Mercedes W123 Brake Caliper, Front Replacement


  1. Mercedes W123 Brake Caliper, Front Replacement, Drain the brake fluid: crwdns2935265:01crwdnd2935265:01crwdnd2935265:02crwdne2935265:0 Mercedes W123 Brake Caliper, Front Replacement, Drain the brake fluid: crwdns2935265:01crwdnd2935265:02crwdnd2935265:02crwdne2935265:0
    • You will need to remove your wheels before you start.

    • Before beginning on removal of the calipers you should drain the brake fluid from them.

    • This is done through the bleed screw on each caliper.

    • Loosen this and let it drain in to a proper drain pan.

  2. Mercedes W123 Brake Caliper, Front Replacement, Remove the sensors: crwdns2935265:02crwdnd2935265:01crwdnd2935265:01crwdne2935265:0
    • Several items need to be disconnected from the front caliper before it can be removed.

    • The first is the wiring harness for the brake pad sensors.

    • Use a 10mm wrench to remove the bolt and washer holding it to the caliper.

    • Then unplug the ends of the sensors from the harness.

    • Let the harness hang up and out of the way.

  3. Mercedes W123 Brake Caliper, Front Replacement, Remove the rubber hoses: crwdns2935265:03crwdnd2935265:01crwdnd2935265:02crwdne2935265:0 Mercedes W123 Brake Caliper, Front Replacement, Remove the rubber hoses: crwdns2935265:03crwdnd2935265:02crwdnd2935265:02crwdne2935265:0
    • Next you will need to remove the soft rubber brake hoses.

    • You will have to start by disconnecting the rubber hose from the hard line connection up inside the fender well. Then you can loosen it from the caliper and remove the line. This takes a 14mm wrench for the soft hose and an 11 mm wrench for the brake line.

    • For more information and tips on removing these lines, [crwdns2936915:0crwdne2936915:0]

    • Speaking of the rubber hoses, this is a great time to replace them with new parts if they show signs of age since they are already off of the car.

  4. Mercedes W123 Brake Caliper, Front Replacement, Remove the calipers: crwdns2935265:04crwdnd2935265:01crwdnd2935265:02crwdne2935265:0 Mercedes W123 Brake Caliper, Front Replacement, Remove the calipers: crwdns2935265:04crwdnd2935265:02crwdnd2935265:02crwdne2935265:0
    • Next use a large ratchet wrench with a 19mm socket to remove the two bolts that hold the caliper to the steering knuckle.

    • These bolts are in very tight, and had thread locker on them from the factory, so you may need a very long wrench or a breaker bar in order to get enough leverage to remove these two bolts.

    • Hold on to the caliper as you remove the second of the two bolts so it doesn't fall when you remove the bolt.

  5. Mercedes W123 Brake Caliper, Front Replacement, Prepare the caliper bolts: crwdns2935265:05crwdnd2935265:01crwdnd2935265:02crwdne2935265:0 Mercedes W123 Brake Caliper, Front Replacement, Prepare the caliper bolts: crwdns2935265:05crwdnd2935265:02crwdnd2935265:02crwdne2935265:0
    • After you have completed your work on the caliper, such as removing the old pads, and cleaning them up, they can be re-installed. Or, if you have new calipers, this is the time to install them.

    • Before installing the caliper bolts be sure to apply some thread locker to them. Use the blue thread locker than can be removed with hand tools, not the red thread locker as that needs heat to remove.

    • Hold the caliper up on the rotor and line the holes in the caliper up with the bolt holes in the steering knuckle. Get the first bolt started by hand.

    • Then, start the second bolt by hand as well. Doing so helps ensure they do not become cross-threaded.

  6. Mercedes W123 Brake Caliper, Front Replacement: crwdns2935265:06crwdnd2935265:01crwdnd2935265:01crwdne2935265:0
    • Then tighten the bolts down until they seat against the caliper. Do not tighten them all the way down with the normal ratchet wrench.

  7. Mercedes W123 Brake Caliper, Front Replacement, Torque the bolts to spec: crwdns2935265:07crwdnd2935265:01crwdnd2935265:01crwdne2935265:0
    • Switch your 19mm socket to a large 1/2 inch drive torque wrench. Torque both of the caliper bolts down to 115 nm/85 lb-ft.

  8. Mercedes W123 Brake Caliper, Front Replacement, Re-install sensors: crwdns2935265:08crwdnd2935265:01crwdnd2935265:01crwdne2935265:0
    • Re-attach the sensor harness and insert the sensors back in to the connectors on the harness.

  9. Mercedes W123 Brake Caliper, Front Replacement, Re-attach brake hoses: crwdns2935265:09crwdnd2935265:01crwdnd2935265:01crwdne2935265:0
    • Re-attach the brake hoses, starting at the calipers and then attaching them to the hard lines.

    • Before you drive the car you must bleed your brakes of air since you opened up the system. Never drive the car without bleeding after you've worked on the lines, or calipers. [crwdns2936915:0crwdne2936915:0]

  10. Mercedes W123 Brake Caliper, Front Replacement, Take note!: crwdns2935265:010crwdnd2935265:01crwdnd2935265:01crwdne2935265:0
    • An important note - if you are removing and replacing the front and rear calipers at the same time be sure to keep the front and rear bolts separate.

    • This is because they are different designs. While you can use the rear bolts on the front calipers, the front bolts will not fit on the rear calipers.

    • Front bolt, with a shoulder

    • Rear bolt, no shoulder, all thread


When finished be sure to take a test drive before going on a long trip.


Nicolas Siemsen


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Master Techs crwdns2935289:0Master Techscrwdne2935289:0





You'll find it wise to use a toothbrush sized wire brush to clean the calipers where the pads go while it's all apart .


vwnate1 - crwdns2934203:0crwdne2934203:0

Thanks for the comment. You'll note I mention cleaning the calipers in the brake pad replacement guide. This guide is just to show the steps for removing and replacing the caliper itself.

Nicolas Siemsen -

Thank you for thus DETAILED information !! My manual never accurately showed me how… Thanks again.. Mike in Jax FL…

mw090958 - crwdns2934203:0crwdne2934203:0



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