PeachParts Mercedes-Benz Forum - View Single Post

JimSmith · #4 05-05-2002, 09:40 PM

adiaw83,

I once posted the procedure I use to change pads and I think I freaked TXBill out. I jack up the car and take the tire off, then set up to change the brake fluid at the same time I change the pads. I do this every time I do the pads, as MB recommends changing the fluid every two years anyway. The old fluid comes out pretty discolored, so I feel the few bucks I am spending is not wasted.

To do this by yourself with no special tools is something I have worked out over the years. I get a rubber hose that fits tight over the bleed nipple on the caliper, and a glass jar, preferably clear glass. I think the bleed nipple is either 9 mm or 7 mm, and I use a box end wrench. Once the wheel is off the car, I pull the black rubber cover off the nipple and put the wrench over the hex. I usually loosen it first (just to break it loose and then snug it back up) then put the rubber hose/tubing over it and run the other end to the glass jar.

I fill the brake fluid reservoir (Castrol GT LMA DOT 4 or ATE DOT 4 fluid) and then take the various bits of hardware off the caliper to get to the pads. There is usually a cover that you just pry off, then some cotter pin like retainers in the ends of the larger retaining pins that you knock out with a punch or a large nail and hammer, a preload spring that is supposed to keep things from rattling that kind of falls out when the second large retaining pin is knocked out, and then the pads.

As has been noted you take out and remove one pad at a time. I open the bleed valve and then pry the first pad all the way back with a large screwdriver. (edit: I treat the old pad as sacrificial and pry with the screwdriver by pushing it between the pad and the disc and using the edge of the disc as the fulcrum to drive the pad back against the piston in the caliper until the piston if fully withdrawn). With the bleed valve open the fluid runs into the jar and should cover the end of the hose, although sometimes I will pour a little fluid in the jar to make sure no air goes back up the hose/tubing. Once the pad is all the way back against the caliper, shut the bleed valve. Pull the pad out and clean out the area. (edit: I will trial fit the pad in to make sure the new pad won't hang up with that crud on the back and make a mess - if the pad is too tight between the disc and the piston, I put the old one back in and pry to push the piston back in further, and if the new pad is tight between the top and bottom of the caliper it usually means the old brake dust has hardened and needs to be scraped out). Put the new pad in, with or without the anti-squeal goo on the back. I use the stuff and have no brake squealing problems. I also use MB pads. They always fit, no problems.

Once the first pad is in, you repeat the process for the second pad. Once the second pad is in you reassemble the hardware that came off, putting the preload spring assembly in place, then run the two pins in ( the preload spring assembly will pose a minor challenge) , knocking them through the other side so you can get the cotter pin like retainers back on, and then the push the cover on. When it is all done, I bleed that brake by refilling the brake reservoir and pumping the brake pedal. I do this until clear, clean fluid comes out and then I make sure the air is all out. When done, I take the hose off, the wrench off and put the little rubber cover back on, followed by the wheel and tire. Then I repeat the process on the opposite side. The rear pads ususally last more than two years so I bleed the rear brakes to get the old stuff out and new stuff in to finish the job. I think someone posted a sequence for doing the flushing and bleeding that starts with the rear brakes. I think the sequence they cited makes some sense and will likely flush and bleed those first next time.

Hope this helps, Jim