Changing brake pads - PeachParts Mercedes-Benz Forum

mobenz · #1 11-29-2007, 08:53 PM

I have just looked at the manual regarding changing the pads on my 1978 300CD. How likely is it that I will need specialty tools. I have changed disc brake pads on numerous other vehicles, with only basic tools. Is this that much more challenging?

Thanks

vwbuge · #2 11-29-2007, 08:55 PM

I am not sure of the specifics on your particular model but on my SD it is much simpler than any other car I've owned. No special tools.

pawoSD · #3 11-29-2007, 09:47 PM

I just did the front pads on my car last night. I used:

-Hammer (to pound out the pins and tap in the new pads)
-Heavy Nail (to pound out the clip/pad pins)
-Flat Head Screwdriver (for prying)
-Channel locks (for pulling old pad out and pressing in the piston)
-Needle Nose Pliers (for pulling old pad out)
-6 Shop towels
-Some brake cleaner
-MB Lug wrench to remove wheel
-Torque Wrench to re-install wheel with correct 80ft/lb torque
-Duralast Semi-Metallic Pads from Autozone. They slip right in, have the holes in them for the sensor wires, and cost $19! They also provide as good or better stopping grip than OEM pads in my opinion.
-Some anti-seize goop to put on the back of the pads to prevent squealing
-New sensor wires for any that are damaged/destroyed, I needed two. Two were reusable, two were killed.

(Four needed total)

If you move fast the whole job can be done in about 25-35 mins or less.

TheDon · #4 11-29-2007, 09:50 PM

the pads from Discount auto are lifetime pads I forgot how much I paid... suckers... They work good and.. are lifetime..

pawoSD · #5 11-29-2007, 09:53 PM

Quote:

Originally Posted by TheDon

the pads from Discount auto are lifetime pads I forgot how much I paid... suckers... They work good and.. are lifetime..

Yeah I saw those in my quest for cheap pads, and they are ceramic...thus, they never wear out, but, the rotors will die a horrible and quick death. I'd much rather do pads every year or two than rotors often!

Rotors = pain and expensive to replace!

For the best stopping power and cost effective setup, use soft pads + good rotors. This combination is the best. Pads are cheap.

E300TD99 · #6 11-29-2007, 10:01 PM

I have a 99 E300. I did my rear pads a couple of months ago. No special tools needed. If you have to do your rotors, on mine there is a phillips or allen head you have to take out. If you don't know going into it if you have to replace your rotors, just go ahead and buy them you can always take them back but the new rotors have the minimum thickness stamped in them. I was suprised how easy and relativaly inexpensive it was. $50.00 for rear pads/paste. I didn't replace wear sensors. I don't know if you have those but they just pull out. If I did the rotors, it would have been $160.00 total all purchased from the dealer.

unkl300d · #7 11-29-2007, 10:04 PM

If you need to remove the caliper for some reason, you may need a leverage
pipe to fit over the socket wrench. The retaing bolts in back are sometimes tough to loosen.

vwbuge · #8 11-29-2007, 10:16 PM

Channel locks work good for pushing the piston back in. I did the front rotors and pads on my Subaru and I used a large C clamp to push the piston back in. I just flip the old pad over and use it as a base on the piston so it goes back in evenly.

JimSmith · #9 11-30-2007, 11:13 AM

Long ago I wrote a detailed procedure for changing pad on W123 chassis car's brakes. It was apparently a TXBill originated thread and at some point in time when TXBill left the forum he had all of his posts deleted, including many with input from others. My brake pad replacement procedure was apparently one of the many casualties of that act.

So, I will try to write another one.

First, I change the brake fluid in the lines to the calipers I am going to change pads in at the same time. The manuals say to change brake fluid every two years, which typically corresponds to about the life of a set of front OEM pads if you drive reasonably aggressively. I use Castrol GTX LMA Dot 4 or 4+ brake fluid, exclusively. It is inexpensive and works very well. There are other brands, some cost more and some less, that are all likely fine too. My experience is with Castrol's product though, and it has been good for more than twenty years.

So, go buy a couple of small bottles of brake fluid. Or one larger bottle. But buy enough so that you don't run out. If the fluid has never been changed, you may need more to really flush out the lines.

