4.0L cold weather running temp question???

[cr_the_machinist]

It's pretty cold out here in Michigan and I can't help to notice that my temp gauge is a little over active. It will warm up to normal running temp, then cool down, then warm up, then cool down, and so on. It never gets too cold and the heater blows hot as well. My question is this the sign of an over-active thermostatc or is it normal for it to behave like that in 5*F windy weather?

 

[jmg8550]

could be an over active t-stat. not hard to replace.

 

[cr_the_machinist]

Yeah, thats what I was thinking. I know the coolant in the radiator would be damn cold before it hit the block again but the t-stat should shut when that cooler coolant hits it (and the sending unit), right? Maybe I'm not understanding something but that t-stat is supposed to keep the coolant temp in the engine constant.

Does anyone else have this problem in bone cold weather?

 

[Sevensecondsuv]

That's actually pretty typical. The coolant gets so cold in the radiator that once the t-stat opens, you have a big inrush of really cold coolant and the gauge reads a little cooler. Then the t-stat closes and process starts over.

When it's warmer, you have a much smaller temperature differential between the engine and radiator. Therefore the thermostat is able to find a happy medium between full open and full closed and it just kind of sits there, which is why you see a constant temperature.

I have found that the Stant SuperStat thermostats are more resistant to the open-close winter operation than other cheaper thermostats. So you could put one of them in if you wanted.

 

[cr_the_machinist]

Thanks for the info Sevensecondsuv. I'll have to stop by the Local Shop and track one down.

 

[Stranger ranger]

Check the temp sender connection. Could be loose.

 

[cr_the_machinist]

Yeah, I've even pulled it out to make sure it wasn't covered in boogers.

 

[SoLongStang9499]

I wouldnt worry about it, I replaced mine about a month ago due to a leaking housing. Mine does the exact same thing in cold weather, and i have noticed on warm days it doesnt do it, just like sevensecondsuv said. Its just doing its job.

 

[98blownranger]

it is 25 below today and my truck read the same temp all the way down the highway and city

 

[north44]

Just recently changed my thermostat.

Old thermostat was stuck open, and temp gauge barely moved out of "cold" range, ever - this was in late Dec/08. CEL came on and code read as "coolant not reaching proper operating range" (I paraphrase).

With the new thermostat, engine warms up and temp gauge is steady as a rock - about as exactly half-way between top and bottom of gauge as the eye can tell.

Might be easiest if you just change the thermostat (don't forget to get a new gasket as well) - cheap price to pay for peace of mind - parts were under $20.00 CDN if I recall.

P.S. We're enjoying the same deep freeze as most of the NE States.

 

[fighterpilot]

I have a 4.0L in my 96 4x4 STX SuperCab with a super cooling radiator. I'm in Missouri and it's been pretty cold here this winter. I hooked an external temp gage to it and notice that the engine will heat up to about 195 degrees and then once the the tstat cracks the temp immediately goes down to 165. It will then heat back up to 195 and once it gets the coolant in the radiator warmed up it will steady out about 185-190 degrees while driving. I can play with the heater mixing knob and make that running temp increase up to the 195 if I turn it almost down to cold. The truck will still pump out some heat at this setting.

 

[cr_the_machinist]

Seems like its not worth fiddling with yet. Just wanted to get some input. I'll have to see what the warmer weather brings. If it still keeps it up I'll probably change it. I spent all of my free time today taking the crappy rear shoes off of my truck and putting some better rivited shoes on while the weather was above 32*.