When the engine is running, the red indicator light flashes
There is too little coolant in the circulation system
The expansion tank must be filled to the maximum mark. If necessary, add liquid. Check the cooling system for leaks.
Thermostat does not open. Coolant circulates only in the small circuit
Check if the outlet (upper) radiator hose gets hot. If not, remove and check the thermostat. Replace it if necessary.
The water pump is faulty
Remove and inspect the pump.
Coolant temperature gauge is faulty
Check the sensor and indicator on the instrument panel.
Defective expansion tank cap
Check the cooling system under pressure.
The radiator fins are dirty
Blow out the radiator from the engine side with compressed air.
Radiator is clogged with limescale or rust. Radiator warms up only at the top, lower radiator hose remains cold
[Text republished from the website: MERCEDESMAN]
Replace the radiator.