You will also need a 9 mm or 7 mm box end wrench to fit over the caliper vent nipple, and a liquid penetrant like WD-40 or PB Blaster or the like to spray liberally around the caliper vent nipple. You will also need about a two foot length of tubing that fits tightly over the vent nipple - something like a 3/16" ID, that is rated for brake fluid and oil. The rest of the tools you will need consist of a lug nut wrench to remove the wheels, a jack and jack stand, a needle nosed pair of pliers, a large nail or a punch, a hammer and a large, flat, screw driver. I also get a medium sized screw driver and a wire brush for scraping the caliper guide surfaces of rusty, hard depsits of brake dust and disc wear products. I also make sure I have some synthetic, high temperature, brake parts grease and anti-sieze compound, also rated for brake duty (high temperature). These are available from NAPA and other parts stores. Finally, you will need a small glass jar, like a jelly jar or something that can hold 8 oz. or so but it relatively tall and narrow.

So, I block the car wheels I am not working on, loosen the lug nuts on the wheel I am going to work on, and jack the car up high enough to get the wheel off. I support the car on jack stands and remove the wheel, then pull the rubber cap off the caliper nipple and spray the penetrant all around the base of the nipple where it threads into the caliper. I let that sit for a while, then I put the box end wrench over the nipple and tap it with the hammer to try to break it loose. Once broken loose, I put the hose over the nipple and run the other end of the hose to the glass jar, making sure it is out of the way and the hose end rests on the bottom of the jar. Leave the box end wrench on the nipple, and try to find a location that allows at least a quarter turn of the wrench, so you end up with the hose kind of blocking removal of the box end wrench.

Next I pull out the cotter pins in the brake pad retaining pins that are driven into the calipers from the inside. I use a needle nosed pair of pliers for this.
Then I knock the pins in the caliper out, first just tapping them toward the inside of the car with the hammer and then I use the nail or a punch to drive them out of the caliper. You will see how they fit in the grooves of the retaining/anti-rattle spring, and will likely have to apply some pressure with the large screwdriver to the edge of the spring to get the pins to clear and come out. Not a big deal.

Once both pins are out, the spring comes out (it can actually be removed when the first pin comes out most of the time), and now you see the worn out pads pushed toward the disc and away from the inner surfaces of the caliper.

Next it is important to get in your head that you will be changing one pad at a time. If you try to change both at the same time, meaning you take both pads out of a single caliper at the same time, the process of backing the caliper piston in on one side will extend the piston on the other. With no pad to keep its range of motion in check, it will likely pop out. That is not the end of the world, but it makes this job one whole lot more expensive and expansive. So, remember to do remove one pad, replace it, then remove the next pad and replace it.

Start this part by filling your brake reservoir with fresh Castrol GTX LMA brake fluid or your choice of fluids.

To remove the first pad, you crack open the vent nipple about half a turn or so and then slide the big screwdriver between the disc and the old pad. Pry against the outer edge of the disc to push the pad, and behind it, the piston, back into the caliper bore. If this is overly difficult, open the vent nipple some more. As you back the pad away from the disc, the hose will fill with fluid and drain into the jar. The fluid will be strongly discolored, likely a dark brown or black. The new stuff is barely a light yellowish hue, mostly it is clear. Once the first pad is firmly pushed all the way back, close the nipple.

Pull the pad out of the caliper with your fingers, or use the needle nosed pliers and the smaller screw driver to wiggle it out. Once it is out you need to invest a few minutes cleaning the flat surfaces it rides against. I use the smaller screw driver as a scraper and the hammer to chisel away any really hard lumps of corroded on junk, and keep at it until there is no evidence of this junk in the areas of contact between the steel backing of the pad and the guide surfaces on the caliper. I try to brush it out good with a small wire brush. Then, I trial fit the new pad. If it won't fit, in my experience (I use dealer supplied brake pads) it is always that I have not pushed the piston all the way back into the caliper, and that is almost always due to the build up of that corroded on crud behind the pad backing on the caliper guide surfaces. It prevents the pad from going all the way back. So, since I have cleaned this away I put the old pad back in, open the vent nipple, and using the screwdriver to push the pad back further, fully recessing the piston in the caliper. When the new pad fits in nice and snug, I remove it, apply a light coating of that high temperature brake part grease to the caliper guide surfaces and a heavier dose to the back of the pad. Then I carefully slide the new pad into place.

If there is any extra grease squeezing out, I wipe it away from the disc onto the caliper.

