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Discussion Starter · #1 ·
I have a 2001 330ci , I changed water pump and thermostat correctly ,water pump was toasted and the thermostat as well. I put in antifreeze and then I drive my car reading normal temp 12'o clock on temp reading then after a short time of driving it soon climbs up and up (quickly) . I think I bled the coolant system correctly.
 

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See 3rd & 4th link in my signature on engine coolant temperature and how to display on the Hidden OBC on the dash.
 

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// Quandt AG (Retired) //
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I've had overheating issues with my cic for a number of years since the first Aux Fan Relay failed. It's not that the buffered needle would go into the red but I was reading the internal coolant temps and they were way too high for my liking and bordering overheating. Also when I opended the hood of the car after a spirited drive you could feel the waft of heat from the engine. (unlike other e46's after a similar drive)

Turns out the second aux fan relay wasn't processing the PWM signals corectly for the fan speed. I had to replace the aux fan relay (this is the small electronic box that is bolted on the fan - this was near impossible to diagnose since it does not report any codes and also acts as if it is working correctly (spins at startup and turns on when AC is active.). You may have to monitor the fans output when the car is hot to see if it is spinning at a rate sufficient to cool the engine. The fan is a variable speed fan that gets info from the DME including the coolant temp sensor. Check that the sensor is working first as this is a cheaper fix and also check the connections for the fan and relay first to ensure good contact.

I also put in a stewart emp waterpump which is a little more efficient and have had no probs since.
 
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