Coolant Temperature Fluctuation, why does this happen?

Davidloveshishemi · Dec 30, 2021

It seems like all Ram 1500's coolant temperatures fluctuate, and I know the active shutters warm the truck up faster but why the wide temperature range? I know its part of it and thats just the way the trucks are. But I have never got a reason why.

Again, I know it isnt a big deal but any explanation would be greatly appreciated. Seems like mine and everyone elses has done it since day one, thought I would ask.

Thanks In Advance!

Burla · Dec 30, 2021

You have to mention the temps man.

Most likely t-stat stuck. OEM should run around 203-204 all the time when warm. If the truck working hard could be higher, but wont fluctuate unless something else wrong.

Davidloveshishemi · Dec 30, 2021

From 194-210, with an average of 203. Took it to the dealership, no issues. Thought the coolant was low and they ran a pressure test, nothing. They filled it back up and its fine, but its always had the temperature fluctuations, along with everyone else I have asked.

NOV87 · Dec 30, 2021

That's how mine fluctuates too

BadHemi2014 · Dec 30, 2021

Sounds like mine, seems pretty normal to me. Mine doesn't have the active shutters. When 1st driving will get to 210 or so, then drops to like 195, then hovers around 203 but still fluctuates between 195ish and 205ish. New heater core, hoses, thermostat, rad cap.

I forget the location of the coolant temp sensor on these trucks? That might have something to do with it. I assume cooled coolant from radiator flows past sensor, thermostat shuts, coolant warms up, thermostat opens etc. Normal cycle. If it fluctuates more than that, runs over 203 all the time or doesn't warm up, then you have a problem.

turkeybird56 · Dec 30, 2021

Burla said:
You have to mention the temps man.

Most likely t-stat stuck. OEM should run around 203-204 all the time when warm. If the truck working hard could be higher, but wont fluctuate unless something else wrong.

Yep, in that range and sometimes up and down, depending if I am towing and also what time of year here. In Aug-Sept we could get weeks of over 100 F temps.

Burla · Dec 30, 2021

Mine never fluctuates 2010 ram, almost religiously hovers 203-204, never drops below 203/2 when warm, and I never seen it above 206f. Having said that I wouldnt be overly worried if it did it with only 10f swings, so I had no idea some rams did this. It probably isnt t stat then, that is what you get when you post the temps. The temp is dropping 10f lower then t stat opens, and is well over what you would expect with an open t stat at that temp, so something else is at play would be my guess. Maybe just a gauge reading, maybe faulty maybe not, but nothing really to worry about. t stat is cheap enough next time you flush coolant maybe replace it, see it anything happens, worth knowing for sure anyhow.

caulk04 · Dec 30, 2021

How long are you driving?

I tend to see the same range mentioned above. Up to maybe 210, down to ~195 and bounce around there to 201-203 until it finally equalizes at the 201-203.

It doesn't fully equalize until 30 minutes or so, rural driving.

Davidloveshishemi · Dec 30, 2021

caulk04 said:
How long are you driving?

I tend to see the same range mentioned above. Up to maybe 210, down to ~195 and bounce around there to 201-203 until it finally equalizes at the 201-203.

It doesn't fully equalize until 30 minutes or so, rural driving.

Thats basically what mine does, once I have driven for 30 minutes or so it evens out to between 201-203. It just takes that long for everything to warm up. Sounds normal according to what everyone else is seeing. Thank you again!

GTyankee · Dec 30, 2021

looking straight at your 5.7l water pump

at the top left, you should see a plug screwed into the pump
That plug is for releasing AIR from the system, so Air Bleeding Plug
Now look at the right side of the water pump, if you notice the fitting & the wires, that can also be used for bleeding the cooling system, but it is actually the Temperature Sensor

You don't have to have the engine running when you use either the water pump plug or the Temperature sensor to get the air out of the system.

Motorcity Mechanic on air bleeding the hemi coolant system

More than one way to bleed a Hemi coolant system

Please use the following link when ever using Amazon.com. Any purchases you make on Amazon will help support this channel.http://amzn.to/2mALgqSQuick Tip: 5....

www.youtube.com

Colt4thHorseman · Apr 28, 2022

I wanted just to state an observation on my 2017 Ram 1500, 5.7 L, I also have a temperature fluxuation on long hauls, especially at higher speeds and long hill climbing.
The coolant temperature slowly rises to 220 degrees F than quickly drops to about 192 degrees F. Then repeats. Lower speeds it stays steady.
At first I thought maybe the cooling system had a problem, maybe the thermostat was sticking.
Then I started to read more about the active grill shutters (AGS) that open when the engine coolant temp gets a certain predetermined temperature. I suspect the AGS will open briefly at higher speeds to reduce coolant temperatures and then close again.
I concluded, this was a normal operating condition of the engine and was not a problem.

theclassic · Nov 26, 2022

Assuming your truck has active grills shutters. Check this out.

Active Grill Shutter "Partial Removal" Temperatures

Hello all. I am well aware that this information is already on other threads. After reading them the few threads that had some good info I decided to post my findings here and what I did. I figured the more places the info can be found the better. The truck New 2021 Ram 1500 Classic, 5.7l...

www.ramforum.com

Colt4thHorseman · Nov 26, 2022

theclassic said:
Assuming your truck has active grills shutters. Check this out.

Active Grill Shutter "Partial Removal" Temperatures

Hello all. I am well aware that this information is already on other threads. After reading them the few threads that had some good info I decided to post my findings here and what I did. I figured the more places the info can be found the better. The truck New 2021 Ram 1500 Classic, 5.7l...

www.ramforum.com

Mine did the same thing until I removed some of the shutters.
The temperature stays pretty constant now.

Coolant Temperature Fluctuation, why does this happen?

Davidloveshishemi

Senior Member

Burla

Senior Member

Davidloveshishemi

Senior Member

NOV87

Senior Member

BadHemi2014

Senior Member

turkeybird56

Military Vet 1976-1996 Retired US Army

Burla

Senior Member

caulk04

Senior Member

Davidloveshishemi

Senior Member

GTyankee

Senior Member

More than one way to bleed a Hemi coolant system

Colt4thHorseman

Member

theclassic

Junior Member

Active Grill Shutter "Partial Removal" Temperatures

Colt4thHorseman

Member

Active Grill Shutter "Partial Removal" Temperatures

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