Thermostat shutter war

[Mcjoneszin]

New 2024 2500 6.4 Hemi owner .. recently on a road trip mine starting cycling up and down between 230 and and 180.. like the shutters and thermostat were at war. This was on the flat highway with no load and cruise set at 72. It did this a few time on the trip.. it will do this cycle about about 10 times fairly rapidly, straight up and straight down and back again. I have removed the top 2 shutters and it hasn't done it since. now it runs 213/217 all the time.. Anyone have ideas or same issue?

 

[oppizzippo]

I've seen mine get as high as 230, but never noticed the up-down you saw. When out west at 5000+ feet and 90F outside it would spike around 230 and come back down to 220. I recently removed the top row of shutters and put some tape across the top of the radiator to the front to try to avoid hot air from coming from the radiator into the air intake. So far, under most conditions, it's 5F over ambient, whereas before, I'd normally see 10+ F over ambient and as high as 20F in high altitude. I use a Banks iDash to monitor all the important temps.

 

[Mcjoneszin]

This is rapid temp swings at no load on flat freeway. it will go from 230 down to 185 in about 10 seconds and back up to 230 and it will do this cycle 10 or 15 time before settling.. Dealer say its normal of course, BS. 45 degree swing in 10/15 seconds cant be any good for machined clearances.. the dealer did pressure check and bleed air and found no problems of course.

She runs the coolest when pushed under load, grade or towing, 200/210

Runs the hottest slow 4x4 220/230.

I also have iDash .. runs +2 intake down the highway, I do get some heat soak around town though..

 

[H3LZSN1P3R]

Would be a faulty temp sensor if anything id guess because there is no way in hell its jumping up and down that fast

 

[Poolmonkey]

Would be a faulty temp sensor if anything id guess because there is no way in hell its jumping up and down that fast

Yep…it can’t cool 40*+ that fast no matter what.
These trucks have a temp sensor in the head?…a bad exhaust valve can cause huge swings fast if so, but usually “hot” at high RPM and lower reading at low….
I would try to get a laser therm on the water neck while the truck is supposedly hot, might not be easy if the swings happen so fast and since it isn’t doing it anymore.
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[Enve46]

If I remember correctly my PW 6.4 would do temp swings like that but not as significant. Usually would see 215ish to 190s and back again but this was pretty consistent with the 6.2 hellcat engines I have experience with.