Fox T-Bird/Cougar Forums  

Locked up fan does not equal full time cooling. Too much air flow through the radiator is nearly as bad as too much coolant flow through the radiator. When the air moves too fast through the radiator, it gets very turbulent, thus, decreasing effective cooling capacity. It's not as bad as the coolant going through too fast, though.

Both of these statements are incorrect.

Fact - Increased air/coolant flow increases heat transfer
Fact - Turbulent air increases heat transfer

Both of these statements are incorrect.

Fact - Increased air/coolant flow increases heat transfer
Fact - Turbulent air increases heat transfer

Coolant Flow Rate

 Looking at the previous expression, we can see that slowing the coolant down is the wrong way to go.  If the heat load is constant, lowering the flow will increase the temperature drop through the radiator, making the bottom tank, or radiator outlet, temperature less than before. If the bottom tank temperature goes down, the top tank temperature must go up to maintain approximately the same average core temperature so that the heat load may be transferred to the cooling air.  At the reduced power setting it would rise above 190 degrees F and at 240 hp the engine would be overheating worse than before.  In fact, because the lower flow rate results in lower coolant velocity and less “scrubbing action” in the tubes, the average coolant temperature must rise slightly in order to transfer the heat load from the coolant to the cooling air, making matters even worse.

What would happen if we increase the coolant flow?  Will it go through the radiator so fast that there won’t be time for cooling to take place?  Not at all, from the expression, we can see that if the heat load is constant, increasing the coolant flow rate will reduce the coolant temperature drop through the radiator, resulting in a higher bottom tank temperature.  If the bottom tank temperature is increased, the top tank temperature must go down to maintain approximately the same average core temperature.  This is what we were hoping to achieve.  With the top tank temperature now less that 190 degrees F at the reduced power point, we can expect  that the system will be better able to run at 240 hp without overheating,  In fact,  because  the increased coolant flow rate results in a higher coolant flow velocity and better “scrubbing action” in the tubes, the average coolant temperature decreases slightly while transferring  the same heat load to the cooling air, further lowering the top tank temperature, resulting in better cooling performance.

From this we see that increasing the coolant flow rate will result in better heat transfer performance.  There are some cautions to be observed in increasing coolant flow rate, however.  Going too far may result in aeration and foaming of the coolant, possible damage to the radiator by overpressure, cavitation of the pump, due to excessive pressure drop through the radiator, and erosion of the radiator tubes.  The ideal coolant flow rate is one that will provide optimum coolant flow velocity through the radiator tubes in the range of 6 to 8 feet per second.  Flow velocities above 10 feet per second should be avoided.

Cooling Airflow

 Cooling air becomes heated as it passes through the radiator.  It enters the radiator at ambient temperature and exits the radiator at some increased temperature.  It is the difference between the average core, or coolant temperature and the average of these two cooling air temperatures that creates the ability of the radiator to transfer heat to the air.  The slower the air passes through the radiator, the higher will be its exit temperature and the higher will be the average cooling air temperature.  The higher the average cooling air temperature, the less heat will be transferred from the coolant to the air.  On the contrary, the faster the air flows through the core, the less it will increase in temperature on its way through, making the exit temperature and the average cooling air temperature lower.  This increases the differential between the average core temperature and the average air temperature, increasing the heat transfer.  Increasing airflow by speeding up the fan, by providing an improved fan, by providing or improving the fan shroud, by reducing air restrictions in the grille or engine compartment, or by providing recirculation shields to prevent air from bypassing the core, will all improve heat transfer and cooling.

Both of these statements are incorrect.
 
Fact - Increased air/coolant flow increases heat transfer
Fact - Turbulent air increases heat transfer

Both of these statements are incorrect.
 
Fact - Increased air/coolant flow increases heat transfer
Fact - Turbulent air increases heat transfer

the full time cooling comment was actually meant as a joke for when my headgasket goes and i dont feel like changing it:flame:
sorry for the confusion
 
as for the almost stalling thing your having no i dont have that problem with my tbird. im going to take a guess here but when was your last tune up? maybe even a stuck choke. im tired and cant think right now your best bet is to do a search on the site for similar symptoms and see what comes up, or dig thru the archives. replacing the computer from what ive been told is usually a last resort measure for mechanics who cannot solve the problem thru diagnosis(and being an expensive part doesnt help either)
you might want to troubleshoot a few things before going that route.

Both of these statements are incorrect.
 
Fact - Increased air/coolant flow increases heat transfer
Fact - Turbulent air increases heat transfer

I take it then, you've studied a different thermodynamics and heat transfer course than I had to take in college?  That was a long time ago, and I'm not sure, but somehow, I don't think the laws of physics have changed that much since then.
 
If you pass the air too quickly across the cooling tubes, it will not remove/absorb as much heat.
 
If you pass the coolant through the tubes too quickly, not as much heat will be removed.
 

Fast idle on cold engine is achieved with an ICM (Idle Control Motor), not IAC (Idle Air Control) as is the case with later (S)EFI engines.