weird coolant temp issue

[ToddS1971]

I posted last year about this, and I'm gonna post again. Went on a trip this weekend, outside temp 60-65, and on the interstate running 70-75 the temp would go up to 217 then drop back to 195 and slowly creep back up to 217 and back to 195. Logic tells me that's the thermostat opening and closing, but with a 203 thermostat why does it not open until 217? I could see maybe getting to 205-206 maybe, but 217? Around town it'll get to 203 and drop back to 196-97. It's as if the thermostat knows I'm on the interstate and says "nope, you're on the interstate and we're going to 217". If it opens at 203 around town, why does it wait til 217 on interstate? Weird.

 

[Heatheroo]

mine opens at 212F. I see it every morning driving to work: climbs to 212 then drops back to 197 and eventually settles around 203

 

[CamperMike]

Could be active grill shutters opening and then closing. Even if t-stat is open, if airflow is blocked it will be able to heat up.

 

[62Blazer]

You don't get instantaneous cooling the second the thermostat opens. Once it opens the hot coolant needs time to travel through the radiator and cool off. Also, the thermostat isn't exactly a precise temperature switch and could actually open at a slightly higher temp. Temperature gauges may be off by a few degrees also.

 

[ToddS1971]

You don't get instantaneous cooling the second the thermostat opens. Once it opens the hot coolant needs time to travel through the radiator and cool off. Also, the thermostat isn't exactly a precise temperature switch and could actually open at a slightly higher temp. Temperature gauges may be off by a few degrees also.

right...it won't be instantaneous, there's a short lapse, usually about 10 seconds around town to go from 203 to 196-197. The issue is it doesn't appear to be opening at 203 on the interstate...it's 217 before it starts to drop. If it opened at 203 on the interstate, why does it continue to climb until 217?

 

[Bigskyroadglide]

My 2016 did this on Tuesday driving from Montana TO Minnesota. I stopped 2 x and finally removed the grill in a rest area. Twenty minutes later, half the shutters removed, issued solved. Took longer to reinstall grill vs taking shutters out. I chalked it up to lazy shutters or a potential failing shutter motor.

 

[ToddS1971]

So maybe shutters opening and closing. Never considered that. I'll take out a few of them and see if that changes anything.

 

[BuschLatte420]

right...it won't be instantaneous, there's a short lapse, usually about 10 seconds around town to go from 203 to 196-197. The issue is it doesn't appear to be opening at 203 on the interstate...it's 217 before it starts to drop. If it opened at 203 on the interstate, why does it continue to climb until 217?

My 2016 did this on Tuesday driving from Montana TO Minnesota. I stopped 2 x and finally removed the grill in a rest area. Twenty minutes later, half the shutters removed, issued solved. Took longer to reinstall grill vs taking shutters out. I chalked it up to lazy shutters or a potential failing shutter motor.

I wonder if my 2022 classic tradesman has these, seems dumb unless for winter time to warm up faster, other than that if it fails and you need to remove on the side of the road kinda sucks

 

[62Blazer]

right...it won't be instantaneous, there's a short lapse, usually about 10 seconds around town to go from 203 to 196-197. The issue is it doesn't appear to be opening at 203 on the interstate...it's 217 before it starts to drop. If it opened at 203 on the interstate, why does it continue to climb until 217?

Just like I said, it's not instantaneous...that means that the temps don't stop dropping, or even out, the exact second the thermostat opens. The temps are trending up and may continue to trend up before they level off and start cooling. The stat may be opening closer to 203 but the temps could jump to 217 before it gets it under control. Also, the radiator doesn't necessarily have the ability to immediately drop the coolant down, meaning that 217 coolant going in may not be all the way down to 203 or lower when it leaves....it could start at 217 and then drop to 212, then the next pass down to 200, etc....
Sure, maybe the overall system is being "lazy" and something isn't 100%. If your truck does have active grill shutters I could see them being closed on the interstate and cause some more delay in cooling the system........but will also say you are talking about some fairly small temperature swings and really nothing that screams there is an issue.

