.......why not make it run even hotter......put a 25 lb cap on, that way it would run even cleaner, make monster power and maybe get 30+ mpg. LOL

 

235 isn't too hot but its well above normal operating temp. Cooler engines actually build less sludge because the oil doesn't break down as quickly. They build more power because cooler engines have a cooler and denser air charge in the cylinder allowing the engine to burn more fuel. A cooler engine is less fuel efficient because of that same reason. Engines are tuned to be more efficient at around 195-205.

 

If your Jeep 4.0 is running at 235, something is WRONG with your cooling system.

Even though it may not actually be boiling over at 235 it absolutely fits the definition of overheating. Never tolerate those kinds of running temperatures or you're headed towards big trouble.

There is no actual "spec" for running temperature, but the vast majority of 4.0 engines should and do run in the 200-210 farenheit zone.

And if you're running an 00-01 with the infamous 0331 cylinder head, 235 degrees is probably plenty hot to crack that head, as it is susceptible to cracking when run hot.

 

I don't think anything is wrong with his XJ......he just has the efan controller set at 235.......at least that's what I gather from his post #29.

 

Sorry; I missed that post.

I'd still take a bit of fan cycling on the trail and set the fans to come on a little sooner, but to each their own.

And you'd never want to see 235 on a regular basis with an 00-01, that 0331 head would crack for sure.

 

+1000, couldn't agree more.