Diagnostic: Engine overheating on Mercedes-Benz - Causes and costs

Engine overheating on a Mercedes-Benz (A, C, E Class, GLC) shows as the temperature warning light coming on or the needle going into the red. Depending on petrol (M264, M260) or diesel (OM654) engines, common causes and costs differ.

Mercedes: common causes

On M264, M260 and OM654, overheating is often linked to the thermostat stuck closed (coolant no longer flows to the radiator), radiator clogged or blocked, water pump failure (timing or auxiliary belt), low coolant level (leak: hoses, head gasket, expansion tank) or fan (electric or viscous) not engaging.

What to do

As soon as the temperature light comes on: reduce load (slow down, avoid hills), turn heater on full. If temperature does not drop: stop, engine off, do not open the radiator cap when hot. Wait for cooling before checking level. Have the system checked by a professional.

Order of magnitude for costs

• Thermostat: about €130–350.
• Water pump: about €220–550 (timing belt if driven by it).
• Radiator: about €280–650 (part and labour).
• Head gasket: about €1,100–2,800 and more depending on engine.
• Fill and bleed: about €90–180.

My Auto Check-up helps you prepare your visit by gathering information for an initial cost estimate.