[DSmith]

2018 WB Challenger, 11K miles.
So here is a weird thing I just noticed this past week. When I start the car, it will take about 10 minutes of normal driving to get up to operating temp around 200 degrees. The problem is the temp keeps slowly rising to between 230 and last night it hit 237. It will hold on that temp for approx 20 seconds, then quickly fall back to 200 degrees. As if something (fans, coolant circulation?) is triggered and lowers the temp back to normal range. It will hold on 200 briefly, then slowly start to rise again to 215 before something is again triggered sending it quickly back to 200. It will not go above 215 again but will continue to go up and quickly back down without ever just holding on the lower temp. My other hellcat never did this. It would rise to just below the center hash mark and stay there. This pattern is present now every time I take the car out. Outside temp makes no difference.
Has anyone experienced this? Perhaps a faulty thermostat? Its going to the dealer next week. They have pre-ordered
a thermo.

 

[Parshooter]

Are your high temps happening when sitting still and the lower temps when moving?

 

[DSmith]

The high temp last night of 237 was on the highway at 65mph and 40 degrees outside. It does not seem to matter whether or not I am in stop and go or cruising. It does this same cycle every time.

 

[Blickie]

The high temp last night of 237 was on the highway at 65mph and 40 degrees outside. It does not seem matter whether or not I am in stop and go or cruising. It does this same cycle every time.

Thermostat?

 

[plo231]

I had higher temps, in the 220’s, so not as high as you. I pulled the thermostat to install a 190 and found the thermostat broken in half. Haven’t had the problem since. Mine is a 2019 REWB.

 

[DSmith]

Thermostat?

I'm hoping it is something simple like that.

 

[DSmith]

I had higher temps, in the 220’s, so not as high as you. I pulled the thermostat to install a 190 and found the thermostat broken in half. Haven’t had the problem since. Mine is a 2019 REWB.

Oh wow...ok. If I install a 190 will it void the balance of my warranty? What brand did you use?

 

[Blickie]

Oh wow...ok. If I install a 190 will it void the balance of my warranty? What brand did you use?

Stick with Factory OE Stat...

 

[DSmith]

Stick with Factory OE Stat...

OK will do.....have read about stats tripping codes etc......

 

[Dennis H]

Characteristic of an air bubble in the system.

 

[moparjim]

A 180 can trip a code when it's cold.
I ran a 190 and never had a code caused by it when I was stock.

 

[BigDaddyEureka]

Thermostat?

Characteristic of an air bubble in the system.

These two right here. Possibly both. Don't panic.

 

[Xylander]

I'd drain and flush the coolant system then replace the thermostat. It's been 4 years, a good flush won't hurt anything. Just pray it isn't the water pump acting up

 

[Sarna March]

If it's under warranty, isn't it a free repair?

 

[JBS$]

Check the actual temp of your motor and compare with the gage. Could be a sending unit (cheap fix) issue.

 

[DSmith]

Thanks to everyone who chimed in. Today was the day it went to the dealer and sure enough the thermostat was broken (came out in 2 pieces). The copper collar is cracked where it attaches to the receiver so it was sort of floating around where it should have been locked in place. Maybe this explains the fluctuations in temp? Who knows. The tech flushed the coolant system while he was at it and she is back to normal.

 

[plo231]

Mine looked the same when I pulled it out. Glad you got it sorted!

 

[DSmith]

If it's under warranty, isn't it a free repair?

It would have been but was out of the 3yr time limit back in June. Cost me $500 total......

 

[Blickie]

It would have been but was out of the 3yr time limit back in June. Cost me $500 total......

Many here criticize Extended Warranties, but here it is...

Glad it was an easy fix.

Antifreeze was 5+ years old; great time to flush and fill both systems, engine & intercooler.

Best!

 

[REDEYE]

It would have been but was out of the 3yr time limit back in June. Cost me $500 total......

Power train (thermostat is part of the power train) is 5y 60000miles on a 2018…