Mercedes-Benz C 300 e
Four-cylinder turbo with 48V belt starter-generator. Modern, efficient engine with EQ Boost mild hybrid. Timing chain long-lived.
320 hp System Output
235 kW system output from turbocharged four-cylinder and electric motor — immediate response and boost sensation.
Engine Weaknesses 12
Defective exhaust valves and soft valve guides lead to severe cylinder head damage. Often just after the warranty expires. Mercedes USA extended the warranty to 15 years/150,000 miles.
Symptoms: Sudden severe misfires, CEL flashing, power drop, dangerous stalling at motorway speed
The electric motor is integrated into the 9G-Tronic. With faults in the high-voltage cables the gearbox must be removed — extremely costly repair.
Symptoms: Fault message 'Hybrid drivetrain disturbed', no electric drive possible, vehicle runs as pure combustion engine only, sometimes emergency shutdown
The hydraulic chain tensioner on the M264 can lose oil pressure after extended standstill. On cold start the timing chain rattles briefly until oil pressure builds.
Symptoms: Brief rattling on cold start (2–5 seconds), disappears after warm-up
The integrated starter-generator (ISG) of the M264 EQ Boost system can fail. Start-stop function and boost support are lost. Expensive replacement.
Symptoms: Start-stop function deactivated, no EQ Boost on pull-away, 48V system fault message, rougher engine start
The M264 uses multiple electric coolant pumps. Internal motor defects trigger fault codes. Bleeding requires the Mercedes diagnostic tool.
Symptoms: Coolant temperature warning, fault codes P0A0500/P00B700/P0C7300, irregular engine temperature
The PHEV lithium-ion battery measurably loses capacity at high mileage. Faulty temperature sensors can trigger emergency shutdown of the hybrid drivetrain.
Symptoms: Electric range drops significantly, warning 'Stop immediately', unexpected shutdown of hybrid drivetrain
The 48V lithium-ion battery of the EQ Boost system loses capacity over time. With severe degradation the boost function is curtailed.
Symptoms: Reduced EQ Boost output, more frequent start-stop deactivation, 48V warning on display
The camshaft adjuster solenoid valves on the M264 can leak internally. Variable timing no longer functions correctly, engine runs rough.
Symptoms: Rough idle, camshaft position fault codes, slight power loss in the lower rev range
Direct injection without port injection leads to carbon deposits on intake valves, especially with short-trip use. Impairs intake flow and combustion.
Symptoms: Hesitation and rough idle from approx. 80,000 km, slight power drop, elevated fuel consumption, knock tendency under load
The OPF requires temperatures above 600°C for active regeneration. With frequent short trips under 10 km the filter cannot regenerate and becomes progressively blocked.
Symptoms: Check engine light, elevated fuel consumption, forced long-distance drive needed for regeneration, engine power reduced
Turbocharging and direct injection thermally stress spark plugs more heavily. Ignition coils can electrically fatigue at high mileage and cause misfires.
Symptoms: Misfires, rough engine running, hesitation on acceleration, check engine light, poor throttle response
Valve cover gasket and rear crankshaft seal tend to leak at higher mileage. Oil loss on the hot engine can cause smoke.
Symptoms: Oil smell when parked, visible oil puddles under the vehicle, dropping oil level, bluish smoke from engine bay
Vehicle Weaknesses 7
Longitudinal members, jack-point attachment holes and rear axle subframe rust through. MB offers goodwill replacement.
Polycarbonate blind cover of the panoramic roof incorrectly bonded. When opening, the blind can come loose. Recalled by MB.
Ball joints on the wheel-side wishbone and rubber-metal bushes wear. New suspension geometry makes repairs more involved.
Some W205 models discharge the battery unusually quickly during extended parking. Cause: elevated quiescent current draw from control units.
The W205 shows above-average front axle issues from the second MOT onwards according to TÜV statistics. Worn control arms and drop links are the main causes.
W205 A/C fails with 'Air conditioning off' without a fault code in the onboard computer. Often the compressor or A/C control unit is defective.
Panoramic roof on the W205 creaks when opening and closing. Guide linkage can bend and jam the roof. Repair often requires complete removal.