DIY pad/rotor replacement '00-'03 ML430/ML55/ML500

Updated a bit 6/03

It seems like I just did this, why am I already changing front rotors again, less than a year later? The answer to this question can be found here. Someone ran a red light, rolled my wife, and the ML, upside down, and the truck was totaled (my wife was fine, the idiot that hit her didn't have insurance though and his passenger left via ambulance with whiplash). I bought a used ML55 to replace the 430 and now at 53k miles the 55 needed new front rotors. So I took a few more pictures and compared my experience the second time around, adding a few new observations.

DISCLAIMER:Working on your own vehicle can be dangerous and can cause severe injury, death, and/or dismemberment. The author assumes no liability for any and all problems that you might encounter by following the suggestions contained on this page. The author is not a certified mechanic and makes no claims about his mechanical competence even if his young kids think he can fix anything. I recommend that you wear safety glasses, use gloves, wear steel toe boots, wear thick denim pants, wear a long sleeve shirt and also use a hard hat. I wore sandals, shorts, and a tee-shirt but you can never be too careful.

Ok, now that the usual disclaimer is out of the way here's what I did.

I ordered a new set of stock front rotors and pads from. Two days later a 58 pound box arrived from Brown with some shiny new rotors in Brembo boxes and some pads in a Pagid box.

Step #1: If you're doing this surgery in the afternoon I would suggest opening a properly chilled micro brew, preferably something that's hoppy and dark yet not too perniscious (see disclaimer above once again). Since I started at 9 am and I didn't want my neighbors talking about me again, I skipped the beer part.

Jack the truck up, put it on stands, remove the wheels. It should look something like this if you did everything correctly.

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Step #2: Make sure the beer is still cold and then take stock of the situation.

Figure out where the important parts are on the caliper. These are the first bits that you'll be removing since they need to come off before you remove the caliper.

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Step #3: Remove the sensor wire, pins, and clip

The pins are removed by inserting something ($.99 phillips screwdriver worked for me)into the small hole on the face of the caliper and using a persuasion device (hammer worked for me) to pound the pin out the back side. Depressing the the clip (with a thumb)towards the edge of the rotor helps.

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Step #4: Isn't it time for another beer? You're working hard and you deserve one. It's time to remove the caliper. Resist the urge to wash your hands.

To remove the calipers you need to remove two large mounting bolts that are located on the back of the caliper. They are metric and somewhere around 20-21mm but I couldn't find the right socket. A 13/16 socket works in a pinch.

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These bolts are pretty tight and have signs of Locktight on the threads. I had to break out a cheater bar to get them loose.

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Once you've removed the bolts you should have a small collection of small bits that looks something like this.

Now it's time to remove the pads form the caliper. This has to be done so that you can pull the caliper off of the rotor. Remove the pads by compressing the brake pistons (see picture in Step #6 for details of the brake pistons).

A flat screwdriver wedged between the pad and the rotor provides enough leverage to push the pistons in. The pads will now slip right out of the top of the caliper.

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Step #5 Get something to support the caliper once you remove it from the rotor. You don't want it hanging by the brakes lines. Resist the urge to wash your hands.

Swing the caliper over the top of the rotor and rest it on your support.

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Step #6: How's that beer holding up? It's time to remove the old rotor.

There's a 5 mm allen (hex) bolt on the face of the rotor that attaches the rotor to the hub. Remove it.

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There are two "slugs" that also attach the rotor to the hub. These need to be pounded through.

 

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UPDATE: Those slugs are actually called "roll pins" and don't neccessarily have to be removed. My rotors were stuck/rusted on pretty well. Maybe if I had spent more time with the hammer they would have loosened up.

::update:: I had to remove theroll pins on the ML55 as well and really had to whack the rotor with a heavy hammer (big ole framing hammer) to get the rotor loose from the hub.

One added benefit of whacking away with the hammer is that is loosens some of the accumulated clay and mud frome the underbody.

 

I'm sure the Mercedes folks have an expensive tool for this procedure but I just used a 3/8' extension and a hammer to pound the slugs through.

Once you pound both of them through you need to pull the rotor off. Mine was still adhered to the hub by rust so I got to bang the snot out of the rotor face (by the mounting holes) too loosen it.

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Your truck should look something like this at this point (maybe a bit blurrier depending upon the beer situation).

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Step #7: Put the new stuff on. Now you're a pro. All you have to do is reassemble using new parts. Resist the urge to wash your hands.

Hang rotor on the hub using the 5mm mounting bolt

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Step #8: Things are going pretty well. You probably deserve another beer at this point. Pound the slugs in.

The slugs are tapered on one end. Insert that end through the rotor and into the hub. Wack into place with a hammer.

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Step #9: Prepare the brake pads. Resist urge to wash your hands.

Mercedes uses a grease-like substance as an anti-squeel agent. I didn't have any so I used a generic latex-based spray to coat the back of the pads.

While these are drying, go to Step #10 or have another beer and watch them dryand then go to Step #10.

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Step #10: Slip caliper onto rotor and attach it by tightening the caliper mounting bolts.

Step #11: Push brake pistons all of the way in so that it is easy to insert the new pads. The easy way to do this is to use the old wafer thin pads and a piece of wood to push both pistons on one side in an equal amount. If you just push one piston in the other piston will pop out.

Step #12: Insert brake pads, place clip between pads, pound pins back into place, and insert brake wear sensor into new pads.

Step #13 Insert wheel hanger into new hub to make mounting the wheel much easier.

It's too bad that Mercedes doesn't include one of these beauties with the truck. click to enlarge

Step #14: Now is a good time to check your tire for unwanted passengers.

Thankfully, it was a little guy and didn't cause any damage. click to enlarge

Step #15: Mount tire, wash hands, test drive (depending upon the beer situation you might want to wait until the morning)and then "condition" the rotors for a few hundred miles avoiding avoiding heavy braking. Then bed the pads by making 3-4 hard stops from 80-100 mph.

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Doing the rears (from the internet):

"The rear rotors need to have the e-brake released prior to removal. Shine a flashlight in through the lug holes and slowly rotate the rotor until you see a small star-wheel. This is the adjuster for the e-brake, use a small slotted screwdriver to rotate the wheel, I forget which direction, so you must rotate the rotor after a few clicks. If it stops turning, go the other way. After the new rotors are installed, turn the wheel in the other direction until you feel the e-brake dragging on the rotor, then back off 3-4 clicks."

So, how big are those front rotors anyway?

Just slightly larger than 911 Turbo rotors.

 

This page and all images © Pete Fagerlin 2002, 2003 and may not be copied, redistributed or reproduced in any fashion without my prior written consent. Linking to this page is just fine, of course.