What should our coolant temp be?

[Towncivilian]

What's our coolant temperature once the engine is warmed up? I connected a scan tool for the duration of a 50 mile highway trip and the coolant temp appeared to be around 180 degrees. Is this the correct temperature?

[Chuck Tribolet]

The FSM specs a 170 degree opening temp, so 180 is reasonable. I'll hook my scan tool up on the trip home tonight
and let you know what it says.

[ARKQX33V6]

Depends on the exact mix of water to glycol but 170-190 would be normal. Around the spark plugs and exhaust port is much higher. Cooling has to remove well over 2000 F, but your temp gauge would not move much from center if all is OK.

That's why you have that big heat exchanger out front and by-pass within the thermostat. And that thermostat sees the temperatures where it is located.

Remember when you floored it? With higher RPM your cooling system removes more heat because the engine and transmission add greater amounts of heat by friction and piston explosions occurring more often.

At times of heat distress gaskets burn also.

[Chuck Tribolet]

I hooked up the scanner, then forgot to post the results. It read 177F running at about 50 MPH in fourth gear. When I pulled over to read the numbers, it went up to about 183F. Ambient temperature was about 72F.

[Towncivilian]

Great, thanks for those results. My temps are similar (hovering around 183F on the highway going 75 mph, ~90F ambient), so I will assume my cooling system is working properly at this time.

[ARKQX33V6]

Remember that big air/water heat exchanger up front sees a temperature close to 200F and if you are still only the cooling fan brings in enough air. Moving varies and faster you go, more RPM more combustion, more heat produced more cooling air. In your area 100 degrees is not unusual so you have a 100 degree cooling effect at most and that is at 100%. Our exchangers are not 100%, but they are big, with the temperatures you are getting you are OK.

The best coolant is the cheapest, water, but it has many problems. So we mix glycol with it. You have little need for freezing so you can benefit from water. But you still need anti-freeze because of the rust inhibitors.

Instead of 50/50 try experimenting with it, try 40 % glycol and 60% pure water, you should see better cooling temperatures.

I'm stuck in central Ontario with -40F winter temperatures so my mixture is about 40% water, 60 % glycol with a -50F freeze rating and a ridiculously high boiling point.

If I lived in the Sun belt it would be pure water rust preventative and some anti-freeze to safely get me over the expected cold snaps. It takes time for even water to form ice crystals, but do keep your vehicle safe from freezing.

And I have not discussed the high temperatures that the transmission inputs to the radiator. So when you see a 90 F ambient and about 170-190 F temperature you are doing good.