Thermostat M278 for Mercedes-Benz

OE-spec engine thermostat assembly for Mercedes-Benz vehicles with the M278 4.7L V8 biturbo engine. Restores correct warm-up time and stable operating temperature, and protects against overheating and weak heater performance.

Key Features

• Precise Temperature Control: OE-matched opening temp and flow for stable engine and cabin heat.
• Integrated Housing and Seal: Direct bolt-on replacement to minimise leaks and comeback repairs.
• Correct Sensor/Actuator Logic: Works with the ECU for accurate warm-up and efficiency.
• Exact Fitment: Factory mounting points for a no-mod install.

Compatibility

Common applications with the M278 V8 biturbo: S-Class W221 late/W222 early (S500/S550), E-Class W212 (E500/E550), CLS C218/X218 (CLS500/CLS550), GL W166/GLS X166 (GL500/GLS500/GLS550), ML W166/GLE W166 (ML500/ML550/GLE500 where fitted), and select G-Class W463 trims (G500/G550 in some markets). 2WD and 4MATIC where applicable — always match by VIN.

Note: Coolant, hoses, clamps, water pump, radiator, and extra sensors/hardware not included.

This is an aftermarket replacement part, not a genuine Mercedes-Benz product. Not affiliated with or endorsed by Mercedes-Benz Group AG.