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Front Brake Pad Replacement
 
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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

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:
shot Comments: Nick, I do not have a pressurized air system. I do have a portable small compressor that I use for my lawn tractor tire. Not sure it will generate 100 PSI to facilitate the use of a vacuum system. Also, not sure about the adaptors for using the portable air compressor. I only have the tire inter tube connection. My guess is that the vacuum sys. has connections for the shop compressor. How does installing a check valve on the bleeder nipple work? I know it would be more work but if I can not use the vacuum sys. would the check valve work OK?
April 27, 2017
  Followup from the Pelican Staff: It prevents air from traveling back into the system.

The vacuum bleeders come with instructions on how to connect. Every one is different. - Nick at Pelican Parts
 
shot Comments: How to bleed the brakes on my 380 SE?
April 26, 2017
  Followup from the Pelican Staff: Your brake system is a hydraulic system. As you step on your brakes a piston in the master cylinder compresses brake fluid. This brake fluid is forced through the brake lines to the caliper to act on the brake pads. If you have a leak in your brake system air can get in. Air in the brake system reduces the pressure that the brake system can generate. As you step on the brake pedal the brake fluid compresses the air in the brake lines instead of increasing the pressure of the brake fluid. By bleeding the brakes you can remove the air, moisture and any other contaminants in the hydraulic system. Also, Mercedes Benz recommends the brake fluid gets flushed at specific intervals. Seals in the brake system wear out and these particulates can accumulate in the master cylinder, calipers and ABS brake systems causing components to stick and possibly fail. In this tech article we will go over all the steps to bleed your brake system.

Mercedes Benz recommends you replace your brake fluid every 2 years.

Now there are a few ways you can bleed your brake system depending on the level of equipment you have. The best way and fastest way to bleed the brakes are pressure bleeders. These pressure bleeders are filled with brake fluid. You add air to a bladder on the other side of the brake fluid diaphragm and this pressurizes the brake fluid. You attach this pressurized brake fluid, through adapters, to the brake master cylinder fluid reservoir. Now pressurized brake fluid is being applied to the brake system of the car. All you have to do is open the bleeder screw and old brake fluid will be forced out. Keep the line open until you see clean brake fluid coming out of the bleeder screw without any air bubbles in it. There are two types of these pressure bleeders; one uses shop air to generate pressure and one has a manual pump built into it. We have an air powered pressure bleeder and that is what we are going to show you.
A second type of powered bleeding system is the vacuum type bleeder. Here you attach a vacuum pump to the bleeder screw on the caliper. There are two types of vacuum generating bleeder systems. One uses compressed shop air if you have a compressor the other has a manual pump that generates the vacuum. Make sure the reservoir is full and apply a vacuum to the bleeder screw then open the screw. The tool will draw the old brake fluid out and it will be replaced with the new fluid you put in the master cylinder reservoir.

Finally the last method requires a helper. The helper will pump on the brake system and finally hold it down to generate the necessary brake system pressure. While they are pushing the pedal to the floor you open one of the bleeder screws. Fluid and air will come out and the brake pedal will sink to the floor. When the brake pedal hits the floor have them hold it there until you close the bleeder screw. Have your helper release the brake pedal and pump the pedal up 2 to 3 times again. Open the bleeder screw again and repeat this step at the same brake caliper several times until the brake fluid runs clear and is free of air bubbles. Mercedes Benz recommends you start at the right side rear wheel, followed by the left side rear wheel, followed by the right side front wheel and finally the left side front wheel. Make sure the brake fluid reservoir is topped off each time you switch to bleed a different wheel.
Mercedes Benz recommends you exchange your brake fluid every two years.
In order to bleed the brakes you should lift and support your vehicle. It will be more difficult on the ground where you have to reach behind the wheels while you open and close the brake caliper bleeder screw. It is possible but makes the job more difficult. - Nick at Pelican Parts
 
EricExperience Comments: This instruction does not apply to a 05 203. no tools are required except a 4 inch nail to push out the pins. just press the flat spring to take the presser of the pins then push the pins out.
September 4, 2016
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it. I will have the article updated.
- Nick at Pelican Parts
 
BOBBY Comments: TOO COMPLICATED.NONEED TO REMOVE CALIPERS. JUST TAP OUT PINS AND REPACE PADS AND WEAR SENSOR.
June 1, 2016
  Followup from the Pelican Staff: These calipers are bolted on, the fasteners have to be removed. - Nick at Pelican Parts  
GP Comments: What are the torque specs for the tightening the bracket to the base 18mm bolt? And the caliber to the bracket 12mm bolt? Thank you so much in advance.
April 11, 2016
  Followup from the Pelican Staff: I don’t have that info.


I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
ADY Comments: Hi i find your website very helpful ,when working on my W203 MERCEDES

Many thanks
March 2, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Long Islander Comments: Do these instructions apply to a W211 4matic? My calipers look a bit different - they have a visible wire clip on the caliper.
February 29, 2016
  Followup from the Pelican Staff: Applies to Mercedes-Benz W203 (2001-07) - Nick at Pelican Parts  
johninftl Comments: This article made replacing from brakes a breeze.

Thanks so much!!
February 16, 2015
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help. - Nick at Pelican Parts  
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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Page last updated: Tue 10/17/2017 02:36:38 AM