Mercedes-AMG C63 W205

This is the most significant M177-specific issue. The oil separator in the crankcase ventilation system can become clogged with blow-by residue over time, especially on cars driven hard. When the separator fails, crankcase pressure increases and forces oil past the rear main seal where the engine meets the transmission. Symptoms include oil dripping from the rear of the engine, a burning oil smell, and visible oil around the bellhousing area. Crucially, replacing only the rear main seal without fixing the oil separator will result in the leak returning. The repair requires transmission removal for access to the rear main seal. At a specialist, expect €2,000-3,000 for the combined oil separator and rear main seal replacement. At a Mercedes dealer, costs can reach €3,500-4,500. If oil has contaminated the Integrated Starter Alternator (ISA), that component must also be replaced, adding significantly to the total. Typically appears after 60,000-100,000 km. Regular oil changes with quality 0W-40 help slow the progression.

The M177 produces substantial torque that stresses the factory hydraulic engine mounts. The left (passenger-side) mount is especially prone to failure and has gone through multiple part revisions, indicating a design weakness. When the rubber housing cracks, the internal hydraulic fluid leaks out and the mount loses its damping ability. Symptoms include excessive engine vibration at idle, clunking when shifting into drive or reverse, and vibrations felt through the steering wheel. OEM mounts cost approximately €400-500 each, with total parts and labour running €800-1,200 at a specialist or up to €1,800 at a dealer. The issue can appear as early as 30,000-50,000 km on cars driven aggressively, though most failures occur between 60,000 and 100,000 km. Aftermarket upgraded mounts with stiffer polyurethane elements are available for around €300 per side but increase NVH.

Ignition coil failures are among the most common M177 complaints. Mercedes has issued three different part numbers for the M177 ignition coils (A1779069500, A1779064202, and A1779060206), indicating ongoing reliability concerns with successive revisions. Symptoms include rough running, misfires under load, loss of power, and check engine light. Typically occurs between 60,000 and 100,000 km. Individual coil replacement costs approximately €50-80 per coil plus labour, but since the V8 has eight coils and failures tend to cascade, replacing all eight preventively is recommended. A full set with spark plugs runs approximately €400-600 at a specialist or €700-1,000 at a dealer. The issue affects both standard and S variants equally.

Like all direct-injection engines, the M177 suffers from carbon buildup on the intake valve stems and ports because fuel is injected directly into the cylinder rather than washing over the valves. Over time, carbon deposits restrict airflow, causing reduced power, rough idle, and occasional misfires. The M177 does not have port injection to mitigate this. Walnut blasting (media blasting of the intake valves with the manifold removed) is the standard cleaning method. Typically needed between 80,000 and 120,000 km depending on driving style. Short trips and gentle driving accelerate buildup. Cost at a specialist is approximately €800-1,000, or €1,200-1,500 at a Mercedes dealer. Italian tune-ups (regular spirited driving at higher rpm) can slow the accumulation.

The turbo wastegate flappers develop play over time and vibrate against their seats during partial-load operation, producing a metallic rattling sound. Mercedes issued Technical Service Bulletin LI09.40-P-061542 acknowledging the noise, stating that the turbochargers are technically fine and should not be replaced for noise alone. However, the TSB also notes that the software fix available for non-AMG models (adjusting wastegate actuation timing) cannot be applied to AMG engines due to different pressure and actuation conditions. Aftermarket stainless steel wastegate repair kits are available for €200-400 in parts, with labour around €300-500. If the turbo internals are eventually damaged from prolonged flapper wear, a full turbocharger replacement costs €2,000-2,500 per side. The rattle is cosmetic initially but can worsen to the point where boost control is affected.

The C63 S uses a Drexler electronic locking differential, while the standard C63 uses a mechanical limited-slip unit. The e-diff is more sophisticated but also more expensive when it fails. Reports of failures around 20,000-40,000 km exist, though these are disproportionately from tuned cars or those used for drag racing with repeated hard launches. Mercedes has stated that if differential oil changes are not performed as scheduled, warranty claims may be refused. A replacement e-diff unit costs approximately €4,000-5,000 for the part, with labour bringing the total to €5,000-8,000. The standard C63's mechanical diff is significantly less expensive to service and more robust, making it the lower-risk option from a reliability standpoint. Listen for whining under throttle and groaning when turning at low speeds.

Interior rattles are one of the most frequently reported W205 C63 complaints, and they affect nearly all examples to some degree. Common sources include the driver door and window area, dashboard (particularly the gauge cluster surround), speakers, centre console, and door trim panels. The noise is often temperature-dependent and worse in cold weather as plastic contracts. Mercedes has acknowledged the issue, but dealers have difficulty permanently fixing it because the rattles migrate between panels. Many owners resort to DIY fixes using felt tape on trim contact points and securing loose clips. Professional rattle-proofing by a specialist costs €200-500, while dealer attempts are typically covered under warranty but rarely resolve the issue permanently. The problem is cosmetic and does not affect the car's mechanical function.