Mercedes-Benz GLS Operator's Manual page 627

Engine
Warning/indicator lamp
Possible causes/consequences and
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The red coolant warning lamp is lit while the engine is running.
*Possible causes:
R
Coolant warning lamp
R
R
R
If there is an additional warning tone, the coolant temperature has exceeded the maximum permissible temperature.
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If the coolant temperature display is at the lower end of the temperature scale:
The temperature sensor is malfunctioning
Coolant level too low
The air supply to the radiator is obstructed
The radiator fan is faulty
& WARNING Danger of burns when opening the hood
If you open the hood when the engine has overheated or during a fire in the engine compartment, you could
come into contact with hot gases or other escaping operating fluids.
Before opening the hood, allow the engine to cool down.
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In the event of a fire in the engine compartment, keep the hood closed and call the fire service.
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Stop the vehicle immediately in accordance with the traffic conditions and switch off the engine. Do not continue
driving under any circumstances.
Note the messages on the multifunction display.
Display messages and warning/indicator lamps 625
M M Solutions