Normal Thermostat/Temp Behavior?

[Vinny68]

I have a '97 Ranger 2wd with the 4.0L. Replaced the thermostat last year because I wasn't getting any heat in the cab. Now that it is cold again (-8F today on my way to work with wind chill of -20) the truck will get warm and the temp gauge will get to the half way point. However after I come to a stop at a light and accelerate again just up to 30mph or so the temp gauge will drop quickly to the C marking before slowly climbing back to the middle again. It seems like heat is blowing from the vents the whole time this happens. Just curious if this is normal behavior or if it's something I need to check out.

 

[SenorNoob]

I can get heat from the vents before my gauge moves than a couple needle widths. That much travel of the gauge at stop signs seems excessive. Remember it's an electric gauge. What's your voltage gauge doing at the same time if you have one?

 

[Brain75]

the colder it is outside, the colder your water in the radiator will get during the closed period (thermostat shut), suddenly flush that cold water into the engine (thermostat opens) and if the sensor is really sensitive it will swing pretty quickly down... -20 is pretty extreme.

On several of my older cars we had to partially block the front of the radiator (cardboard) to prevent excessive cold (especially the little diesel buick century) when it got sooo brutally cold outside.. otherwise the engine kept getting really cold and the heater even would blow cool from time to time.

FWIW, on my 2nd gen during 40-ish temps a month ago, my gauge only swings between N and O in NOrmal... never down to C and never any higher, I have yet to drive it in this brutal cold we are getting now.

 

[rusty ol ranger]

My 460 will do this in my 97 F250...although not quite to that extreme when its this cold.

Yesterday id watch it get just above the "o" in normal, then drop back to the bottom of the normal band, then crawl back up and repeat.

Im figuring in this cold of temps when the T stat opens the coolant rushing back in is so cold it shuts the t stat again, and it has to heat up and open again.

I wouldnt worry to much