Cooling System
COOLING SYSTEM
The configuration of the M62 cooling system is similar to the former V-8. An aluminum, cross flow radiator is used that contains no soldered, greased or painted surfaces. This makes the unit completely recyclable.
The coolant flows from front to back through the block, rises up to the cylinder heads and exits into the coolant distribution pipe at the rear of the heads. It returns to the radiator through the return pipes located in the "V" of the block.
The M62 engine uses a new design "DME map controlled, heated thermostat". The design concept of the thermostat is to allow the engine to run hotter in the part load operating range (fuel consumption is reduced by approximately 1% for every 10°C increase in temperature).
The heated thermostat is unitized with the aluminum cover. The new thermostat incorporates a heating element that is integrated with the conventional expanding wax core within the thermostat.
A dual coolant temperature sensor is used on the M62 engine and it is now located in the coolant distribution housing assembly. The dual sensor provides individual temperature signals for the temperature gauge and the DME control module. The new location ensures accurate temperature sensing feedback for heated the heated thermostat operation.
The heated thermostat is both a conventionally functioning and DME control led thermostat (two stage operation).
DME control causes the thermostat to open sooner than the mechanical thermostat rating. This provides sufficient cooling for full load and high output conditions.
CONVENTIONAL FUNCTION: The thermostat begins to open at 103°C. This is at the inlet side of the water pump and represents the temperature of the coolant entering the engine.
Before the 103°C temperature is realized, the coolant is circulated through the engine block by the water pump.
After the temperature reaches 103°C it is maintained as the inlet temperature by the thermostat. The coolant temperature at the water pump engine outlet is approximately 110°C. The additional 7°C is achieved after the coolant has circulated through the block.
The operating temperature of the engine will remain within this range as long as the engine is at part load conditions.
DME CONTROLLED FUNCTION
The map controlled heater in the thermostat will switch ON under the following conditions:
^ Load signal "ti" > 5.8 ms
^ Engine temperature "tm" > 113°C
^ Intake air temp > 52°C
^ Vehicle speed > 110 MPH
When the heating element is switched ON, the thermostat is heated higher than the temperature of the coolant.
The thermostat opens sooner causing additional coolant to circulate through the radiator which brings the temperature down.
The temperature of the coolant at the inlet side of the water pump will drop to approximately 85°C and the temperature at the outlet side of the water pump will drop to approximately 103°C.
NOTES:
^ If the coolant temperature is below 85°C, the heater will not switch on for any condition.
^ The display characteristics of the temperature gauge in the instrument cluster have been calibrated to the higher engine temperatures.
^ The M62 engine in the E31 - 840Ci will NOT receive the heated thermostat. The engine will continue to use a conventional 85°C thermostat.