2013-2016 Mercedes-Benz C300 Brake Caliper Problems and Replacement

By Core Brake Parts Tech Team — Circleville, OH warehouse

A failing brake caliper on a 2013-2016 Mercedes-Benz C300 usually shows up as a pull to one side, a hot or smelly wheel after a drive, or one pad worn far thinner than its partner. Most of the time the cause is a sticking guide pin or a piston that no longer retracts, not a dramatic leak. The fix depends on which generation you own: the 2013-2014 car is the W204 with a foot-pedal parking brake, while the 2015-2016 car is the W205 with an electric parking brake that changes how you service the rear calipers.

Two Generations, Two Rear Brake Designs

This model-year span covers two different C-Class platforms, and that matters the moment you pick up a wrench.

The 2014 C-Class operator's manual tells the driver to depress the parking brake pedal firmly to apply it and to pull the release handle to let it off. The 2016 manual instead describes an electric parking brake that applies itself automatically when the car is in P and the engine is switched off, and that runs self-tests while the car sits. That self-test is why a W205 owner may hear a short whir from the rear wheels after parking. It is normal, and it is also why you cannot simply lever a W205 rear piston back like you would on an older car.

Symptoms of a Bad Caliper on the C300

• Pulling while braking. A caliper that clamps harder, or later, than its partner pulls the car toward the stronger side.
• Heat and odor at one wheel. A dragging caliper keeps the pad on the rotor, so that wheel runs much hotter than the others and may smell burnt after a drive.
• Uneven pad wear. On a floating caliper the inner pad normally wears slightly faster than the outer. If the inner pad is nearly gone while the outer looks fresh, or one pad is worn into a taper, a guide pin is sticking.
• Brake fluid on the wheel or tire. A leaking piston seal leaves a wet, oily film on the inside of the wheel and the caliper body.
• Low fluid warning. The owner's manual notes that the red brake warning lamp with a warning tone can mean low brake fluid, caused either by pad wear or by leaking lines. Both deserve an immediate inspection.
• Parking brake messages (W205). A rear caliper with a failed actuator or wiring fault can trigger a parking brake warning, or leave the brake unable to apply or release.

To diagnose it yourself, drive a few miles with light braking, then carefully compare hub temperatures by holding your hand near each wheel. One wheel noticeably hotter than the other on the same axle points to that caliper. Then pull the wheel and compare inner and outer pad thickness.

What Actually Causes C300 Caliper Problems

Seized guide pins

On a floating caliper, the common design on standard-brake cars, a piston on the inboard side pushes the inner pad and the caliper body slides on guide pins to pull the outer pad in. When a pin boot tears, water and road grime get in, the pin corrodes, and the caliper stops sliding. The inner pad then does most or all of the work. This is the most common "bad caliper" on these cars, and it is often cured by cleaning or replacing the pins and boots rather than the whole caliper.

Sticking pistons

If the dust boot around the piston splits, moisture reaches the piston and seal. The piston surface pits, the seal can no longer pull it back, and the pad drags. A pitted or seized piston means a replacement caliper.

Old brake fluid

Mercedes-Benz warns in the owner's manual that brake fluid constantly absorbs moisture from the air, which lowers its boiling point. That same moisture corrodes caliper bores and pistons from the inside. The manual points owners to the Maintenance Booklet for the change interval and asks that fluid be replaced on that schedule. Skipping fluid changes is one of the quiet reasons calipers fail early.

Electric parking brake faults (W205 rear)

On the 2015-2016 car the rear caliper carries an electric actuator. The manual notes that the system depends on on-board voltage, and that a weak battery or a system malfunction can prevent the brake from applying or releasing. Test the battery before condemning a rear caliper that will not release.

The Fix: Replacing a Caliper on a C300

If the pins cleaned up and the pistons move freely, new pads, rotors and hardware may be all the car needs. If the piston is seized, the bore leaks, or the pins are corroded into the bracket, replace the caliper. Browse replacement brake calipers and confirm the part by your exact model year and brake package, since sport packages and the two generations use different parts.

