MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
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This guide provides instructions on replacing the rear brake pads on a Mercedes-Benz SLK R171.
These instructions apply to the following Mercedes-Benz R171 SLK models.
- 171.454 Mercedes-Benz SLK300 2009 w/ Sport Package
- 171.458 Mercedes-Benz SLK350 2009
Tools Required
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Jack Stands: Best Selling Jack Stands List |
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Hammer. Yes, you will need one. |
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Pin Remover Removal Extractor Tool |
Parts Required
- Rear Brake Pads. Ceramic Recommended 003 420 27 20 0034202720
- Rear Brake Pad Wear sensors.
- Brake pad anti-squeal grease.
- Rotors (if you plan on replacing them).
Check any pad or sensor part number against your own VIN before you order. Brake pads are chassis specific and a set listed for another Mercedes model will not fit an R171, even where the pictures look the same. Your dealer parts counter will confirm a number from the VIN in a minute and the call costs nothing.
Watch: Mercedes-Benz Rear Brake Pad Replacement Guide
How to change/replace rear brake pads on SLK300 SLK350
- Loosen the rear lug bolts while the car is still on the ground, then jack it up at the lift point for your car and lower it onto jack stands. Chock the front wheels. Do not set the parking brake for this job. It works on the rear wheels, which are the ones you are about to take apart, and it will hold the hub and get in the way of the caliper.
- Open the hood and remove the cap from the brake fluid reservoir. This will allow the brake fluid to return to the reservoir when you press the pistons into the brake caliper. Note the location in the top right corner, marked “Brake Fluid”.
Location of power steering fluid, coolant, brake fluid, and windshield washer. - Remove the rear wheels.
- Remove the brake pad wear sensor from the right brake pad.
- Use a hammer to remove the pin that holds the brake pads in place. As you extract the retaining pin, be careful not to hit the brake heat shield. If you hit the shield, you may bend it and cause it to make noise when you drive.
- Press the caliper piston back into its bore. A piston press or a wide flat bar spreads the load evenly. If you use a screwdriver, lever against the face of the old pad rather than against the piston or its rubber dust boot: a nicked boot lets water into the bore and the piston seizes later.
- Remove the old brake pads and clean the area where the brake pads make contact with the caliper.
- Install the new brake pads. Apply brake grease on the area where the brake makes contact with the caliper. Keep grease off the friction face of the pad and off the rotor; it belongs only on the backing plate and the contact points. Install the retaining pin, aligning the pads first, and tap it into place.
- Install the wheel and lower the car. Make sure to tighten the brake fluid reservoir cap.
Before you drive the car
Pump the brake pedal until it goes hard. This is the step that gets missed and it is the one that matters most. Pressing the pistons back into the calipers leaves the pads sitting away from the rotors, so the first time you press the pedal it will sink much further than normal and the car will barely stop. With the engine off, press the pedal repeatedly until it comes up firm and stays there. Do that before the car moves at all, not at the end of the driveway.
Then check the fluid and the bolts. Put the reservoir cap back on and look at the level, because pushing the pistons back sends fluid the other way and the level can end up high. Tighten the lug bolts in a cross pattern rather than around the circle, and finish with a torque wrench set to the figure in your owner’s manual or from the dealer. Both are worth doing properly: a rear wheel is not something you want to find out about later.
Give the new pads a gentle first few miles. New friction material needs to bed against the rotor before it bites the way it should, so leave extra room and avoid one hard stop from speed on the way home. If the pedal feels soft or travels further than it did before, stop and work out why rather than driving on it.
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.
