Front left Brake Caliper

I recently changed the front brakes on my 96xj as well as the rotors. When I went to push the caliper cylinder/piston back to reset it to allow the new pads to installed I noticed that the face of the piston was cracked missing a small piece. The crack was not all the way through the piston and the piece that was missing was very minor. I finished the brake job and hoped for the best. However, now every time I use the brakes the front left wheel makes a horrible squeaking sound, this is the wheel that had the brake piston cracked. Could the squeaking be related to the cracked piston ? The piston was cracked before on the old pads but the old pads never made any noise. Thanks for your help.

I think the crack itself is not the problem, but perhaps the reason it was cracked before. Something caused it to crack. An overzealous mechanic can crack one of those pistons if it's stiff and doesn't want to retract well, and it's possible that some other brake problem occurred. It might be a good idea to go back in there, make sure the piston moves freely, and also make sure that the rails on which the pads slide are reasonably smooth and free. They can pit, and cause a pad to hang up and not retract. The pads should be a firm fit on the rails, but they need to be able to move too. Of course when you open it up you should also just double check to make sure you put it all together right, and that there isn't something visibly wrong with a pad, and that there isn't a kink or bend in the dust shield that is scraping somewhere, or a little bit of dislodged rust interfering somewhere. It doesn't take much to make a perfectly good brake noisy.

If the crack is too large, it might influence the way the springs on the piston-side pad fit into the hole. Check how everything is fitting together, and if the crack is too big, ditch it. If it's small enough, you might get some improvement by rotating the piston a little so the cracked portion bears on a different part of the pad.

Remember that there are no return springs in a disk brake. The only retraction is from the elasticity of the piston seal. When you push the brake, the seal is deformed a little, and when you let go, it tries to pull back to its normal shape. It's a delicate balance, easily upset. If you're too cheap to replace calipers (as I am for sure) it can be useful every once in a while to take the time to exercise them. The piston doesn't move very far at any one time in use. Pushing the piston back and forth a few times can help a lot to keep them from getting sticky. Just make sure you don't get overenthusiastic and pop the piston right out.

Maybe....but I would take a second look..

Brake pads squeak because of a high frequency vibration setup between the pad and the rotor. XJ rotors are known for warping also. How is the condition of the rotor?

The disc piston is easy to change. Just buy one with a boot and seal...
*remove the dust boot
*pump out the old one
*replace the O-ring, lub with brake fluid and press the piston back in
*replace the dust boot
*bleed, etc...

I would change the rotors if they are grooved.

Update on the caliper rebuild kit:

*available at-
http://www.rigidsteel.com/y30pC3tIGk0.html
*part no. 5252614 should include piston, seal and boot
*price $20.00

It is a wise idea to address front brake issues quickly. Not out of concern for safety, but because the pads will easily wear a groove in the knuckle, and the knuckle is not as easy or cheap to replace as the brake hardware.

for piece of mind, i would get it replaced. you could rebuild the caliper as stated above, or just replace the caliper which is the easiest IMHO. its just two extra steps from replacing the brake pads (removing/replacing the caliper from the brake line).

it is a little more expencive but there is a core charge so you will get something back.

it would be a good time to double check the other side too.

hth

If I replace the caliper do I have to bleed the brake system ? Or does the system remained closed when I replace the caliper ?

If you question the caliper's quality, go to Pep Boys or Napa and get a remanufactured one or both of them. You should be able to find them for under $20 each. The sqeeling could also be a result of the brake pads themselves or the rotor surface. If the pads have square edges on them they can leak to a really annoying sqeal/sqeek. Bevel the edges of the pads and reinstall them. Also make sure that the caliper slides are free if you are not replacing the calipers.

if you rebuild the caliper or replace it you will have to bleed the brake system.

I got reman calipers at Autozone for about 15USD each, they have been working great since.

Regards