1. W205 only: put the rear calipers in fitting position first. A widely followed W205 procedure is: press the start button once to the first key position, hold the phone and OK buttons on the steering wheel for about five seconds, choose Brake Pad Replacement, and press OK. You will hear the parking brake motors retract. Do not force a W205 rear piston back without doing this.
2. Loosen the brake hose fitting, remove the caliper, and never let a caliper hang by its rubber hose.
3. Clean the bracket and pad abutments, install new hardware, and lubricate guide pins with a brake-specific synthetic lubricant. Petroleum grease swells rubber boots and causes the same sticking you are trying to fix.
4. Torque every fastener to the factory specification. For the W205 rear caliper bracket bolts, the procedure we reviewed lists 60 Nm (44 ft-lbs) plus an additional 45 degrees. Use the factory service manual for the front caliper and for all W204 fasteners.
5. Bleed the brakes with fluid approved to MB-Approval 331.0, then pump the pedal until it is firm before moving the car. On a W205, take the parking brake out of fitting position before driving and confirm it applies and releases normally.

What to Replace at the Same Time

A failed caliper usually cooked the pads and rotor on that wheel. Mercedes-Benz's owner's manual says to always replace all brake discs and pads on an axle at the same time, and to always install new pads when replacing discs. Replace calipers in pairs on the same axle when they are the same age; if one side seized, the other is rarely far behind, and matched calipers keep the car from pulling.

• 2013-2014 W204 C300 front rotors: EBC Ultimax OE-style front rotor set for the W204 C300.
• 2016 W205 C300 rear rotors: DBA Street Series T2 slotted rear rotor for the W205 C300.
• W205 C300 with the AMG Sport Package, rear pads: EBC Redstuff ceramic low-dust rear pads for daily driving, or EBC Yellowstuff street and track rear pads for harder use.
• New brake hardware kits (clips and pins) and a new pad wear sensor if the old one was worn through.

More options are in our brake pads and brake rotors collections.

How Hard Is the Job?

A front caliper swap on either generation is a moderate DIY job for someone who has done a pad and rotor change: basic hand tools, a torque wrench, a line wrench for the hose, and a bleeder setup. The W204 rear is similar. The W205 rear adds the fitting-position step, and if the car will not enter fitting position because of a fault, you will need a scan tool that can command the parking brake or a shop that has one. Brake work is safety-critical; the owner's manual recommends having it done at a qualified specialist workshop, so if you are unsure about bleeding or torque, let a shop handle it. New pads and rotors also need several hundred kilometers of driving to reach full braking effect, according to the manual, so allow extra stopping distance at first.

Frequently Asked Questions

Is my 2015 or 2016 C300 a W205 with an electric parking brake?

Yes. The US 2015 and 2016 C-Class sedan manuals describe an electric parking brake. The 2013-2014 C300 is the W204 with a foot-operated parking brake pedal.

Can I just rebuild or clean a sticking caliper instead of replacing it?

If only the guide pins are sticking, cleaning or replacing the pins and boots with fresh brake lubricant often fixes it. If the piston is pitted, seized or leaking, replace the caliper.

Do I have to replace both calipers?

It is not mandatory, but calipers of the same age on the same axle tend to fail close together, and a matched pair keeps braking balanced. Pads and rotors should always be replaced on both sides of the axle.

What brake fluid does the C300 use?

Mercedes-Benz specifies brake fluid approved to MB-Approval 331.0. Check the container for that approval before you bleed the system.

Why will my W205 rear brake piston not push back?

The electric parking brake mechanism is holding it. Put the calipers in fitting position through the instrument cluster menu first, or use a scan tool that can retract the parking brake.

Are there any recalls on C300 brake calipers?

We did not find a C300 caliper recall for these years, but recalls are issued by VIN. Check your car at the Mercedes-Benz USA recall page or NHTSA before paying for a repair.

Sources

1. Mercedes-Benz USA 2016 C-Class Sedan Operator's Manual - electric parking brake operation and voltage dependence, brake fluid moisture warning and MB-Approval 331.0, replace pads and discs per axle, low brake fluid warning
2. Mercedes-Benz USA 2014 C-Class Sedan Operator's Manual - foot-operated parking brake pedal and release handle on the W204
3. FCP Euro: W205 rear brake pad and rotor replacement - fitting position menu steps, rear caliper bracket torque, never hang a caliper by its hose
4. CARDONE: Brake caliper function and common failures - how caliper pistons apply and retract, follow OE guidelines when replacing
5. Free ASE Study Guides: Sticking caliper guide pins - uneven and tapered pad wear from seized pins, torn boots, brake-specific synthetic lubricant