Running Hot

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Jun 13, 2022
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Location
Austin, Texas
Current Rides
2021 JLU Willys Hemi Swapped
Not sure if this is the right place to post this question, but I wanted to see what everyone is running for coolant temp? Usually, mine is sitting around 204-206 for everyday driving. But when I get it up to highway speeds (75-80), I notice the temp shoots up to around 225-230. Can this motor take that sort of heat?

Thanks in advance!
 
So I paid close attention today during the 30 miles drive. Shortly after cold start, it stayed at 201-204, and on highway then local, it was at 217-219 max.
That's what mine usually runs at. But lately, in TX, it's been hitting 100+, so wondering if the heat is making it run hotter.
 
I'll say the heat plays an role. It's only 80+ here in PA. And I don't have a winch nor bull bar as your profile shows. I guess the airflow is slightly better? Probably no real difference.
One thing I do is checking the radiator regulars and remove the dead bugs from the fins with a 18 gauge wire when I can't get them washed away with garden hose.
 
I'll say the heat plays an role. It's only 80+ here in PA. And I don't have a winch nor bull bar as your profile shows. I guess the airflow is slightly better? Probably no real difference.
One thing I do is checking the radiator regulars and remove the dead bugs from the fins with a 18 gauge wire when I can't get them washed away with garden hose.
I did just take it on a massive road trip and washed it, but didn't think about the radiator. I'll give that a clean tonight and see what comes of it.
 
In Colorado here. 5500’ elevation at home. Typically see 203°-215° running around town. Highway, around here I see 212°-230°. At altitude (10k-14k’), I see 215°-225° at idle and as high as 252° while driving.
This is normal for altitude, but admit, that temp makes me nervous.
The coolant temp however, is always between 190°-220°, pending conditions.
Fortunately, synthetics can take up to 300° before they start breaking down.

I recall my JKUR (3.6) coolant would spike to about 230° at altitude. That made me nervous as hell.

The GC SRT, coolant and oil numbers were similar. Slightly cooler on the oil, however I believe had a better set up to get air through the engine bay.
 
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In Colorado here. 5500’ elevation at home. Typically see 203°-215° running around town. Highway, around here I see 212213°-230°. At altitude (10k-14k’), I see 215°-225° at idle and as high as 252° while driving.
This is normal for altitude, but admit, that temp makes me nervous.
The coolant temp however, is always between 190°-220°, pending conditions.
Fortunately, synthetics can take up to 300° before they start breaking down.

I recall my JKUR (3.6) coolant would spike to about 230° at altitude. That made me nervous as hell.

The GC SRT, coolant and oil numbers were similar. Slightly cooler on the oil, however I believe had a better set up to get air through the engine bay.
So similar numbers for what I am seeing down here in central TX. Out driving around today on side roads and the coolant temp stayed around 203 - 215.

Got on the highway and stayed between 210-230. The 230 part makes me hella nervous but seems that is going to be normal coolant temp.
 
Mine ran similar very warm temps. No idea if it helps with performance, however I added a DSP PCM, Intunei3, 180 t-stat and set fans to 185F. It sits at 185 all the time now and no CELs.
 
Time stamp at 3:39 (20 minutes after start up) was 80mph, 97°f, 26% humidity, varied elevation.
Time stamp at 3:41 (22 minutes) was at 45mph, same Conditions as listed above.
Time stamp at 3:45 (26 minutes) was at idle for 4 minutes, all same conditions.
 

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Modern engines run hot. If you believe what the experts say there are a few reasons. First is fuel economy. A hotter engine with thin oil will get a tiny amount better mileage. Not really noticeable to an individual IMHO. But for a manufacturer paying a fine against the CAFE standards, every little bit counts. Second is emissions, hotter burns cleaner. Burns Out deposits of bad fuel and oil contaminates.

But now there is a fine line between what was designed for temp and “too hot”. And an owner must watch the temps to make sure normal range doesn’t turn into overheated since there is maybe 15-20 degrees between the 2.

All that aside, it is designed to run in the 220s for coolant. 230s are acceptable in many situations. 240s is too hot and requires the driver to intervene to not go into limp mode at 250°. I don’t worry much about oil temps. Really anything below 270° is fine and does boil out condensation to cut down on corrosion.

I can put any modern vehicle into limp mode in normal driving. They are just designed to operate hot as normal and if a couple normal traffic situations happen it will go into limp mode.
 
Modern engines run hot. If you believe what the experts say there are a few reasons. First is fuel economy. A hotter engine with thin oil will get a tiny amount better mileage. Not really noticeable to an individual IMHO. But for a manufacturer paying a fine against the CAFE standards, every little bit counts. Second is emissions, hotter burns cleaner. Burns Out deposits of bad fuel and oil contaminates.

But now there is a fine line between what was designed for temp and “too hot”. And an owner must watch the temps to make sure normal range doesn’t turn into overheated since there is maybe 15-20 degrees between the 2.

All that aside, it is designed to run in the 220s for coolant. 230s are acceptable in many situations. 240s is too hot and requires the driver to intervene to not go into limp mode at 250°. I don’t worry much about oil temps. Really anything below 270° is fine and does boil out condensation to cut down on corrosion.

I can put any modern vehicle into limp mode in normal driving. They are just designed to operate hot as normal and if a couple normal traffic situations happen it will go into limp mode.
Agreed. I've been paying close attention to the temp gauges on a daily basis. 200-220 is the range of coolant temp and it's been very consistent. The oil temp can easily go over 240. The offroad+ mode can pump it a bit more based on my observation.
 
Agreed. I've been paying close attention to the temp gauges on a daily basis. 200-220 is the range of coolant temp and it's been very consistent. The oil temp can easily go over 240. The offroad+ mode can pump it a bit more based on my observation.
The fan turns on low at 226°, if a/c is not on. So in very easy driving 226-228° should be your high.
 
Do they sell an upgraded radiator with the hoses for our 392?
 
Yes, but my experience is it doesn’t help. Only solution that works is updating the fan to turn on at a lower temp.
I have this mod from RPMExtreme (I think) on my JK. It helps A LOT in city and low speed driving, especially when the A/C is on. The temps are much lower, and so is the A/C.

It works with the OEM fan by taping the CAN bus, which is neat. No error lights, etc. Most of their customers are HEMI Jeeps, not sure if 392s though.

It also has a manual Full Fan Speed overdrive switch, which helps it even more.

Where it doesn’t help is at highway speed since the airflow is already there, fan or no fan, and the limiting factor is the cooling system itself. On Jeeps (Wranglers) heat soaking and limited space are always affecting heat exchange.
 
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