Engine temps when cold outside?

[buckeyexx]

What coolant temp with the 6.4 is everybody running at when it’s say in the 20-30 degree mark? I’m asking because I have yet to see my temperature get above 185. This is while driving around town and driving on the freeway for an hour drive. And when it gets up to that point it stays there. Never goes up or down. Maybe this is normal for this motor but when I had my 5.7 I know the temps would bounce between 195 and 205. Just thought I would be seeing higher coolant temps but maybe not a big deal. Just want to see what your all thoughts are. Time for a new thermostat maybe? Thanks


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[62Blazer]

Regardless of the outside temperature the engine temp should run right about the same. It is controlled by the thermostat, and the engine should always run up to the the thermostat temperature regardless of being -20F or 120F out.......if something is wrong with the cooling system an engine can still overheat even if it's extremely cold outside.

 

[buckeyexx]

Regardless of the outside temperature the engine temp should run right about the same. It is controlled by the thermostat, and the engine should always run up to the the thermostat temperature regardless of being -20F or 120F out.......if something is wrong with the cooling system an engine can still overheat even if it's extremely cold outside.

I’m very aware of an engine can still overheat no matter the temp outside. Not having an issue overheating but instead maybe not getting up to the normal operating temp. I may not even have an issue at all but I’ve never seen an engine run at 185 and and stay there no matter the temp outside.

I know these thermostats are pcm controlled and I have never dealt with them so it’s all new to me and maybe normal.


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[SouthTexan]

Hmm, that is odd. Temps should fluctuate slightly(+/ 5F) as the thermostat opens and closes. Maybe your thermostat is stuck in an open or slightly position.

 

[buckeyexx]

Hmm, that is odd. Temps should fluctuate slightly(+/ 5F) as the thermostat opens and closes. Maybe your thermostat is stuck in an open or slightly position.

That’s kinda what I was thinking too. It will get to 185 and stay there no matter the rpm’s and load on it. That’s why I’m hoping somebody with same engine can tell me what they are getting with colder temps outside. This is not towing or hauling but just normal driving.


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[68PowerWagon]

Hmm, that is odd. Temps should fluctuate slightly(+/ 5F) as the thermostat opens and closes. Maybe your thermostat is stuck in an open or slightly position.

^^^ Most likely this. There has been a few guys on here that have reported thermostats sticking open. At those ambient temps mine bounces from 185-215. You can literally see when the thermostat opens & closes. I have never seen a system cycle this drastically. It's a good thing... means the system is pretty large & cools very well.

 

[buckeyexx]

^^^ Most likely this. There has been a few guys on here that have reported thermostats sticking open. At those ambient temps mine bounces from 185-215. You can literally see when the thermostat opens & closes. I have never seen a system cycle this drastically. It's a good thing... means the system is pretty large & cools very well.

Yep think so too. I connected my JScan app to it while it was running to see what temp it was showing. Not sure which one is not reading correct but the app was showing about 7 degrees lower at 178 for some reason. Either way it is definitely not getting up to normal temps. Pretty easy to change so I’ll just do it. Can’t hurt anything.


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[Hd74ica]

Michigan thumb cold outside and my 6.4 gets up to about 214 then drops some when the thermostat opens (I assume.)

 

[wyo2track]

My 6.4 coolant temps will fluctuate at least 10 degrees. It'll run up to over 200 then it will back down and fluctuate over approx. 10-15 degrees driving normally in those kind of temps.

 

[bigdodge]

Your thermostat needs changed. It's stuck open. Mine would only get to 185 just out of the blue one day. Changed it and it's normally about 215 now. These thermostats army computer controlled though. It's just a regular Thermo with a big Temp sensor

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[El Huapo]

Since you're not going above the boiling point, you could stick a thermometer into the coolant at the cap before starting it up and watch it, comparing to the dash readout...? Now it won't be kept under pressure so you need to keep a close eye on it.
What are the standard thermostat values in those engines? 195F?
BTW: Having had a couple of failures of brand-new thermostats, I started putting any new one into a pot of water on the stove with a regular thermometer to see the damn thing actually open when it should.

 

[bengreen79]

I had the same problem with my 6.4. Replacing the thermostat and ECT sensor assembly fixed it.




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[buckeyexx]

After calling 3 different dealerships I finally found one. Had to drive a little further to get it but $112.00 later and an hour of driving I have it. Wanted to make sure to get an oem thermostat since really it isn’t much more than an aftermarket one.
Going to flush the heater core while I’m at it. Suppose to be decent weather here on Sunday so I’ll wait till then to tackle it. Thanks for all the replies.


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[buckeyexx]

Got the new thermostat put in today. It was no to bad of a job really. The truck is now reaching 216-217 before the thermostat opens and comes back down to around 200 or so. Thanks for all the replies!


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[olyelr]

Got the new thermostat put in today. It was no to bad of a job really. The truck is now reaching 216-217 before the thermostat opens and comes back down to around 200 or so. Thanks for all the replies!


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Yep that sounds about right as far as temps go.

Great job!

 

[GsRAM]

Sorry I'm late to this but mine has run right around 200-215 full hot since day 1. Glad to hear you got yours fixed

 

[Oilbrnr]

Got the new thermostat put in today. It was no to bad of a job really. The truck is now reaching 216-217 before the thermostat opens and comes back down to around 200 or so. Thanks for all the replies!
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I've had Mopar replacement sitting on the shelf now for a couple of months. Back in February I noticed while driving from Phoenix to Flagstaff my temp gauge reading below normal. Since I have the Poverty Package on my PW, I switched to the digital temp: 185* (outside temp at the time was 32*) Normally, I'd see 210*. Milage too was WAY down, suspect because it wasn't in closed loop though I'm not sure what the temp threshold is.

Odd thing, at lower speed around town driving, temps would stay right around 210*. I don't think it is the actual sensor (as noted above in this thread, the thermostat housing incases the temp sender, not a controlled device) as I can feel the temp of the air from the heater change as the thermo makes swings from 200+ to 185*

buckeyexx, I haven't really looked yet, but what did you do about purging the air out of the coolant loop? I watched a YT about changing the stat, but the guy really didn't mention too much about that.

 

[buckeyexx]

I've had Mopar replacement sitting on the shelf now for a couple of months. Back in February I noticed while driving from Phoenix to Flagstaff my temp gauge reading below normal. Since I have the Poverty Package on my PW, I switched to the digital temp: 185* (outside temp at the time was 32*) Normally, I'd see 210*. Milage too was WAY down, suspect because it wasn't in closed loop though I'm not sure what the temp threshold is.

Odd thing, at lower speed around town driving, temps would stay right around 210*. I don't think it is the actual sensor (as noted above in this thread, the thermostat housing incases the temp sender, not a controlled device) as I can feel the temp of the air from the heater change as the thermo makes swings from 200+ to 185*

buckeyexx, I haven't really looked yet, but what did you do about purging the air out of the coolant loop? I watched a YT about changing the stat, but the guy really didn't mention too much about that.

The only thing I done to purge the air was to leave the cap off the tank. I let it warm up for a good 25-30 min while the coolant sucked down into the cooing system and just topped it off as it went down. I probably lost a little over a gallon.


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