Mercedes: 86 Mercedes 300E overheating after 5 minutes, blown head gasket, fan clutch

Question
My 86 300E has been running very hot lately (Tucson, AZ). Recently it ran into the red. Now when I start the car it runs for 2-5 minutes and goes straight into red zone. No leaking from the water pump, both fans are running, no indication of a blown head gasket. From what I have read, the next place to look is the fan clutch. Will this affect the car so quickly (2-5 min.)? Please help, I am carless until this gets fixed.

Answer
Answer:
First rule of overheating; replace the thermostat...
Second rule of overheating; replace the thermostat...
Third rule of overheating; refer to rule one and two before going any further...

After replacing thermostat, you may consider the following:
#1. Plugged radiator.
#2. Bad water pump.
#3. Plugged catalytic converter may be possible.

Bad fan clutch should take seven to fifteen minutes from cold start to overheat.