Mercedes-Benz G63 AMG W463 Reliability

2012 model M157 engines have a critical oil drainage issue from the cylinder head on cold start-up. This leads to brief oil starvation of the timing chain tensioner, causing the chain to stretch. Mercedes installed a check valve and revised tensioner/guides on 2013+ engines, so 2012 models are most affected. Listen for rattling on cold start - if present for more than 2-3 seconds, the chain, guides, tensioner, and sprockets all need replacing. Ignoring this leads to timing chain skip and catastrophic valve/piston contact. Replacement requires significant labor as the front of the engine must be disassembled.

The conductor plate inside the 722.9 transmission breaks down internally, preventing the control module from monitoring input shaft speed correctly. This causes ineffective torque converter lock-up and harsh gear changes, especially when cold. Common fault codes are P0717 (no turbine speed signal) and P0718 (turbine speed sensor intermittent). The transmission holds too long in one gear before aggressively forcing the next, causing jerky shifts. There are three VGS versions - VGS1 requires both valve body and conductor plate replacement, while VGS2/3 allow conductor plate-only replacement. Repair services can eliminate the need for programming, but only if you know which VGS version you have.

One owner of a 2015 G63 with 45,000 km and full dealer service history had both front turbos fail simultaneously, requiring replacement along with motor/transmission mounts and cam cover resealing - total cost around €23,000. The M157 shares turbo failure issues with the M278 base engine. Labor is extreme because the engine must be dropped to access the turbos. Symptoms include check engine light, loss of power, and unusual whistling sounds. Skipping oil changes or using incorrect oil accelerates turbo wear through internal scoring. The M157 doesn't like short trips - it needs to warm up fully and be driven hard occasionally to prevent carbon buildup that can damage turbos.

The M157's Alusil block is susceptible to cylinder scoring, particularly on cylinders 1, 4, 5, and 8. Cold starts push excessive fuel through the cylinders, washing oil off walls and allowing rings to score them. There's also an oil pump solenoid that reduces pressure during low-load running for efficiency - if it fails in low-pressure mode, it's catastrophic. This is less common in Europe where top-tier fuel is standard. Prevention: short oil change intervals (5,000 km max), MB 229.5 approved synthetic oil, premium fuel only, and proper warm-up before hard driving. The Alusil block can be sleeved and rebuilt with forged internals for less than a new engine, but sleeves compromise piston cooling. Some question why Mercedes used Alusil in the M157 when the M156 had superior TWAS coating.

Camshaft adjusters fail on M157 engines, typically before 100,000 km and often as early as 50,000 km. Symptoms include cold start rattle lasting several seconds, long cranking (2-3 seconds), check engine light, rough idle, misfires, and ticking/clattering noises. When the adjuster fails, the pulse wheel misaligns causing erratic engine behavior. Replacement requires engine removal and disassembly. Dealer quotes run €6,000 for both driver-side adjusters, while independent shops charge around €2,000-4,300 depending on which bank. Using high-quality oil meeting Mercedes specifications and following service intervals helps prevent premature failure. A set of 4 valve timing phasers can be remanufactured for less than buying new.

Air suspension struts leak as rubber becomes brittle and cracks with age and temperature fluctuations. You'll notice the vehicle sagging on one side or lowering unevenly, especially after sitting overnight. Warning messages include "Air Suspension Failure, Visit Workshop" and in severe cases "STOP VEHICLE TOO LOW" in red. Compressor failure prevents the system from adjusting ride height, resulting in rough ride and reduced ground clearance. Level sensor failures at front/rear suspension prevent the system from recognizing vehicle height. Replacing one air spring costs over €2,500 according to RepairPal. Some owners convert to coil springs to eliminate ongoing air suspension problems - a one-time cost that removes future air leaks and compressor issues.

