2004 bmw x3 3.0 on 2004 BMW X3

overheating problem.expanson tank bleuw up.so i replaced the expansion tank,thermostat and the rad.fan switch still over heating in the trafic.how do i check the rad fan if it is working or not

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3 answers
test the fan 1st with power and ground
Start it up, ac off, and let it run at ilde. The fan should come on, after awhile, before it overheats!
On your vehicle you have a primary fan (Mechanically operated by fluid displacement) Only way to test the fan clutch is with engine off and cold engine. Carefully inspect if front of fan clutch is oily? Indicating not enough internal fluid to operate as designed. Also have your secondary fan (electrically control) because sounds like that was the cause of original cooling system failure.