I know this is exactly opposite to most of the posts on here! But a month or so ago, I had to have my head replaced from cracking due to overheating issues. When it was torn apart, I went ahead and replaced the rad, water pump, T Stat, upper and lower hoses and had the block flushed. The only thing that isn't a stock replacement is the water pump, it's just an upgraded high flow from Murray. Now at least on the temp gauge, I'm reading roughly 150-160 running around town without my e-fan on a toggle switch, on. The only time I get up to normal (about 210) is when I'm in a drive through for a while. How can I get this sucker to run a little hotter and get my gas mileage back up? I know it decreases with it running cooler. (Doesn't it?)

 

Sounds like the Tstat is faulty. What temp is the one you place in it? It has to be 195.

 

I put one of the Ultrafail T Stat's in it, the ones with the two stroke design where if it overheats, it stays stuck open. But yes, a 195.

 

It's almost certainly the t-stat or the gauge. You can test the t-stat in a pot on the stove, auto parts store might loan you an IR temp gun to check the t-stat housing temp.

Being supper over rich can lower the temp sometimes....

 

Now how could I adjust it to make it run leaner? I wish we had an IR gun to loan...I work at O'Reilly's...I hope it might just be the T stat, that's an easy fix.

 

Get the MOPAR stat from a Jeep dealer and replace the fail-safe stat.

 

Those are notorious for failing open.

 

Yeah, I had one do that. I'll never use another one.

UltraFail is a good name for it.

 

52028186 stat from the dealer.

They're made in Israel, not china.......

 

Mine had the same issue with an ultrafail wouldn't hit 210 even when wheeling. Replaced it with a normal 195 problem fixed.

 

May I ask the source that says "it has to be 195"?

 

Until your engine hits 195 it is running in open loop (not using o2 sensor) andfigures out how much gas to inject by guessing off vacuum and something else. Once 195 is reached it uses the o2 to calculate more precisely (closed loop)

 

Oh my.....how the myths/false info continue to be perpetuated on the Internet and in forums.

The facts are, Jeep dealerships sold a 180F 4.0L t-stat and your engine enters "closed" loop within seconds of cold start-up. When the heated O2 reaches operating temp of 600F-650F is when the loop "closes, NOT when/because coolant temp reaches 195.

Folks.......please quit posting this false info.

http://www.picoauto.com/applications/lambda-sensor.html.

 

@ djb383 ... Can you please provide info based on a Jeep OBDII application the verifies your statement? A generic O2 sensor blurb verifies nothing.

 

I've been on this forum for a long time and never heard that and would like some more info