engine problem again overheating this time !!!!

[jondee86]

There are complicated thermodynamic explanations/theories that can
explain what happened. At high speed the effect of the fan is negligible.
All the airflow for cooling comes from the airflow generated by the
forward motion of the car. I have removed my viscous fan for circuit
racing (every little bit helps ) without any sign of overheating.

What can happen is that the cooling system is operating very close to
maximum heat transfer capacity, with high airflow thru the radiator.
When you stop the vehicle/reduce the engine speed to an idle, a type
of "heat-soak" occurs. There is heat stored in the metal of the engine
that continues to enter the cooling fluid for a few minutes after the car
stops. If the heat gain to the fluid is greater than the heat loss thru
the radiator, the engine can boil.

This is the purpose of the cool-down lap for racing cars... to allow the
stored heat in brakes and cooling system to be passed out to the air
without overheating.

Cheers... jondee86