What can it be? Please help, urgent now.
Howzit Guys,
Well now my cooling problem is a more seriouse issue. 
Here's the problem:
When I start her up, she takes the normal 5 - 10 minutes to get to operating temp. Also she takes around 5 minutes when driving to get warm. Now while I'm driving at around 60 or higher, my temp remind half way. Any slower or even if I idle the car for 1 minute, she will get hot and if I don't start moving or if I don't turn it off, she will overheat. 
Here's what I've checked:
Thermostat:
I let the engine warm up, once it got to normal temp, I felt the hose going to the radiator and it was hot to the touch, no cool spots at all. This is telling me that the T-Stat is indeed working fine?
Coolant Level:
I have made sure it is at the COOL mark, however I still get the *Bing* "Coolant Level" on my dash for some reason?
Clutch Fan:
Okay, I'm not a 100% sure this fan is working 100%, if I start the engine, fan come on straight away. When I shut the engine off, the fan turns off one or two seconds later, well, stops spinning. But I'm not sure it's blowing enough air though to the radiator? Anyway to test this?
I'm really at a loss with the problem. No idea what's causing this. See if I drive the car it's perfect. If I stop and idle for less then a minute, temp gauge goes past half way. 
Anyone know how I can find out what the problem is here?
Any help would be greatly appericated.
Thanks a lot guys!
Car: BMW 525iA.
Engine: M20.
Trans: Auto.
Year: 1990.
Location: Durban, South Africa.