Mercedes ML350
Replacing Front and Rear Brake Pads
By Paul Waterloo
Replacement of front and rear pads on the ML350 is an easy task, even if you've never done it before. You might also have to change the rotors if they are below minimum thickness, but I did not have to. When replacing pads only, I do not have the rotors turned, I just replace the pads and let them bed in by normal means.
If the front brake pads are worn down, the rears are probably not far behind. I always do both at the same time. On the ML350, the fronts and rears both have wear sensors on the right hand side only. If you get the pad warning light, it could be the front or the rear sensor.
The following procedure shows an 07 ML350 with dual piston front, single piston rear calipers.
Tools Required
9mm hex head tool, best to get one that will accept a 3/8" drive socket (this is NOT easy to find)
7mm hex head tool, best to get one that will accept a 3/8" drive socket
7mm hex head tool, wrench style for rear
Large "C" clamp to push the piston back in the caliper
Brake caliper lube for guide pin if not replacing the pin
A few screwdrivers, channel locks and vice grips if you don't have a 7mm all head wrench
Brake cleaner and rags
Why not change the brake fluid while you are at it?
I always change out the brake fluid when changing pads. It just makes sense. It's super simple, follow the procedure here.
If changing the brake fluid, you'll need a plastic hose and 11mm flare wrench.
Procedure
The basic procedure for the front (which is the same as the rears) can be found here. Loosen lug nuts. Jack the car up and put front end up on jack stands. Raising the entire front end makes the job much simpler and safer. Remove wheel.
Front Brake Assembly. Note how the spring clip is installed. The rear brake is almost exact but smaller. The stud sticking out is with the spare tire, screw it in after removing a lug nut, it helps to put the wheel back on again.
Using a pair of pliers or screwdriver, remove the retaining spring.
Once the carrier bolts are removed, you'll have to get the caliper free. Rock it back and forth with a large screwdriver, spray some brake cleaner on it to help clean it, and also put the screwdriver between the rotor and brake pad to push the pistons back slightly to gain clearance. It should come up with relative ease.
Once the caliper is off, you'll need to push the piston back into the caliper. Use the old pad and slowly push it back in.
Clean everything up, insert the piston side brake pad into the caliper pistons, and the other pad on the brake assembly so it's touching the rotor. Lube the guide pins after cleaning them (or I would recommend replacing them as the procedure states, guide pins that have rust on them will only cause trouble) and reinstall everything.
After doing two wheels, I like to start the car in park, and then push the pedal until it is firm. While doing this procedure, make sure that the master cylinder does not over fill!
Front pads, pad on right inserts into pistons.
Pad Wear Sensors
The pad wear sensors are located on the right hand side only, both front and back. You'll need to buy new wear sensors as they are not part of the brake pads. They are a great design, just plug into a fit on the pads, and plug in right at the caliper. Pictures below are self explanatory.
Notes on Rear Calipers
The rear is the same as the front, but have a 7mm carrier bolt. The lower carrier bolt cannot be accessed with a standard 3/8" drive and hex head due to A arm lack of clearance. I used a pair of vice grips to get the lower carrier bolt out attached to the 3/8" drive, if you have a 7mm allen wrench, that would work great. Be aware, most kits do NOT come with a 7mm allen wrench. Sears sells a kit with both 7 and 9mm allen wrench, I suggest getting this for the job.