The M157 uses an electric water pump integrated with the thermostat housing. Failures are common at high mileage, typically around 80,000-100,000 km. Symptoms include coolant warning light, engine overheating, or poor cabin heating. When replacing the pump on M157/M278 engines, also replace the turbo coolant lines - Mercedes used plastic fittings that fail during the repair process. The thermostat has plastic clips on the water pump side that snap during removal, making it unusable. It's a 10-hour job at dealers costing around €2,300 in labor alone, plus parts. Some owners perform preventative replacement around 80,000 km. Independent specialists can save around €1,000-1,500 compared to dealer pricing.

Oil leaks from valve cover gaskets and timing cover seals are common on higher-mileage M157 engines. Oil seeps from the top of the engine (valve covers) or front (timing cover). The M157 is "somewhat notorious for timing cover seals eventually leaking oil." Dealer quotes for valve cover gasket replacement run €2,000-2,680, though independent shops can do it for less. Individual gaskets cost around €20-30 from aftermarket suppliers, but labor is expensive due to the complexity of accessing them in the biturbo V8 engine bay. Other common leak points include the oil pan gasket and oil filter housing gasket. Regular inspection and timely resealing prevents major damage from low oil levels.

W463 rear window regulators are a well-known failure point. The plastic device connecting the cable to the tray breaks, especially when someone presses the button after the window has reached its lowest position. Daily use wears down cables, gears, and plastic guides. Rain, humidity, and temperature extremes (freezing winters, hot summers) make plastic parts brittle and cause corrosion. Some believe non-use contributes to failure. Symptoms include slow window operation, crooked glass as it rises, sharp clicks or gritty grinding inside the door, and windows slipping down without warning. Dealer quotes run around €496, while aftermarket sources quote €289. There are two design types - original (pre-2009) and improved (2009+). Replacement is fairly straightforward - clamp the glass in the up position during replacement to prevent it falling and breaking.

Some owners believe this is a design flaw in the G-Class where water flows through the sunroof into the tray, then leaks into the truck causing wiring harness corrosion. Owners report soaked headliners after rain/wind storms even with all windows and doors closed. The drainage tubes behind the pillars running down the car become clogged with leaves and dust. Small hoses have grommets that can become completely blocked. If left unchecked, water damage can corrode the O2 sensor wires on catalytic converters, damage electrical systems, cause mold, and impact resale value. Fix: Open sunroof, access the small drain openings, and use thin wire to clean them - you'll see water beneath the car when successful. Preventative maintenance includes cleaning the sunroof at least once yearly (especially in fall), applying special grease to rubber seals, and greasing the rail mechanism.

HVAC outlet vents in the dashboard cracking is a well-documented W463 issue. The core W463 parts are robust, but update parts like dashboard vents are not. The arm-to-motor linkage has a cheap plastic arm that cracks. The "new" design has a beefier build but still fails. Vent flap motors that control airflow direction get stuck, causing hot or cold air on one side only or inability to switch between vents. The blower motor responsible for circulating air is prone to failure - owners report intermittent fan operation, strange noises from vents, or complete blower failure. Replacement requires dashboard disassembly making blower motor repairs costly. Genuine Mercedes replacement vents range from €51 to €184. Other related interior issues include main window switch failures and headliner sagging.

Modern Mercedes modules (infotainment, security alarms, GPS) operate in standby mode. If a control module like the signal acquisition module fails to enter sleep mode, excess power draw depletes the battery. Other causes include faulty wiring, stuck relays with corroded contacts, interior lights, faulty switches, power seats, or passenger seat adjustment/memory modules. Normal draw is under 50 milliamps - anything higher indicates parasitic drain. Diagnosis: Let car sit 15-30 minutes with key removed, then measure current draw with multimeter. Pull fuses one at a time to identify which circuit drops amperage. Solutions: Reset battery management system (disconnect negative terminal 10-15 minutes), enable Battery Saver mode in settings, get TSB software updates, disable proximity key function in high-traffic areas. If equipped with Intelligent Battery Sensor, perform battery reset after replacement using diagnostic tool.