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Rear Brake Caliper Replacement
 
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Pelican Technical Article:

Rear Brake Caliper Replacement

Steve Vernon

Time:

3 hours3 hrs

Tab:

$60 to $700

Talent:

**

Tools:

19mm, breaker bar, 14mm, 11mm flared nut wrench, pliers, catch bottle, hose

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Caliper(s)

Hot Tip:

You must bleed the brake system after installation

Performance Gain:

Car stops better

Complementary Modification:

Bleed the brake system

With proper maintenance, your braking system calipers should last a very long time. Besides being damaged in an accident or by some form of road debris, calipers usually start to fail around the seals and dust boots. If you see fluid starting to leak out from around the dust boot or the dust boot is torn and the piston is starting to get corrosion on it, it is time to change your calipers right away. Never drive your vehicle with a leaking brake piston.

Safely jack up and support the front of the vehicle and remove the front wheels. Please see our article on safely lifting and supporting your Mercedes 123.

Since you are going to be opening the system to air, you absolutely need to completely bleed the brake system before you operate the vehicle. While some fluid is going to leak out, one of the things you can do to help minimize the loss is to press the brake pedal down an inch or two and use a piece of wood between the seat and pedal to hold the pedal in this position. This will help to minimize the loss of fluid.

Once you install the new calipers you MUST bleed the system; do not attempt to drive the car without first bleeding the system.

To replace the front caliper you will first need to remove the brake pads (red arrows); please see our article on brake pad removal for additional assistance.
Figure 1

To replace the front caliper you will first need to remove the brake pads (red arrows); please see our article on brake pad removal for additional assistance.

There is a flexible brake line (red arrow) from the hard line on the chassis (yellow arrow) to the brake caliper.
Figure 2

There is a flexible brake line (red arrow) from the hard line on the chassis (yellow arrow) to the brake caliper. If you are NOT replacing this line, you will need to loosen the line on the caliper first then remove the caliper to remove the line. The end of the line where it joins the hard line is fixed and you cannot spin the line off the caliper while it is attached to it.

Whenever working with brake lines always make sure to use the proper too--which is a flared nut wrench.
Figure 3

Whenever working with brake lines always make sure to use the proper too--which is a flared nut wrench. This wrench is designed to grasp the fitting on 5 sides and help you avoid the time consuming and costly mistake of stripping the line fitting.

Use a 14mm flared nut wrench and break loose the brake line to caliper (red arrow).
Figure 4

Use a 14mm flared nut wrench and break loose the brake line to caliper (red arrow).

Next use a 19mm socket and depending on who installed the caliper last you might need a breaker bar.
Figure 5

Next use a 19mm socket and depending on who installed the caliper last you might need a breaker bar. Remove the two bolts making sure to support the caliper while removing the last bolt.

The bolts are micro-encapsulated (red arrow) and while Mercedes considers these bolts single use if you are going to reuse them make sure to clean up the threads and use a small amount of Blue Loctite when reinstalling.
Figure 6

The bolts are micro-encapsulated (red arrow) and while Mercedes considers these bolts single use if you are going to reuse them make sure to clean up the threads and use a small amount of Blue Loctite when reinstalling.

With the caliper removed from the hub you can spin it off of the brake line (red arrow) and you will need to install the new caliper in the same manner.
Figure 7

With the caliper removed from the hub you can spin it off of the brake line (red arrow) and you will need to install the new caliper in the same manner.

Most calipers are sold with a core fee which means you will be needing to return your old calipers.
Figure 8

Most calipers are sold with a core fee which means you will be needing to return your old calipers. Most new calipers will come with a bleed screw and cap; check yours before sending the old caliper back and transfer over the cap and screw to your new ones if they didn't come equipped with them (red arrow).

Installation is the reverse of removal and remember you must bleed your brakes before attempting to drive the vehicle.
Figure 9

Installation is the reverse of removal and remember you must bleed your brakes before attempting to drive the vehicle. Please see our article on brake bleeding including the Motive Power Bleeder that makes it quick and simple

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