MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
Last updated:
In this guide (5 sections)
This guide shows how to replace the front brake pads and rotors on a Mercedes-Benz M-Class W163. The photos and video cover the repair step by step. You will also find a DIY video at the end of this article. The rear brakes on the same truck are a separate job, covered in our guide to replacing the rear brake pads and rotors on the ML.
This guide applies to the Mercedes-Benz M-Class W163 chassis:
Models: ML320, ML430, ML55 AMG, ML350, ML500.
Years: 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005.
Parts required:
- Genuine Mercedes-Benz Front Brake Pads
- Front brake rotors, matched to your caliper type
- Brake pad wear sensor, if the old one is damaged
Before replacing parts, inspect the condition of the brake pads and rotors. While brake pads are easy to inspect, rotors require that you measure the thickness of the disk to see if it is within limits. Specification values are shown in the Brake Rotor Thickness table below. Make sure to also check for hairline cracks and scores. Warped rotors may be hard to inspect visibly, but steering wheel or brake pedal vibration during braking can indicate rotor runout or thickness variation. Measure and inspect the rotors before replacing them.
You can easily measure the thickness of the rotors using a caliper gauge.
| Model | Floating caliper, chassis 163.113 / 136 / 154 / 172 | Fixed caliper |
| Thickness | 25 mm new | 32 mm new |
| Wear Limit | 23 mm, replace at or below | 29.4 mm, replace at or below |
Step by Step: How to Replace the Front Brake Pads and Rotors
- Open the hood.
- Locate the brake fluid reservoir (Hint: The brake fluid reservoir is near the firewall on the driver’s side.). Unscrew the cap from the brake fluid reservoir.
- Set the parking brake and chock both rear wheels, then jack up the front of the truck and support it on jack stands before you take the wheel off. The parking brake on this chassis acts on the rear wheels, which stay on the ground for front brake work, so it does hold the truck, but the chocks are what stop it rolling if a stand shifts.
- Inspect: Check brake pad thickness and condition of rotors. Check for brake fluid leaks. Check dust seals for damage.
- Remove the brake pad wear sensor connector. If the sensor is worn, showing bare wire, you must replace it. Otherwise, it can be reused.
- Get ready to remove the caliper. There are two front caliper types: fixed and floating.
Fixed Caliper: You will need to use a drive pin punch tool.Floating Caliper: Remove the two guide bolts. They take a T40 male socket from a T-Socket Tool Set. - Remove the caliper together with the brake pads. Be careful not to twist the brake hose too much. You should tie the brake caliper to the suspension component so that it is not hanging and putting pressure on the hose.
- Pay close attention to the old pad’s position so that you install the correct pad on the correct side. The pads are different for left and right.
- If you are replacing the rotors, the caliper carrier bracket comes off next. Two large bolts hold it to the steering knuckle. With the bracket out of the way, back out the single countersunk screw in the face of the rotor and pull the rotor off the hub. A rotor that has corroded onto the hub will usually come free with a few taps on its face, between the studs, using a dead blow hammer.
- Wire brush the hub face before the new rotor goes on. Rust or grit left under a rotor holds it off square, and that shows up later as a pulsation through the brake pedal. Fit the new rotor, run the countersunk screw back in, then bolt the carrier bracket back on, to the torque given with the caliper bolts below.
- Check the reservoir level before retracting the pistons. If it is near MAX, remove enough fluid with a clean brake fluid-only suction tool to prevent overflow. Press the pistons back squarely into the caliper with a Brake Caliper Press or any piston pusher.
- Clean the contact surface of the brake pads in the caliper. A metal brush works well.
- Fit the new pads in the positions you noted, left pad to the left side and right to the right, seated in the caliper the way the old ones sat. Refit the caliper over the pads, then plug the wear sensor connector back in.
- Install the caliper guide bolts and tighten them with a torque wrench. Mercedes service data gives 30 Nm for the floating caliper guide bolts on most of these trucks and 25 Nm on some earlier configurations, so confirm the figure against your own chassis number before you pull on the wrench. The large bolts that hold the caliper carrier bracket to the steering knuckle are a different fastener and a much higher figure, 180 Nm.
- Refit the wheel. Start every bolt by hand, lower the truck until the tire just touches the ground, then tighten the bolts in a crosswise pattern with a torque wrench.
- Close the brake reservoir cap.
- NOTE: Once you install the pads and/or rotors, start the car but do not drive. Press the brake pedal several times until the pedal feels firm. Do not move the vehicle until normal pedal pressure is restored.
- Check that the brake fluid level is between the MIN and MAX marks.
- Do the other side before you drive the truck. Front pads and rotors are replaced in axle pairs, so the second wheel gets the same job.
- Go easy on the brakes for the first few hundred miles. New pads and rotors need some gentle use to bed in before they give their full bite.
Video: Front Brake Pads and Rotor Replacement, 1999 to 2005 Mercedes-Benz ML
How to Clean and Reinstall Rotors
Related Part Numbers:
Front Brake Pads
A 163 420 03 20 GENUINE MERCEDES-BENZ OEM FRONT BRAKE PADS SET ML320 ML350 ML430
Is the ABS warning light on in your Mercedes-Benz’s dashboard? Use a YOUCANIC Scanner to read fault codes and fix your brake system like a pro!
Before you buy parts, scan every control module, not just the engine. It shows the root fault behind the warning lights and tells you whether the problem is still active. See how to do a full health check.
