BeaglesXJ

I got a question for all you jeepers on here. The temp guage in my jeep wont get to 210 even when I go on trips. In fact, it wont even get past 120. Is this a sign that my thermostat is going or what? And could this effect mpg at all?

-Ryan

99redclassic

I had the same thing happen to me a few months back. Replaced the thermostat and it went back to normal. Replacing the thermostat should fix your problem. I'm not sure about gas mileage with it, I felt like I was getting robbed a little bit but not enough to worry about.

spiceman

it might effect your gas mileage, if it stays really cold, and its throwin in extra gas because the ecu still thinks that you're on a cold startup. not sure exactly how the computer in these jeeps figures that out. if its something as simple as just checking water temp.. it couuld...

freegdr

coolantemp sensor signals when up to operating temp to ecu

djb383

Does your heater work? T-stat could be stuck open. If heater works, then I'd suspect bad sensor/wiring/electrical.

tjwalker

How long has it been since the thermostat on this engine was replaced?

A t-stat is a suspect for sure.

I buy my stats directly from Jeep and also like the Stant SuperStat.

Whatever you do, stay away from no-name el-cheapo thermostats, often available on ebay. They are absolute junk.

Go with the 195 degree stat.

BeaglesXJ

Yes my heater works but it doesnt get real hot at all in the cab.

I dont think it has ever been replaced. Its a 98 with just under 150,000 miles on it and Ive owned it for a little over a year now.

I think Im going to replace it tomorrow with a 195* stat from napa and see if it helps at all.

DeathWobble

Yup sounds like you need to replace that sucker. They don't cost that much anyway. Should get a new gasket for it too so there's no leaks

JrRifleCoach

My bet is you'll find the original laying in pieces.

tjwalker

I've seen that before too. If it has 150k on it, I think that is a good long service life huh?

How about changing coolant? Has that been done more frequently? Please say yes! If there is any doubt whatsoever, you must perform a coolant flush. Use conventional (green coolant) at a 50-50 mix.

Always a good time to review other things like radiator cap ($5.00) and hoses. These parts are cheap, often overlooked and can lead to bigger problems.

BeaglesXJ

I have never changed the coolant since ive owned it for about a year now. But I do believe the previous owner replaced the radiator and the hoses before I bought it from him. He was very good at keeping reciepts for everything he did to it as well as mark the mileage and time at which he replaced these things. As for the 50-50 mix I think Im better off buying the regular antifreezebecause its only $3 more then the 50-50 at napa. but thats just my opinion.

And thanks for the help everyone.

spiceman

it'll end up cheaper because after you mix the pure anti-freeze with water you should have left overs

BeaglesXJ

My thoughts exactly.

akb4

any write up on how to change the thermostat?

BeaglesXJ

Not really. The tstat is located on the front of the block in the upper radiator hose. there is 2 bolts that you need to take off which are really easy to get to. When you undo those bolts you better have a pan to catch all the antifreeze that comes out. The tstat should come right out, if not then get a screw driver and pry it out. make sure so scrape off the old gasket because it may be stuck onto the hose as well as the block. Put the new tstat in with the gasket and bolt the hose back on. Then all you have to do is fill the radiator back up and you should be good to go.