Originally Posted by tyl604

First post - On my 2002 GS300 I need front brake pads. On the passenger side everything was fine until I tried to compress the two pistons with a C clamp using the two old brake pads as buffer; done this many times on the Mercedes. Although I was trying both at once, the back piston just would not budge. So I compressed the front one and, doggone it, the back one popped mostly out and showed about 1.5 inches of rubber. Got it back in but now there is a leak. And I was never successful in getting both to push in together.

Are you supposed to open the bleed screw to do this? Of several videos and stickies, only one mentioned the bleed valve. This would certainly have released the pressure on the sticky piston.

Finally I clamped the back piston and pushed the front piston in enough with a screwdriver to clear the brake pads. Then I slid the caliper up to the back piston, pushed it in with the screwdriver and slid it over the brake pads. I put it back together, the pulled the caliper back again just to check. Sure enough it is leaking.

Mechanic wants $75 for a new caliper (says they cannot be rebuilt) and $150 labor.

What did I do wrong? Used a C clamp to push both pistons at the same time. What could have caused the back piston to be such a problem; could it have been malfunctioning all along? Inspecting my pads on that side, I find a pretty good but thin one but the second pad is down to the bone and shows some evidence of metal to metal. Do not see how one sticking piston could have caused this uneven wear but is this possible?

Should I buy a rebuild kit for $5 which I see online at a parts house?

Appreciate your thoughts.