2000 — 2005
2.6L V6 (M112) - C240 Elegance/Avantgarde
Petrol
Check for engine misfires under heavy load | Note: The M112 V6 uses a twin-spark system; ignition coils fail and the 12 spark plug wires become extremely brittle over time from engine bay heat, leading to rough acceleration.
Inspect transmission electrical connector plug | Note: Look underneath near the transmission housing for signs of oil contamination at the 13-pin connector. Fluid wicking up the wiring harness can permanently damage the Transmission Control Module (TCM).
Cycle the climate control system and listen to dash | Note: Listen for a repetitive 'ticking' or 'clicking' sound for 30 seconds upon starting; the heater box blend door actuator gears break, requiring an 8-10 hour extensive dashboard removal to repair.
Scan for SRS/Airbag warning lights and test all cabin electronics | Note: Given the complex electrical architecture, check all window switches, seat adjustments, and scan for SRS lights caused by a faulty passenger seat occupancy sensor or steering wheel clock spring, which causes instant NZ WOF failure.
Examine the Crankshaft Harmonic Balancer Pulley | Note: Inspect the front of the engine to check the rubber damping ring on the crank pulley for cracking or wobbling while idling. A separated harmonic balancer will disintegrate, shredding the serpentine belt and destroying the engine timing cover.
Recommended interval to perform a comprehensive automatic transmission fluid, gasket, and filter flush on the 5G-Tronic (722.6) gearbox to protect the gearbox health and prevent conductor plate failure.
Major service milestone. Inspect the original water pump, plastic thermostat housing, and coolant expansion tank for signs of weepage, and perform the comprehensive 12-spark plug service along with checking for brittle wires.
Review all rubber chassis components including front lower trust arms, control arms, steering ball joints, sway bar links, and rear subframe mounts which soften significantly on New Zealand roads.
Critical check and replacement point for the hydraulic engine mounts and transmission mount, as they settle completely by this mileage, causing severe drivetrain vibration to transfer into the cabin.
Verify that the cooling system has been serviced with genuine Mercedes-approved MB 325.0/326.0 (Blue) coolant to prevent internal corrosion.
Ensure the cabin air filter is fresh, as a clogged one restricts airflow and puts unnecessary electrical strain on the blower motor regulator.
Check that the spark plug service has been performed; remember this engine features a twin-spark system using 12 spark plugs and fragile high-voltage wires, making replacement labor-intensive.
Confirm the brake fluid has been flushed every 2 years to prevent moisture accumulation and ABS/ESP hydraulic pump assembly corrosion.
Inspect the harmonic balancer pulley for rubber separation and check the belt tensioner/idler pulleys for play or squeaking during a cold start.
Clean the Mass Air Flow (MAF) sensor periodically to maintain accurate fuel trims, crisp throttle response, and prevent rough idling or misfires under load.
Estimated repair costs if issues arise
If experiencing erratic shifting, gear hunting, or limp mode (stuck in 3rd gear), the internal electronic conductor plate and speed sensors need replacement. Includes transmission oil service.
To restore the classic Mercedes ride quality and pass New Zealand WOF, expect to replace the front lower trust arms, control arms, and ball joints as a set.
M112 V6 engines frequently leak from both the main gaskets and the upper breather chambers, dripping oil onto hot exhaust manifolds and causing smoke/burning smells inside the cabin. Requires meticulous cleaning and resealing.
If the dashboard clicks upon startup, the plastic HVAC gears are stripped. The parts are cheap, but the massive dashboard disassembly labor dominates the cost at local Euro workshops.
Required every 100,000km. Due to the double spark plug setup per cylinder and extremely cramped access at the rear of the engine block, local specialist labor is high.
Critical breakdown prevention; replace the radiator, water pump, and plastic thermostat housing if they are original or showing signs of weepage.
Noticed something inaccurate or missing?Suggest an edit→
Disclaimer: This report is generated with the assistance of AI analysis based on verified automotive data. While we strive for 100% accuracy, enthusiasts should always conduct physical inspections and consult service records. View Full Disclaimer