One piston absolutely would not budge so I installed the brake caliper from Pep Boys. After competing the job and putting the tire back on, I found that the tire would not move - at all. Binding on the caliper. So again Pep Boys sold me a part that does not fit.

When will I learn?

Called Pelican Parts today but the Mercedes specialist was not working. Maybe tomorrow.

Here is a pic of the old caliper. One side piston flat and the other pouched out about 3/4 inch. Not sure it can be rebuilt. Was thinking about trying as Pep Boys core charge is only $4 but with Pelican charging $30 for core do not think it is worth the chance.