gt4awd

Several months back we changed out the front brake pads without any issues. Go to do the rears today, and the setup is the same. Pop out the two pins, and compress the pistons. Finish up the passenger side without any problems. However, did have to open up the bleeder to let fluid out. Only way to compress the inside piston. Go to do the driver side rear... Get both pads out, and compress outside piston no problems. Place new outside pad. Here's where everything goes downhill. We go to compress the inside piston, and it will not budge at all.

Happened to have a mechanic friend there who has built drag cars from chassis up, and right away he suggests the caliper must be seized up. I had him hit the brake pedal a few times with vehicle off, and the outside caliper closes up after removing the new pad. Now neither of them will budge at all. Tomorrow we plan to remove the entire caliper, and use a heavy duty c-clamp to try and compress the pistons. I wanted to see if you guys think this caliper is safe to use even if we managed to open the pistons, and place new pads? Do you think the caliper is bad? What steps should I take to diagnose? As of now my c32 will sit until the problem is sorted out of course.

gt4awd

Searching around it seems even the rear calipers are AMG specific. All the calipers I'm finding appear to be single piston with one pin. The rears on C32 have two pins. I don't want to know what new ones will cost at the dealer...

doom239

Try Starting the car up and stepping on the breaks and hit the e-Breaks to.
Maybe the car needs to have fluid pumped first.
Just a thought?

gt4awd

I appreciate you trying to help doom239, but that wasn't the case. Thanks for trying to help out! We worked a few hours struggling to budge the stuck pistons loose without any luck. Had bought a medium piston tool. Could apply a lot more force with it. Bleeder open on the caliper. No fluid escaping other than a slow drip from the brake line. Called it a night after much disappointment, and frustration.

After work today my brother picked me up, and we went back to work on the rear driver side caliper. Removed the two main bolts, rotated caliper after loosening brake line to disconnect the line. Caliper off completely. Took it to several auto parts store Autozone, and checkers. Neither had a tool that would work on these specific calipers to compress the piston. Went to Brake Masters who told me they couldn't work on the caliper at all, and it was 100% no doubt seized up.

Take it back to the house, and separated the caliper into both halves. Cleaned internals by spraying brake cleaner. After doing so I was able to compress the inside piston that originally opened up. Using a large 6" c-clamp on the other section no luck at all still! Enough force to bend the small end bar that you turn with by using a medium pipe to turn it. I was ready to give up, and even considering taking a hammer with rubber shield to beat the piston. I end up closely examining the piston, and notice it is slightly tilted on one side. Use the c-clamp to press the side extruding up, and with little force the caliper popped back into the correct position. Almost no effort was required to fully compress the piston after doing so...

gt4awd

Just got back from my brothers place. Brakes are working good! Checked for leaks, and none found... I did use Prestone Dot 4 brake fluid as I didn't have any Mercedes "Dot 4 Plus"... I'm sure the Prestone will be just fine. After reassembly bleeding the brakes manually at least seven times each to ensure no air was in the lines or calipers. Another small issue did show up after doing the brake job. Hoping someone will be able to help out with this. For some strange reason my shift lock tab under the coin holder now clicks when I hit the brakes in park? Other than the sound nothing seems to be effected.

doom239

Nice Glad you found the problem.

TemjinX2

you gotta love the quirky germans. There's always some trick. I learned none of there items really require brute force, but some trick that makes things go easy.

loudandheard

I think the first job I did on my car was the rear brakes. I didn't have any issues and I did use a c clamp to compress the caliper. I found it so weird when compressing the caliper, that no fluid increased. I'm glad you were able to figure it out.

gt4awd

I think the issue was due to trying to compress the pistons on just one side. If you were to leave the old pads on to create a flat surface and compress them that way this shouldn't happen. That's what I did on the fronts, and no problems. However, if a piston does get stuck it's likely the same issue I had, and not seized up. Just closely examine to see if the piston looks tilted slightly. If so, use a c-clamp to compress the side up more. The piston itself must have snagged up on the caliper wall.

loudandheard

I hate to bring a thread back from the dead, but I'm having a few issues bleeding my brakes. I recently did new rotors, stainless steel brake lines, and new pads on all four corners of the car.

I used my mityvac to try and bleed the brake lines, but I never got a steady stream of brake fluid. I did all 4 corners and I though I was good, but when I test drove it the brake pedal felt very soft.

Is there a special process involved in bleeding the brakes. Maybe I didn't bleed them enough times. Hopefully it's just air in the lines, I can't think of what would make the brake pedal feel so soft. I'm also getting an esp error, but I think that will go a way on it's own.

What do you recommend to do?

gt4awd

I recommend manually bleeding each brake around five to ten times. Requires two people. One in the vehicle to hit, and release the peddle. Other to open, and close the bleeder valve. Call out open, and open the valve while the other person presses the peddle all the way down. Say closed when the valve is closed, and other person releases peddle. Repeat until steady stream with no sputtering.