[ericS2the6]

hi,

i have a problem not sure exactly what it is. hopefully someone can please help?

it appears that the rear driver side brake caliper wont completely let go of its rotor. car rolls then comes to a stop by itself. on a slight hill car doesnt roll back when in neutral, but will roll if hill is big enough.

reason i suspect driver rear is because excess brake dust on that wheel, and i hear a clicking noise coming from caliper after driving.

parking brake seems to work fine too, not sure if that could be related.

also side note i had the brakes serviced at the local dealership couple K's ago - new rotors/pads/fluid but i just noticed this problem this week.

thanks if anyone can help

[legacy92ej22t]

I'd jack up the car, take the wheel off and have a look. It could be that it's stuck or not completely releasing. The caliper piston could be siezed up or something too. It's hard to say until you get in there and have a look.

[vrg3]

I agree with Matt... Most likely the caliper is not sliding along its guide pin anymore.

Does the wheel get hot after driving for a while?

[ericS2the6]

thanks i will check tomorrow. what exactly am i looking for? should i be able to see clearance between the pad and rotor. at this point assuming the piston is stuck, is there a way to unstick it or am I in need of a new caliper?

[vrg3]

http://www.graphics.cornell.edu/~v/pics/rearbrakes.gif

I'm guessing that the piston is not stuck, but rather that the caliper is failing to self-adjust.

The caliper slides horizontally along a guide pin and lock pin. That allows it to constantly stay in an appropriate position for braking. This page has a decent illustration of how that happens:

http://auto.howstuffworks.com/disc-brake2.htm

My guess is that your caliper is no longer able to slide along the guide pin.

Take a look at this diagram of the rear brakes on our cars:

http://www.graphics.cornell.edu/~v/pics ... brakes.gif

What I suggest you try is undoing the lock pin (I believe it is a 14mm bolt) and then seeing if the caliper can be swung up on the guide pin. Make sure it can slide freely on the guide pin. It might be good to remove the boots on both pins, clean it out, and put new high-temp grease under there.

[professor]

When the brakes release the pads will still be in casual contact with the rotor, so you really won't be able to see squat, unless the pad or pads have worn noticeably thinner than the other side. It is much more likely that the slider pins are sticking or are dry (they should be greased at every service), or are pitted. I'd replace them first before moving on to the possibility that the piston is sticking. That can happen if the little hole that lets fluid back out gets plugged, due to dirty fluid normally. The warm wheel idea is a good one, if they are rubbing much the wheel will be much warmer than the others

[evolutionmovement]

Worst case new calipers aren't too bad.

Steve

[entirelyturbo]

If you have a stuck caliper, drive on the highway (60-70mph) for maybe a mile, then pull off and go check the wheel you suspect is locked up. If it really is, you should see smoke slowly coming off of the wheel and smell brake pads burning.

I am so fortunate to still have all my orig. calipers and brake MC functioning, as renmaxi lost a caliper and an MC on his 91 turbo. Then my friend's 99 Cherokee locked up its caliper right in my driveway, spent the rest of the day hunting down new calipers and changing them.

[ericS2the6]

after a short drive i checked the wheell i suspected and it was very hot. hopefully i can get it fixed soon

[ultrasonic]

I just replaced my rear pads and rotors. It looks like the calipers were frozen, as the locking pin was entirely corroded and dry. The pads were essentially corroded in place. Luckily the guide pin was clean and smooth, if a little dry.

As a short term solution, I was able to polish the locking pin with a brass wire wheel and lubricate it well. It is working now, but is very pitted.

I'd like to replace the locking pin and locking pin sleeve. Does anyone have part numbers, or better yet, a diagram or list with ALL the brake part numbers?

I've got to say, there is a noticeable difference when the rear brakes actually work! And I think back to when rears AND the fronts were only marginally working. Those first few days after I bought the car and was really wringing it out... If I had known exactly how bad the brakes were!

Also, who knows exactly what is involved with a caliper rebuild? Special tools required? Is it tricky or easy?

Thanks!

[professor]

caliper rebuilds are usually pretty straightforward, as long as the wear situation isn't too bad. If the outside of the caliper is really rusty, that may result in pitting in the cylider bore. That's death for the caliper. Otherwise, you will need the usual tools to R&R as well as a little hone that mounts on a drill to hone the cylinder. Of course the rebuild kit which has seals, fittings, and sometimes a new piston. If the caliper is frozen or wear is bad, sometimes you will need to use a Porta-power to blast out the piston with hydraulic pressure. Check the fluid relief hole for debris, that kills many a caliper when it becomes blocked (this is how fluid gets back into the line when the brakes are retracted). Be sure to lubricate the new seals with brake fluid before installing. Oh, and clean and paint the calipers before installing the new stuff. That'll keep rust at bay at least a little. Also take the time to completely evacuate all old brake fluid, and bleed the other end of the car thoroughly as well. I like the Redline fluid that comes in colors, if you get blue you can see when all the old fluid is gome.

For common calipers I definitely question the logic of rebuilding them yourself. I usually only do them when I can't get a rebuild for a reasonable price (for a 1962 Daimler Dart for instance).

[ultrasonic]

For common calipers I definitely question the logic of rebuilding them yourself. I usually only do them when I can't get a rebuild for a reasonable price (for a 1962 Daimler Dart for instance).

Thanks, professor, that's exactly what I was expecting. New or rebuilt calipers are not that much. I guess when you consider the cost of the kit, and your time, you might as well get a whole new unit.