Which Tstat ?

[jimberg]

You guys are still debating this?

The thermostat DOES open and close during normal operation. If it didn't, we wouldn't need a thermostat. You can actually see the point where it opens if you watch the water temp gauge. The temperature will drop periodically and then rise again.

When the thermostat is closed, it keeps all the coolant where it is. The coolant temperature in the block will start to rise and the coolant temperature in the radiator will start to drop. When the coolant temperature in the block gets hot enough, it will cause the thermostat to open allowing the coolant to flow which will allow the hotter and cooler coolant to mix and reach equillibrium at a temperature that is lower than the thermostat opening temp which causes the thermostat to close. The cycle starts over again.

The hotter the coolant is allowed to get while waiting in the block, the cooler the coolant is allowed to get while waiting in the radiator. Whether it runs too hot or too cool when you switch to a lower temp thermostat depends on the efficiency of the radiator. If you remove your thermostat, your coolant will be too cool if your radiator is better at removing heat than your engine is at addding heat and vice versa.

It would be impossible to match a radiator with an engine so perfectly that the temperature would remain static while the thermostat was open all of the time. The amount of heat your engine generates is not constant and neither is the amount of air flowing through your radiator.