Um....I always thought that if you had a serpentine belt then that was the ONLY belt you had on your engine.

I wish. The 545i has 2 belts off the crank pully - a 'standard' belt to run the AC compressor, and a serpentine that runs everything else. Fun lol.

Now Now boys -great advice from both of you.
I do have a similar problem. If I stop and turn the engine off for say 5 minutes and restart then I get temperature warnings etc. I stop the car, switch off and restart all well? I have asked my tech and he says that there are no error codes. When restarting the fan does not even come on immediately
My car has 123,000 miles on. I have not replaced the hoses as yet except the one above the radiator.
My only clame to fame is building 50 different engines and too Porsche 911 3.0lit

advancedlogic,

Did you solve this problem?

I am seeing the same behaviour and have replaced thermostat, water pump and temp sensor on the pump housing without any change to the overheating warnings. The car runs fine and temperature readings on the OBD are perfectly stable. I am at a loss.

Thanks,
Mikael

I haven't had this since the last post.

Hey guys the problem remains. Sometimes it'll go in rapid succession, then quiet. Some days are quiet. I think it's a problem within the DME, or possible voltage destabilization. I am a few months in on a rebuilt alternator, but I am going to bite the bullet on a brand new unit. Thermostat, water pump, thermal sensors, overflow tank, hoses, etc have all been replaced at one time or another. I'm going to resistance-check my battery cable and connections once time permits. I've had an MPM and IBS replacement in the past as well. Years of this warning, and 50k+ miles additional miles since the first time it popped up, I am fairly confident its a BS warning in my case lol. Still, the worst part is the system will turn off the AC when the warning pops up, ostensibly to reduce engine loads (and reduce temps in real emergencies). In my case, it just annoys the hell outta me with warming air for a moment.