I'm not going to get into an argument with everyone but here are the facts.

One month ago I was running the stock thermostat with 50/50 Dexcool and Water Wetter and stock fan settings. My Highway temps were b/n 192 & 194 (before water wetter 198 was my avg.) with it getting up to 220+ in stop and go traffic.

I switched my stock t-stat for a 160 thermostat with no other changes made to the fans or fluid. I am now running a consistent 172 degrees on the highway and of course 220+ in stop and go traffic without my A/C on to run the fans.

Numbers don't lie? Did my coolant temp sensor go , I don't think so. If a thermostat doesn't affect coolant temps without a change in fan settings, etc then I don't know why I'm running cooler temps!

 

The whole controversy appears to me to be a difference of opinion on whether the thermostat or PCM has the maximum control of the system temperature. From what has been posted, it seems that the stat controls and mantains the lowest level the coolant temperature can reach in normal operation while the PCM controls the upper range thru the fans. To solve the dilemma, which one can the engine do without and still operate?

 

The results of your temp drop is exactly what would happen from changing the thermostat to a lower temp rating, obviously because the thermostat is what controls and maintains the eng temp while cruising. But one thing to point out and what I mentioned earlier above is now that youve altered the stock cooling system, the thermostat, with a much lower rating, your thermostat is now staying wide open because its trying to increase the flow in order to cool the engine down to 160 but is unable to because the radiator is too small and is unable to get rid of the heat quickly enough before the coolant re-enters the engine. If you had a DeWitt or whatever aftermarket radiator, you would probably be able to maintain exactly 160, which personally I think is too cold. Or since youre getting all the way down to 172 and if you had a 180 thermostat, you would probably be able to maintain 180 right on the money.

Anyway, with the stock fan settings, your engine is now going to have a spread of about 50-60 degrees temp differences of expanding and contracting. Just something else to think about.

 

Its not really a fair question as to what the engine could do without and still operate. All components are needed at one time or another. The problem with some people is they believe that the thermostat is only used to warm up the engine to a minimum temp and then its totally out of the picture and no longer a factor, which isnt the case. I keep hearing its the equilibrium of this or that, or heat transfer and this and that as if the thermostat isnt even in the system. As long as there is airflow across the radiator, while cruising, the thermostat IS the BRAIN and is controlling the flow of coolant through the system by opening or closing to regulate the flow in order to maintain its temp rating. All I was trying to clarify way above is how the cooling system works in conjunction with the thermostat, radiator, fans, and what happens when people put in lower temp thermostats and why it usually never reaches that particular temp. Mainly because it was designed as a matched system to operate together for that particular temperature range (stock 194). If you drop in a lower thermostat, particularly a 160 thermostat, yes your temps will drop, but unless you modify something else to help it, like the radiator, youre not going to see the temp drop to the rating of the thermostat.

 

The only reason you have a thermostat is so you don't OVERCOOL when the ambient air is very low. Yet I hear this ten times a day when people are trouble shooting cooling issues.

I like the home analogy the best, it really makes you think about it a different way.

It goes like this...if you had a too small air conditioner, it ran continously and it still would not cool the house down, would you change the thermostat on the wall or get a bigger AC unit?

 

All this (threads) is too much to comprehend in one comprehension.

 

Are you trying to say that it's incomprehensible.

 

All I know is that when I put a real radiator in my car, the temps never go over 198 no matter how hot it is outside or how hard I drive the car.
And I run a stock t-stat

 

My gosh people, just run a stocker and be done with it.