adiaw83,

I have posted a method in the past. But the idea is to change the brake fluid when you do the pads, so put a 9mm box end wrench over the vent fitting on the caliper, then put small, say 1/4" inside diameter rubber hose (like the line going to the prefilter on the the way to the fuel injection pump - I have a spare length I use for this) over the nipple. Then run the other end of the line to a jar, and open the vent. Use a large screw driver (I use a large Craftsman slot head screwdriver from Sears) positioned between the disc and the pad, with the end of the screwdriver about the middle of the pad, and then pry it away from the disc. Go ahead and chew up the pad as you are not going to use it again. I try not to damage the disc or pry against it in the area the pad sweeps. Once the pad begins to move, with no back pressure it will go all the way back, driving the piston all the way into its cylinder bore. Once the pad is all the way back against the caliper guide surfaces, close the vent line.

Remember to replace the pad with a new one before going to the other side, or you may pop the piston you just pushed in back out a little. With the vent open, you don't generate much pressure so it is unlikely you will really pop it out.

As noted above, really clean the crud out of the cavity the pads go back into. If you leave old burned pad material and disc grindings, it will make the fitting of new pads very difficult, and could contribute to binding or other brake system functional problems.

When I am done on each side, I bleed each brake out through the vent lines before going to the next caliper. I am always in awe of how dirty the stuff looks compared to the clean stuff that goes in the reservoir. I flush until the clean stuff comes out and then I just make sure no air leaked back in.

Hope this helps, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)