E39 electric fan sound very loud

[sewell]

Hi, i am new to the forum and new owner of E39 520 year 2003.each time i start my engine (the temp is in working working temp) my electric fan spin to the higher speed for 10-20sec then the fan will slowly adjust accordingly to lower speed. my machanic asked me to change the thermostat and the problem still the same. is it the radiator block or something has to do to the aircond? sifu please help.

 

[funfer_fahrer]

The radiator outlet sensor could be at fault. It could be sensing high temp most of the time. Sometimes, it may take a couple of days before can register in the ECU.

 

[bimmer73]

Sometime when you start your car the fan turns at High speed when your engine is a little hot.

 

[bimmer73]

And also check the thermostat sometimes even brand new it does not work and there are two types of thermostats. Hi temp and low temp...

 

[transporter]

bimmer73, how to know whether it is high or low temp ? just replaced mine for 190 bucks not sure which it is...thanks..

 

[jarance]

Thermostat switch is for cutting in the fan. Shouldn't there be a temperature sensor to control the speed of the electric fan?

 

[jarance]

Extract from BMW WDS for E39.

Electric Fan
Vehicles with M62TU, S62 and M73 engines feature a viscous fan as well as an electric fan. The electric fan cuts in when the cooling capacity of the viscous fan is no longer sufficient.

The electric fan is activated by means of a power output stage directly on the fan motor. The motor control unit activates this power output stage by means of a square-wave signal with duty factors (variable pulse width) between 10 % and 90 % thus controlling the various speeds of the electric fan. Pulse duty factors less than 5 % and greater than 95 % do not trigger activation but rather they are used for fault detection purposes. The power output stage features its own positive and ground supply.

The fan speed is influenced by the coolant temperature at the radiator outlet and the pressure in the air conditioning system. The fan speed is reduced as the vehicle speed increases.

If a fault occurs during operation a corresponding fault code will be stored in the fault code memory of the DME control unit.

For the purpose of checking operation and troubleshooting, the diagnostic program offers the option of activating the electric fan directly via the DIS tester/MoDiC.

 

[hvb3025]

check the spare tank of the rediator,, it may have tiny hole or leaks which eyes might not notice.... change the tank