Weird Caliper Issue
 

The front left caliper on my '94 E420 is acting up on me. There is some uneven pad wear. I’ve done pads, rotors and even rebuilt the calipers to no avail. After the most recent pad change there is a prominent squeek/groan at very low speeds (basically rolling at idle). Is it possible that one or more pistons have gone bad? And by that I mean could it have been damaged or worn such that it doesn’t ride perfectly smoothly? Are these replaceable parts?

Have you ever replaced the rubber brake hoses? I did mine and it greatly improved the braking. You may have a hose that is balloning and when the pedal releases the line shrinks but the caliper stays put.

Tim

When was the last time the brake fluid was flushed?

After years of old fluid rust will form between the piston and the bore and the piston sticks. If is fairly easy to fix if its done before the piston siezes in the bore. Sometimes just moving the piston in and out a few times will clear up the problem but to do it right the piston should be removed and cleaned up.