 

[Burla]

Pre shutter rams even in warm places, the thermo stat usually stays between 203-204 f, on occasion you will see up to 206 to 202 on the evic. It can be 100f here and long freeway drive and it would not be rare to never see over 206f. So the two likely culprits are not only shutters but fan and fan clutch, assuming there isnt gunk preventing t stat to open. There is a group that prefer the pentastar fan with a hemi fan delete.

 

[ToddS1971]

Just like I said, it's not instantaneous...that means that the temps don't stop dropping, or even out, the exact second the thermostat opens. The temps are trending up and may continue to trend up before they level off and start cooling. The stat may be opening closer to 203 but the temps could jump to 217 before it gets it under control. Also, the radiator doesn't necessarily have the ability to immediately drop the coolant down, meaning that 217 coolant going in may not be all the way down to 203 or lower when it leaves....it could start at 217 and then drop to 212, then the next pass down to 200, etc....
Sure, maybe the overall system is being "lazy" and something isn't 100%. If your truck does have active grill shutters I could see them being closed on the interstate and cause some more delay in cooling the system........but will also say you are talking about some fairly small temperature swings and really nothing that screams there is an issue.

In town it's a 10 second lapse from 203 to 196...on the interstate it's more like 2 minutes. 203...205...208...210 etc etc. up to 217. I would think a steady 70 mph wind across the radiator would cool it off quicker than 2 minutes. In town it'***** 203 at a red light and drop to 196 while all the time sitting still. That's no wind across the radiator at all in that scenario except for what the fan could be sucking through.

 

[GTyankee]

choices are

Pentastar Fan
change thermostat to 195°
remove 2 or 3 of the shutters

 

[Dusty]

FYI

The Active Grill Shutters (AGS) run a diagnostic home and reset test every time the vehicle is started. If the shutters do not reach the calibration points (full open to full close) within 2.6 seconds, the PCM will declare a U11E9 fault and a Check Engine message will be displayed. The default position of the AGS is OPEN.

(Unfortunately, an Active Air Dam fault is shared on the same LIN bus signal circuit and will give the same code if in fault mode.)

Its possible that the 217 degree reading is the result of coolant temperature overshoot. The thermostat should be in the fully open position between 100 and 212 F. As coolant temperature continues to build and approaches 212 F, there will be a lag in temperature drop after the cooling fans come on. This is normal.

If there's a problem with a steady state temperature much above 212, there's either a thermostat problem, temperature sensor issue not triggering the cooling fans, or debris/obstruction clogging air flow.

Be advised that the PCM contains a threshold value on coolant and oil temperature and will reduce engine power accordingly.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, factory dual exhaust, 18” wheels. Build Date: 3 June 2018. Now at 87707 miles.

 

[GTyankee]

223°F

Water turns into steam at 212°F. Mixing traditional ethylene glycol antifreeze with water in a 50-50 ratio increases the boiling point to 223°F, which is close to the operating temperature of an engine.

 

[ToddS1971]

So here’s what I tried and it worked! I removed one row of slats and buttoned it back up. Goes to 203-204 then drops to 194, then steadily runs 197-201. I can live with that. And no CEL . I took out row 4 counting the top as row 1 and going down. Figured that was pretty much the middle row. May take out another row this summer when it gets into the 90’s if needed.

 

[hunterdan]

choices are

Pentastar Fan
change thermostat to 195°
remove 2 or 3 of the shutters

Pentastar fan won't work without considerable modifications to the wiring. 3.7V6 out of the 09-12 trucks is bolt in/plug in.

 

[hunterdan]

As has been stated already, the shutters will cause the temps to creep up when cruising at highway speeds. The shutters close to maximize mpg, but open a few minutes once the temps hit 218-220. Even if you do a 180 thermostat, but leave the shutters, you'll never realize the benefits of the lower temps. Bypassing the shutters is easy and cheap, and opens up a whole lot of room behind the grille if you removed them.

 

[jeffburch69]

Mine is doing that now but it will get up to 221 sometimes before the thermostat opens.