2013-2016 Mercedes-Benz C300 Parking Brake Problems and Adjustment

By Core Brake Parts Tech Team — Circleville, OH warehouse

Parking brake trouble on a 2013-2016 Mercedes-Benz C300 depends on which generation you have. The 2013-2014 C300 (W204) uses a foot-pedal parking brake that applies small cable-operated shoes inside the rear rotor hat, and those shoes are adjusted by hand. The 2015-2016 C300 (W205) uses an electric parking brake with no manual adjustment at all; its problems are almost always voltage, warning-message or rear-caliper related.

Which Parking Brake Does Your C300 Have?

Mercedes changed the system when the C-Class moved from the W204 to the W205 body, so the first step in any diagnosis is knowing which one is in your driveway.

The 2014 owner's manual describes the W204 procedure: depress the parking brake firmly to apply it, and to release it, hold the service brake pedal down and pull the release handle. The 2015 and 2016 manuals describe the W205 electric handle instead: push to apply, pull to release, with the ignition on.

2013-2014 C300 (W204): Common Problems and Adjustment

Symptoms

• The car creeps or rolls on a hill with the pedal fully applied. The shoes are worn, glazed, contaminated, or the star-wheel adjusters have backed off.
• The pedal travels much further than it used to. Shoe clearance has grown with wear, or the cables have stretched.
• Grinding or a faint scrape from the rear after a brake job. The shoes were set too tight, or broken shoe hardware is rubbing the drum.
• A warning tone and the "Release Park. Brake" message while driving. Per the owner's manual, this means the parking brake is still applied. If you released it and the message persists, the release mechanism or pedal switch needs attention.

Why the shoes lose their grip

Drum-in-hat shoes are not supposed to wear much, because they only hold a stopped car. They wear out when the car is driven with the brake partly on, when the parking brake is used to stop the car, or simply from years of rust building on the inside of the rotor hat. The 2014 manual warns that stopping with the parking brake gives a much longer stopping distance and can lock the rear wheels, so it should only be used that way if the service brakes fail. Moisture and rust can also make the shoes stick to the drum after the car sits.

How adjustment works

There are two adjustments, and the order matters. The trade guidance in Brake and Front End is clear: set the shoe-to-drum clearance at the wheels first, then take up slack in the cable. The cable adjustment is only meant to remove slack, not to make up for worn shoes.

1. Chock the front wheels, release the parking brake, and raise and support the rear of the car. Remove the rear wheels.
2. Turn the rotor until a lug bolt hole lines up with the star-wheel adjuster, which you can see through that hole with a flashlight.
3. With a screwdriver or brake spoon, turn the star wheel until the shoes drag and the rotor will not turn by hand.
4. Back the adjuster off until the rotor turns freely, with at most a faint, even rub. Repeat on the other side.
5. Apply and release the pedal several times to seat the shoes, then check that the brake holds at a reasonable pedal height. Only if there is still excess travel should you adjust cable tension at the equalizer.

Brake and Front End cautions that backing off an adjuster purely by feel can cause trouble, because shoes can swell with moisture or heat and start to drag once hot. Recheck for drag after a short drive. If you cannot make the brake hold after adjustment, the shoes are done and must be replaced.

2015-2016 C300 (W205): Electric Parking Brake Problems

The electric parking brake (EPB) has no cable or shoes to adjust. Its common complaints come from the electronics and the rear calipers.

Low battery voltage

The 2015 owner's manual states that the EPB depends on the on-board voltage. With low voltage or a system fault, it may not apply, and an applied brake may not release. A "Parking Brake Inoperative" message with the yellow warning lamp is listed as a malfunction that can be caused by overvoltage or undervoltage, and the manual's remedy is to remove the cause, such as charging the battery or restarting the engine. A weak or aging battery is the first thing to test on any W205 with EPB warnings.

Warning lamps and messages

• Red parking brake indicator lit: normal when the brake is applied.
• Yellow EPB warning lamp plus the red lamp: the system reports a malfunction. The manual says to switch the ignition off and back on, then try to release the brake manually or automatically. If it still will not release, do not drive; have the system diagnosed.
• Red lamp flashing for about ten seconds after applying or releasing, then yellow lamp on: another malfunction condition. If the brake will not apply, shift to P and secure the car.

Automatic apply and release surprises

Many "it will not release" complaints are really the automatic logic working as designed. The EPB releases automatically when the engine is running, the transmission is in D or R, the seat belt is fastened and you press the accelerator. If the belt is not fastened, the driver's door must be closed and you must have shifted out of P or already driven faster than 2 mph (3 km/h). In R, the trunk lid must also be closed. It can also apply by itself when DISTRONIC PLUS, the HOLD function or Active Parking Assist is holding the car and the engine is switched off or the driver's door opens with the belt unbuckled.

