BMW coolant temperature warning
A red coolant temperature warning (a thermometer in liquid, or an "engine hot" message) means the engine is overheating. Stop where it's safe and switch the engine off: driving on can warp the cylinder head or damage the head gasket.
A yellow coolant level warning means the coolant is low. Let the engine cool before opening the expansion tank: the system is under pressure when hot.
Usual causes
- Low coolant from a leak: the expansion tank, the radiator, hoses and their plastic fittings, or the water pump.
- The water pump: on many BMW six-cylinder engines from about 2006 on it's electric, and its failure is a known cause; it reports its faults to the engine module.
- The thermostat, stuck closed.
- The electric cooling fan or its control.
- A coolant level or temperature sensor giving a wrong reading.
What to do
- Stop and let the engine cool. Check the coolant level in the expansion tank once it's cold, and look for leaks under the car and around the engine.
- Read the engine module's faults: the electric water pump, the thermostat and the fan report faults there, with the temperature when they happened.
- Top up with BMW-approved coolant, fix the leak, and bleed the cooling system as the car's procedure says: trapped air causes overheating too.
General guidance from how BMWs work, not a diagnosis of your car: the fault the module stored, with its details, tells you more.
The fault codes behind it
- Engine electronics fault codes 5694 codes · E46, E52, E53, E60, E61, E63, …
Reading the fault
AutoLingo for BMW reads the fault behind the light from the module that stored it, in plain English and with its details, and clears it after the repair, with BMW's own diagnostic protocols: a generic OBD2 code reader only reaches the engine's emissions faults. See what it does on your BMW.
Questions
- Can I drive with the coolant warning on?
- Not with the red warning: stop and switch the engine off, or it can be damaged badly. With the yellow coolant level warning, top up once the engine is cold, then find the leak.
- Why does my BMW overheat with a full coolant tank?
- Usually something isn't moving the coolant or the heat: a failing water pump, a thermostat stuck closed, the cooling fan, or air trapped in the system after a repair.
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