So its been around 100 degrees here and humidity makes it feel like 115. My Jeep is running temps around 215 and not hotter than that. The ac is not on because it doesn't work and the coolant is full. The pressure cap seems to hold pressure and there is coolant flow. My question is, how warm do these 4.0L engines run normally? I am thinking about changing the T-Stat and seeing what happens. Let me know what you think. Thanks a bunch.

 

Mine always runs between 200 and 220.

 

I run at 210 on a normal day, and around 215 on a really hot day. Your sounds normal to me, XJs always run hot.

 

4.0s are designed to run at 210. I would say 220 is okay but not 230 and up.

 

I had the same concern..good to know the xj's just run hot!!

 

as long as it spikes there and doesnt stay there anything under 240 is okay but indicates you have problems. 250+ is when your idiot light comes on or your gauge goes into the red.

but as stated 215 is fine.

 

^^X2

 

Good to know guys. Thanks, never knew they ran this hot, seems to hot to me, I'm used to my diesel running 170.

 

Changing out a properly functioning t'stat for a lower temp t'stat THIS TIME OF YEAR will probably do nothing.....6 mos from now, yes.

 

wrong.....

you actual cause more damage to the engine as the engine takes longer to warm up and the most wear and tear on the engine is during warm up.

there are lots and lots of articles about it as well. never change out your tstat. always run a 195*

 

I heard 4.0s are designed to run at 210/215 area so I'm sure youre all good.

I hate it. but I dont think its a problem at all

x2

 

I have 195 thermo in mine and it stays around that when I drive around town and on the open road. I had a 185 in it but i changed it when i replaced the water pump. If I'm sitting in traffic now in the heat it'll go up past 210 and come back down when I start getting cool air runnin through everything

 

Yeah mine will also do that too

 

that means either your clutch fan is worn out and you need a new one (the WJ one is a HD upgrade) or your electric fan is not kicking on.

electric fan should kick on at 218

 

Verify, verify. Good data is important here.

The first thing I do with a temp question is to use an infrared point and shoot thermometer pointed directly at the thermostat of a hot engine. Then you'll know.

It is NOT uncommon to have some inaccuracy between the coolant temp sensor and the gauge.

And if you find inaccuracy, replacing that coolant temp sensor is job #1.

The e-fan comes on at about 217. If all cooling system components are working properly and you're not wheelin, you should be able to stay at 210 or lower on the 4.0

If you're not able to, something isn't keeping up. Water pump, radiator, radiator cap, fan clutch, serpentine belt that drives the water pump, thermostat.

Dollar for dollar, there is NO better money spent, than that spent on cooling system maintenance.