BMW E65 thermostat and engine temperature
E65 engine warms up slowly or temperature won't rise - is the thermostat faulty?
Often it is. If the temperature stays permanently at about 75 degrees or varies a lot, that is not normal. The yellow engine warning light may come on when the engine doesn't warm up fast enough. The cause may be the thermostat.
What is the normal operating temperature of the E65?
The recommended operating temperature for the N62 engine is 85-110 degrees. The mechanical thermostat opens at about 105 degrees, and the controlled thermostat opens the whole circuit between 85 and 110 degrees. The instrument cluster shows the coolant temperature just before the thermostat.
What can cause the E65 overheating warning?
Common causes are low coolant or a poorly bled system, as well as the water pump and thermostat. The car has two thermostats. If no leak is visible, a head gasket failure is unlikely. It is worth replacing the pump and thermostat together and bleeding the system with new fluids.