I believe I have read on this forum that the temperature gauge is not a direct water temperature reading but a calculated figure. Is that correct and if so can anyone explain it to me. I ask because I recently replaced my orange coolant with yellow coolant and while I had the thermostat out I decided to experiment with a 180* thermostat (MotoRad 655-180). The thermostat seems as high of quality if not better than the factory 195* thermostat. I am just a little surprised by the temperature results. Thank You

 

What did you expect to happen? A thermostat set at a lower temp doesn't make the engine run at a lower temp. It doesn't directly control the operating temperature of your engine like a furnace thermostat. The main reason it's there is to help the engine warm up quickly. At operating temperature, your stock thermostat was already wide open most of the time. Your replacement just opens a minute or two sooner and keeps the engine from warming up as quickly as it was designed to. There's not really any good reason to do this.

 

As I stated above I wanted to experiment, I did not need a good reason. What I expected to see was a predetermined outcome reflected on the instrument cluster temperature reflective to the lower thermostat. This was not the case so it stands to reason maybe this a calculated value based on other parameters not just water temperature. I am not here to argue the merits of thermostats, I am just curios as to how the temperature value is generated.

 

I explained why changing the thermostat doesn't change the operating temperature.

 

I’d imagine the electric radiator fans would have more of an affect on engine temps...

 

That's funny, I have a 180 thermostat in my Merkur XR4Ti and it runs at 180 according to my Autometer coolant temperature gauge.

 

Bingo. The fans control operating temperature depending on the PCM programming. Your thermostat is wide open at 180 but the PCM turns the fans on (when the A/C is off) around 220 and will run them until temp goes down to about 205. The only thing the lower temperature thermostat does is increase warm up time of the engine and the heater.

 

Fans should have little effect if the truck is up to speed.

To truly use a low temp thermostat at low speed or stopped, you will indeed need to lower the temp at which the fans operate.

 

At speed the computer will use the grill shutters to get temp up even with a lower temp thermostat. Engines run more efficiently when they're hot and the computer will do everything it can to get engine temperature up as fast as it can.

 

I miss wrenching on those cars. Such an awesome car to drive.