Brake Pads - PeachParts Mercedes-Benz Forum

adiaw83 · #1 05-05-2002, 05:40 PM

How hard is it to change the break pads myself. The last person I took it to did not do a very good job and they already squeak. I don't think he replaced the pad wear sensors either. I will also be posting a lot more questions because I finally got a digital camera this weekend and I took a lot of pics. thanks. Check back here often for updates.

DieselHead · #2 05-05-2002, 06:08 PM

I've actually never done the rear pads, but the front ones are really easy because they go in through the top of the caliper. When you change them, make sure to use anti-squeal paste, and remove and replace one pad at a time (as opposed to taking out both, then trying to install both). This makes it easier to compress the calipers to get the pads to fit. Everything else regarding the guide pins, retaining clip and wear sensors should be pretty obvious. Also, it doesn't take very long. Good luck.

Alex

jobah · #3 05-05-2002, 07:56 PM

I concur that it is really easy to do. I, however, have tried a variety of pads. I do not like the US compound OEM pads as they have too much dust and they are not as good as the OEM worldwide compound (has to do with regulations and our lower max speed limit). The best pads that I have ever used are EBC green stuff kevlar pads -- no squeak (although none squeak if done right) and virtually no break dust. Also, best stopping power.

JimSmith · #4 05-05-2002, 08:40 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

adiaw83 · #5 05-05-2002, 09:17 PM

thanks for the help. Right now I have no jack stands. This seems like a problem so how much do these things normall run for?

JimSmith · #6 05-05-2002, 09:22 PM

adiaw83,

I got mine thirty years ago at Sears and cannot remember what they were, but I was a lot less able to afford stuff back then and they were cheap enough to make the budget. Regardless, they are a safety issue so even if they cost $30 now, go for it. Jim

JimSmith · #7 05-05-2002, 11:16 PM

TXBill,

I have done the job without jack stands too, but not on a W126. I did it on my 1975 and 1982 240D's with similar precautions as you cited. Also, I took extra care to keep major body parts out from under the car when I was working. But jack stands make it a lot less scary.

I have always encountered the cover and cotter pins on W123's but can't say I remember what is on the W126 or W201 calipers. I think you are right about the cotter pins. Some cars just have a really tight fit on the retaining pins in the last few mm of travel.

adaiw83,

The wear pad sensors sometimes require a new lead as, if you let pad wear down with the dash light on you can grind away the sensor. I typically change them before they get damaged (they typically light up the dash light when the brake pad material is still there, but thin around the sensor wire, in wet weather) so I don't have to buy new ones. Genuine MB pads come with the features to plug the sensor lines into.

Good luck, Jim