How hot is too hot?

KingCarGuyZ

KingCarGuyZ

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Dallas, TX
So I just did a full cooling system overhaul. And have been watching g my temps using an OBD2 gauge (still uses factory pickup but tells you the actual # the PCM is seeing. Not the fancy idiot light on the dash.
I run as follows

about 197-202 done the freeway depending on outside temp
202-204 in city on a cooler day 60-mid 70’s
204-208 on hot days 80’s and 90’s
If I get into traffic I will see 208-210. Drivethrus and other low air flow idle situations raise the temp. (To be expected)

My question is how hot is to hot? I will let the Jeep get to about 212-215. Before I give her some revs. (About 15-1800) and bring her back to 205 Ish. However I’m not really sure if this is necessary the more I read and think about it. I was reading that the factory fan clutch doesn’t lock up until 215*. And the coolant gauge says 210*op. So how hot can she get before I bring her back down? Is 220* fine to idle at? 230,240? Obviously there is a point where you will boil over and risk serious damage. But when should you get concerned.

I would be curious to know those of you that are running a OBD2 gauge or external gauge. What temps do you get. Figured I would ask around before I got all Concerned about nothing and tried to wire up a additional cooling fan or something.

P.S. my whole cooling system is refreshed with OEM parts (aside from the Gates water pump) and is running OE MOPAR coolant. This is the 4.0. I6 and I have a NV3550
 
Here in Arizona where we have temps that sometimes get into the 120s, my engine temps will read slightly over 220 on those days with the A/C on in stop-and-go situations. This is normal of course.
 
Chris said:
Here in Arizona where we have temps that sometimes get into the 120s, my engine temps will read slightly over 220 on those days with the A/C on in stop-and-go situations. This is normal of course.
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Slightly reassuring, on the stock gauge or external?
 
if you see 235-240 might indicate that something is wrong but not always. If you are really getting into it up a big hill or something, that could just be normal, but if you are just cruising along and see these temps, I would start checking into things such as low coolant, bad thermostat or radiator cap etc.
 
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HYRYSC said:
if you see 235-240 might indicate that something is wrong but not always. If you are really getting into it up a big hill or something, that could just be normal, but if you are just cruising along and see these temps, I would start checking into things such as low coolant, bad thermostat or radiator cap etc.
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That's reassuring. ill try and hold back for a little while and see what she keeps herself at. I'll report back if I have any problems with running the higher temps.
 
You're completely overthinking/overworrying this temperature thing. Go by the temperature gauge on the dash, it is accurate enough and will tell you if your engine is running too hot or too cold. There's such a thing as TMI... too much information. :)
 
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By the way, I am not afraid to install aftermarket gauges when warranted. Like my automatic transmission temperature gauge below in front of the shifter. I have installed tachometers, oil pressure, and charging system gauges but the standard TJ temperature gauge is plenty accurate for me. :)

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I wouldn't think twice about it until it's over 220. Above that I'd probably start trying to get it cooler just being proactive (like turning off the a/c). 230+ is where I'm really starting to worry.
 
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