So I have a XJ with a straight six in it and do a decent amount of highway driving. Im from Oregon and the cold weather is killing my mpg. I replaced my radiator during the summer and was doing great since the motor stopped overheating. Anyways, now with the colder weather my jeeps engine when Im going 55-60 mph only gets to a temp between 130 and 150 degrees, when it should be hovering around 200 degrees. Ive tried looking for a grill cover for the jeep, or even better a homebrewed design, but for the time being I have embraced a little bit of my redneck side and used duct tape to make a temp grill cover. Is there anyone who knows of a grill cover for the jeep or has seen a homebrewed one? any info will be much appriciated.

 

Are you sure your temperature sensor is operating correctly? I've driven mine in 15 degree weather for 2 months, and it always got up to 210 degrees.

 

ya, when I replaced the radiator I tested the temperature sensor to make sure it was working before I put the new radiator back in. So the sensor should be fine. Imediatly after replacing the radiator I noticed it cooled the engine much faster then the old one did as well.

 

I've driven my XJs(97 and a 94) in -30 degree weather and still able to hit the 200 easily.

 

thermostat stuck open?

 

for you guys who have driven in 15 and 30 degree weather, have you been going around 60 mph in that? it seems only to happen when I am traveling on the highway.

and how would I know if the thermostat is staying open? take the whole thing appart?

 

My driving was primarily around 50-55mph.

 

I'm up here in NH, yeah mine likes running cool as well. Hangs around 170 - 190 regardless of where, or how I'm driving. Oil pressure drops off a bit too. Even with new oil/wix filter. The OP hangs around 15 or so on idle. Sometimes less... It will peak however during acceleration right at 40.

 

New tsat and just put car board over the radiator behind the grill. Cheap easy and free.

 

Alot of therms have a safety feature where when they over heat they stick open, this could have happened to you. Remove t stat, heat in water to check if it opens, then run under cold to see if it closes. They are cheap enough I just replace them if their suspect. Check yours too see if its stuck open when you remove it, if it is, replace.

 

I agree you shouldn't need the cardboard, you ain't got a diesel with a massive radiator. I live where it gets quite good and mine runs 208 degree in August and in January.

 

I personally did the cardboard trick too. Without it my jeep would run a little too cool. Mind you, I have an aluminium radiator and all, save the heatercore and fans, of my cooling system has been replaced.

And while I didn't test my thermostat, or sensor. I can tell by my gauge while the engine warms up from a cold start, all is normal. But once it gets to around 190, it drops (thermostat opening).

 

So I finally got my thermostat out of my jeep tested it, and it was fine. Do you guys have any other ideas to why my jeep is running so much colder then some of yours? I put a new thermostat in and drove it around town and even on highway and never touched 210. not even 200.

 

Do you have access to a laser thermometer? Shoot it at various places in the cooling system. I'd be curious to know what the real cylinder head and radiator readings are.

 

I'd try resetting the pcm. Lights on/off thing.