Now you go to the other pad and repeat the process. If your car has brake pad wear sensors you need to put them in before installing the pads. At this point I put the spring clip back in position, knock the pins back in (sometimes, ok, all the time, you have to push the spring hard against the pads with a screwdriver - the bid one - while pushing the pins in) taking note of the cotter pin hole orientation - it is easiest to get the cotter pins in if the holes are vertical. The pins are only tight at the last eighth of an inch or so, in the bore of the caliper, and that is only on the inboard side. So, if you push the spring back you can manipulate and guide the end of the pin into the hole on the other side of the caliper. Once both pins are in, put the cotter pins in.

Once the second pad is in and the pins are in, I bleed the brakes. I go ensure the brake fluid reservoir is topped off, and then look to see the hose end is covered with fluid in the jar. I will back the vent nipple out a few turns, dab some anti-seize compound around the threads of the vent nipple to seal them off and run it back into position where a quarter turn or so takes it from closed and sealed to venting. With the caliper vent open, I step on the brake pedal, and pump it several times and check the fluid level in the brake fluid reservoir. Don't let the reservoir level get too low.

If you have a helper you can then begin the bleeding process - you ask your helper to push down on the brake, open the nipple, let the helper's foot go to the floor, close the nipple, and tell the helper to lift his foot. You do this several times and then stop to check stiffness of the brake pedal and the color of the fluid coming out of the hose. The fluid should be nice and clean coming out, while the jar should be filling with relatively dark solution of old nearly black stuff and a bunch of new stuff.

Repeat the brake pumping and vent opening and closing until the brakes feel good. If you have no helper, you can do this alone by ensuring the hose end in the jar is always submerged in fluid, and then pumping the brakes your self. Since the line will gravity drain from the brake fluid reservoir under the hood to the glass jar you have to be alert about the fluid level in the reservoir. But, pump the brake a few times, get out, close the vent line, check the brakes, repeat as needed until the brakes feel fine.

Once done, tighten the vent nipple down, remove the hose and the wrench, dab some more anti-seize compound around the vent nipple to caliper interface and pop the vent nipple cap back on. Put the tire back on and remove the jack stands and lower the car the ground.

Repeat at the next brake. The rear brakes are very much the same, perhaps a bit smaller. I do them at least every other time I do the fronts, as leaving the pads in place in the Northeast for many winters just makes the burned pad carbon/steel wear products and salt spray more likely to freeze the pistons in place and ruin the function of the rear brakes. Pads and brake fluid just are not that expensive. I hope this helps.

Jim

Dee8go · #10 11-30-2007, 11:24 AM

The rear pads on my 300TD were really easy. I haven't had to replace the ones on the front yet, but understand they are slightly more involved.

winmutt · #11 11-30-2007, 01:34 PM

Get 2L of brake fluid and flush the system thoroughly. The stuff is cheap and rarely flushed.

TheDon · #12 11-30-2007, 02:10 PM

Quote:

Originally Posted by pawoSD

Yeah I saw those in my quest for cheap pads, and they are ceramic...thus, they never wear out, but, the rotors will die a horrible and quick death. I'd much rather do pads every year or two than rotors often!

Rotors = pain and expensive to replace!

For the best stopping power and cost effective setup, use soft pads + good rotors. This combination is the best. Pads are cheap.

I don't think they are ceramic.. they leave a nice brake dust powder after 2 weeks of driving

pawoSD · #13 11-30-2007, 02:16 PM

Quote:

Originally Posted by TheDon

I don't think they are ceramic.. they leave a nice brake dust powder after 2 weeks of driving

Thats good, you'd probably know it if they are ceramic, they usually require a bit more force when braking.

My Autozone Durlast Pads are now broken in, and they are phenominal. I can smoothly decelerate from 70+ to 0 with not so much as a shudder or vibration at all. They are VERY grippy, it takes very little force on the brake pedal to slow down the 2ton beast. (weighed it the other day, 4200lbs with me in the car and half tank of fuel! I am only 175ish

) They are made in USA too. For $19, I am completely impressed. As is usual with autozone, it seems to be hit or miss. The starter we got from them for our 300D works great as well....

Another thing the new pads solved was my long-time (25,000 mile+) cause unknown shudder when slowing down, it only happened between 23-17mph while slowing down, didn't matter how hard I was slowing down, but it always happened. Kindof a "quivering" through the whole car. With the new pads, its gone. 100% gone. I am very very glad about that!!

My pads were free because I had an autozone rewards credit from past purchases. Cheapest repair ever! $0!!