Mercedes-Benz C-Class C63 AMG: Common Problems

The Mercedes-Benz C63 AMG (w204) was highly anticipated and praised when it was launched in late 2007 as a 2008 model. Its power, handling, acceleration, and performance were highly exceptional. But, with almost anything, the C63 wasn't quite perfect. This power and performance had a downside. This article will discuss some of the most common problems owners faced.

By Tom Cavanagh - May 4, 2015

This article applies to the Mercedes-Benz C63 AMG w204 (2007-2014).

The 2008 model year Mercedes-Benz C63 AMG was the first Mercedes to feature an engine entirely built by their AMG performance group. It was introduced to compete with the BMW M3. Its 6.2 liter engine produced 518 horsepower and 465 foot-pounds of torque. Most of the C63's problems arose from trying to "tame the beast's" M156 engine. Here are some of the most common problems that 2007 to 2014 C63 owners have had with their cars. As you will note, many of these problems can be related to one another.

Problem 1 – M156 head bolt failure

Shortly after its launch in late 2007, C63 owners started noticing clicking noises as soon as the engine was started. Oil levels rose, while engine coolant constantly needed "topping off." Then, a large number of the M156 engines started failing. There were head gasket problems, bent rods, and ruined engines. Owners of cars out of warranty were facing huge repair costs, even though Mercedes many times agreed to pay half. Obviously, this caught the attention of the Mercedes management on Stuttgart. The cause of these problems was discovered. The head bolts installed on the M156 engine were corroding and failing.

Figure 1. Corroded head bolts.

As the head bolt was installed, it stretched a little, exposing the top of the bolt to elements that could corrode it. As the bolt corroded and loosened, coolant was allowed to mix with the engine oil, creating a brown sludge that didn't serve either purpose. When the bolt top snapped off, a major head gasket problem could follow.

Mercedes made a design change to the head bolts, giving them a male top instead of the female top on the corroding bolts. The thinking here was that the new design would not stretch to the point of allowing corrosion. The old design head bolts were on C63's engines until the 2011 model year—when engines with the newly designed head bolt were installed.

Figure 2. Old vs. new head bolts.

The new head bolts were installed starting with M156 engine #60658. If you know where to locate it, you can check your engine number. Some owners' forums report finding numbers less than 60658 on 2011 C63s. Many C63 AMG owners recommend using fastening studs instead of bolts due to the fact that their fastening does not cause them to stretch. Figure 3 shows some M156 head studs from Weistec.

Figure 3. Weistec replacement head studs.

Problem 2 – Camshafts and lifters

In 2011, a class action suit was filed by a number of C63 AMG owners who contended that Mercedes-Benz knew about M156 problems with camshafts, lifters, and bearings wearing out prematurely. That led to thousands of dollars in repair costs for customers. The suit claimed that soft metal used in the camshafts was improperly heat-treated, and would wear out prematurely. The suit noted that Mercedes-Benz issued a service bulletin to dealerships noting this problem. No corrective recall was ordered. In January 2011, the suit filed by the U.S. District Court was dismissed.

Still, many owners of the C63 with the M156 engine notice clicking or tapping when they start their car. Most of the time, it will subside after about 5 to 10 minutes. This engine is known to experience oil "bleed down." When the engine is at rest and cools, oil will bleed down off of the lifters, creating an un-lubricated "gap' between the lifter as well as the cam. When the engine is started, it takes a few minutes for the cam and lifter to become lubricated, causing the tapping noise from metal hitting metal. Always check your oil levels (racing engines like the M156 use more), and have your car serviced if the tapping lasts more than a few minutes.

Figure 4. The camshaft is being rounded off due to improper oiling and lubrication.

Problem 3 – Unpleasant interior odors

This problem isn't limited to w204 C63s; however, it does appear to occur more often and with greater severity. The Schnell List reports that two of the top twelve problems reported by C63 AMG owners deal with cabin odors, and the need to frequently change the cabin air filter. There seem to be two culprits here. One is the natural odor of interior leather and trim materials. Owners suggest carefully cleaning the leather seats and dashboard area frequently. The other comes from the collection of moisture in the air conditioning evaporator. Mold, mildew, and bacteria thrive in this warm, moist environment. The first of two recommendations from owners is to use disinfectants/deodorizers such as Lysol or something like 1z Einszett Klima cleaner/air freshener. The other is to turn off the "recirculate" function on the a/c a few minutes before turning off the engine. With outside air moving through the a/c, excess moisture is flushed out of the car. Owners also suggest regularly changing the cabin air filter.

Figure 5. Replace the cabin filter.

Related Discussions, and Site