My 1989 520i Bmw is overheating still. The thermostat, radiator, fans, water pump and fan clutch are all working fine. When I start the car, the temperatuture needle moves past the 12:00 mark and heads for the red.I first noticed the overheating when I was driving in traffic. I stopped the car as soon as I noticed that the guage was close to the red zone. Help!!!!!!!