Normal noises

The manual notes that the EPB runs a self-test at regular intervals while the engine is off, and the whirring you hear is normal. A grinding or clicking noise while applying, or a brake that applies on only one side, points to a failing caliper motor or a seized caliper.

Rear Brake Service on an EPB Car

On the W205, the parking brake motor pushes on the same piston the hydraulic system uses. That means you cannot simply press the piston back to fit new rear pads. The EPB must first be put into its service position with a capable scan tool, then returned to normal and calibrated after the new pads are in. Forcing the piston back with the motor still applied can damage the actuator. Mercedes also warns that the ignition must be off if the EPB is tested on a brake dynamometer, because automatic braking can damage the brake system.

When the rear pads are worn to the indicator, replace them as an axle set and check the rotors for minimum thickness, scoring and a lip at the edge. For 2015 and newer C300 sedans with the AMG Sport Package, we carry EBC Redstuff low-dust ceramic rear pads for the W205 C300 and the more aggressive EBC Yellowstuff street and track rear pads. For 2016 and newer models, the DBA Street Series T2 slotted rear rotor is a direct replacement.

What to Replace Together and How Hard the Job Is

On a 2013-2014 C300, the parking brake shoes live inside the rear rotor, so the best time to replace them is when the rear rotors come off anyway. The job means removing the caliper and rotor, unhooking the shoe springs and cable, and installing new shoes and hardware. New springs and adjusters are worth fitting with new shoes, because old springs lose tension and rusted adjusters will not turn. Clean rust out of the drum surface inside the hat before installing a new rotor, and adjust the shoes before the wheel goes back on. For a home mechanic with basic tools this is a moderate job; the spring work is the fiddly part.

On a 2015-2016 C300, pads and rotors are the routine parts, and the EPB caliper motor is the part that eventually fails. The job is moderate if you own a scan tool that can retract the EPB, and a shop job if you do not. The 2015 manual itself recommends having pads installed and brake fluid replaced at a qualified specialist workshop.

Whichever generation you drive, front pads and rotors usually wear faster than the rears. For 2013-2014 models, the EBC Ultimax OE-style front rotor set for the W204 C300 is a direct OE-style replacement. You can browse more in our brake rotors, brake pads and brake hardware kits collections.

Frequently Asked Questions

Can I adjust the parking brake on a 2015 or 2016 C300?

No. The W205 electric parking brake is self-adjusting and has no cable or star wheel. If it does not hold or will not release, test the battery first, then have the EPB system scanned for fault codes.

Why does my 2013 or 2014 C300 roll on a hill with the parking brake on?

The rear drum-in-hat shoes are usually worn, rusted or out of adjustment. Adjust the shoes at the star wheel first, then check cable slack. If it still will not hold, the shoes need replacing.

My C300 electric parking brake will not release. What should I do?

Fasten your seat belt, close the doors, start the engine, and try releasing it with the handle. The owner's manual also says to switch the ignition off and on, then try manual or automatic release. If it still will not release, do not drive; a low battery or a caliper motor fault is the likely cause.

Can I replace the rear pads on a W205 C300 without a scan tool?

It is not recommended. The EPB motor must be moved to its service position before the piston is pushed back, then recalibrated afterwards. Forcing it can damage the actuator.

Do the brake lights come on if I stop with the parking brake?

On the 2013-2014 C300, the owner's manual says the brake lamps do not light when you brake with the parking brake. On the 2015-2016 EPB car, holding the handle in an emergency brakes the car with a warning tone and a flashing red lamp.

Sources

1. Mercedes-Benz USA - 2014 C-Class Sedan Operator's Manual - W204 foot-pedal parking brake apply and release, "Release Park. Brake" message, brake lamps do not light when stopping with the parking brake
2. Mercedes-Benz USA - 2015 C-Class Sedan Operator's Manual - electric parking brake operation, voltage dependence, automatic apply and release conditions, warning messages, self-test noise, dynamometer caution
3. Mercedes-Benz USA - 2016 C-Class Sedan Operator's Manual - confirms the electric parking brake on the 2016 C-Class
4. Brake and Front End - Adjusting Parking Brakes - drum-in-hat star-wheel adjustment, adjusting shoes before cables, cautions about adjusting by feel
5. Wilwood - How to Adjust the Internal Drum Parking Brake - how an internal drum parking brake works on the inside of the rotor hat and star-wheel adjustment steps