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Pelican Technical Article:

Front Brake Pad Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$40

Talent:

**

Tools:

12mm socket, flathead screw driver

Applicable Models:

Mercedes-Benz W203 (2001-07)

Parts Required:

New pads

Hot Tip:

Pre-soak rusted bolts in penetrant oil

Performance Gain:

Car stops better

Complementary Modification:

Replace Rotor or disk

Check out some other projects from our technical library:

Replacing your brake pads is one of the easiest jobs to perform on your Mercedes. In general, you should inspect your brake pads about every 25,000 miles, and replace them if the material lining of the pad is worn down enough to trigger the pad replacement sensor or there is less than a quarter inch of material on the pad. In reality, most people don't inspect their pads very often, and usually wait until they see the little brake-warning lamp appear on the dashboard. It's a wise idea to replace the pads, and inspect your discs as soon as you see that warning lamp go on.

If you ignore the warning lamp, you may indeed get to the point of metal on metal contact, where the metal backing of the pads are contacting the brake discs. Using the brakes during this condition will not only give you inadequate braking, but will also begin to wear grooves in your brake discs. Once the discs are grooved, they are damaged, and there is often no way to repair them. Resurfacing will sometimes work, but often the groove cut will be deeper than is allowed by OEM specifications. The smart thing to do is to avoid this problem replace your pads right away.

The first step is to jack up the car and remove the road wheel. This will expose the brake caliper that presses the pads against the disc.

To replace the front brake pads on the Mercedes W203, you need to remove the caliper.

Begin by unplugging the wear sensor attached to the pad. It simply pulls out from where it is attached to the caliper.

Use a large screw driver between the pad and disk to compress the caliper piston back into the caliper. This will make removing the caliper from the disk easier, especially if the risks are worn.

Next remove the two 12mm bolts holding the caliper to its mount.

After the guide bolts have been removed, you should be able to simply lift the caliper off of its mount. Suspend the caliper using some zip-ties or rope until you are ready to work with it again. Never let the caliper hang from its rubber hose (this can damage the brake line)

Once you have the caliper removed, inspect the inside of it. Make sure that the dust boots and the clamping rings inside the caliper are not ripped or damaged. If they are, then the caliper may need to be rebuilt. At this point, you should inspect the brake discs carefully. Using a micrometer, take a measurement of the disc thickness. If the disc is worn beyond its specifications, then it's time to replace it along with the one on the other side (see Project on replacing brake discs).

To install the new brake pads, you will need to take a C-clamp and old brake pad to push the caliper piston back into the caliper. This is because the new pads are going to be quite a bit thicker than the old worn-out ones, and the piston is set in the old pad's position. Push back the piston using the clamp, being careful not to use too much force. Using a screwdriver here can accidentally damage the dust boot and seals inside the caliper, and is not recommended.

Be aware that as you push back the pistons in the calipers, you will cause the level of the brake reservoir to rise. Make sure that you don't have too much fluid in your reservoir. If the level is high, you may have to siphon out a bit from the reservoir to prevent it from overflowing.

Move to the caliper mount bracket and remove the two brake pads from their mounts.

Use a pair of needlenose pliers to pull out the old sensor if you plan to re-use it. With a new sensor, simply push it into the hole on the pad as seen here.

Apply some anti squeal to the back of the new pads and install them in there brackets on the caliper mount. With the piston compressed into the caliper reinstall the caliper over the pads and back onto the bracket. Install the guide bolts and torque to spec. Once the caliper is mounted to the bracket, plug the sensor back into the harness.

When finished with both sides, press on the brake pedal repeatedly to make sure that the pads and the pistons seat properly. Also make sure that you top off the master cylinder brake fluid reservoir if necessary. Brake pads typically take between 100 and 200 miles to completely break in. It's typical for braking performance to suffer slightly as the pads begin their wear-in period. Make sure that you avoid any heavy braking or emergency maneuvers during this period.

The first step is to jack up the car and remove the road wheel.
Figure 1

The first step is to jack up the car and remove the road wheel. This will expose the brake caliper (red arrow) that presses the pads against the disc (yellow arrow) .

Begin by unplugging the wear sensor attached to the pad.
Figure 2

Begin by unplugging the wear sensor attached to the pad. It simply pulls out from where it is attached to the caliper (yellow arrow) .

Use a large screw driver between the pad and disk (yellow arrow) to compress the caliper piston back into the caliper.
Figure 3

Use a large screw driver between the pad and disk (yellow arrow) to compress the caliper piston back into the caliper. This will make removing the caliper from the disk easier, especially if the risks are worn.

Next remove the two 12mm guide bolts (yellow arrows) holding the caliper to its mount.
Figure 4

Next remove the two 12mm guide bolts (yellow arrows) holding the caliper to its mount.

After the guide bolts have been removed, you should be able to simply lift the caliper off of its mount.
Figure 5

After the guide bolts have been removed, you should be able to simply lift the caliper off of its mount.

Suspend the caliper using some zip-ties or rope (yellow arrow) until you are ready to work with it again.
Figure 6

Suspend the caliper using some zip-ties or rope (yellow arrow) until you are ready to work with it again. Never let the caliper hang from its rubber hose (this can damage the brake line).Once you have the caliper removed, inspect the inside of it. Make sure that the dust boots and the clamping rings inside the caliper (red arrow) are not ripped or damaged. If they are, then the caliper may need to be rebuilt.

To install the new brake pads, you will need to take a C-clamp and old brake pad (yellow arrow) to push the caliper piston back into the caliper.
Figure 7

To install the new brake pads, you will need to take a C-clamp and old brake pad (yellow arrow) to push the caliper piston back into the caliper. This is because the new pads are going to be quite a bit thicker than the old worn-out ones, and the piston is set in the old pad's position. Push back the piston using the clamp, being careful not to use too much force.

Be aware that as you push back the pistons in the calipers, you will cause the level of the brake reservoir to rise.
Figure 8

Be aware that as you push back the pistons in the calipers, you will cause the level of the brake reservoir to rise. Make sure that you don't have too much fluid in your reservoir. If the level is high, you may have to siphon out a bit from the reservoir to prevent it from overflowing.

Move to the caliper mounting bracket and remove the two brake pads from their mounts (yellow arrows).
Figure 9

Move to the caliper mounting bracket and remove the two brake pads from their mounts (yellow arrows).

Use a flathead screw driver to carefully push out the old sensor (yellow arrow) if you plan to re-use it.
Figure 10

Use a flathead screw driver to carefully push out the old sensor (yellow arrow) if you plan to re-use it. With a new sensor, simply push it into the hole on the pad.

Apply some anti squeal to the back of the new pads and install them in there brackets on the caliper mount.
Figure 11

Apply some anti squeal to the back of the new pads and install them in there brackets on the caliper mount.

With the piston compressed into the caliper reinstall the caliper over the pads and back onto the bracket.
Figure 12

With the piston compressed into the caliper reinstall the caliper over the pads and back onto the bracket. Install the guide bolts and torque to spec. Once the caliper is mounted to the bracket, plug the sensor back into the harness.

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Comments and Suggestions:
Jan Comments: My husband followed your directions and successfully changed the brakes onhis BMW and my Mercedes. You just saved us a lot of money.
April 19, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
rock Comments: love my Mercedes-benz
March 29, 2014
  Followup from the Pelican Staff: Great! - Nick at Pelican Parts  

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