Temp sensor problem? underheating?

Well my CEL came on while I was on the highway Saturday. The temperature was running really low (~160°) I noticed, so i figured it was a thermostat that was stuck open. I went ahead and replaced the thermostat (a 195°), and the check engine light has not reappeared - but the temperature is still odd. It will climb up to about 160 and sometimes while sitting in traffic creep up to 180ish (once so far - and i had the aux fan disconnected via a switch). As soon as I get moving its back down the 160ish range. I'm a little bit thrown off by this as I just put in a t-stat. If the check engine light isnt coming back - then is the temp sensor that sends to my dash-guage off? If the engine hasnt complained by now I'd like to conclude that my guage gets info from a seperate sensor then the engine. (is it the one on the t-stat housing that both get info from? or is that just the guage?) Also, my heat runs nice and toasty... And the engine seems warm as ever to the touch. (ouch) I don't know if my last t-stat went bad the same time my temp sensor went bad - what are the odds? - but its possible right?

ok... i tried another temp sensor, no luck.

what year model?

its a 96XJ (like my handle/ name)

but uh, its a 4.0HO,Aw4.

My bad. didn't read your name close enough I guess. Yes, there is another sensor on the back of the head, driver's side. This is the one that sends the info to the guage. You will have to get the OEM part from the stealership due to some type of calibration. I originally got one from Autozone and it didn't work, but the OEM part (twice the price) worked fine.

any clue how much it Should go for? im always cautious when dealing with the stealership... Temp sensors at the local auto stores run from 15 to 37 dollars.

At the dealer in Chattanooga, it seems like I paid right around 20 bucks for it. The nonworking one from Autozone was 9ish dollars.

ok, now something weirds going on for sure - and i dont think its either sensor. i changed another t-stat just in case (they're cheap so why not try it once more...) and i let the jeep idle in the driveway to heat up. it got up to 210 as normal (but with air bubbles coming from the bottom of the coolant resevoir.) then as it heated up more the aux fan kicked in and brought it back down. operation as usual i figure. i drive it around and it seems to drop a hair low - but still close and in the range of regular operating temp (200ish). anytime i let it sit it would hit 210 tho. this morning im driving and it wont hit 210 while driving. It wont hit 210 period unless I let it sit!! i dont get a CEL though. I'm thinking theres an air bubble somehow trapped inside still... making my temp guage read 160 somehow?? how long does it take an air bubble to work its way out of a system? and am i on the right track? thx for any advice you could offer.

CommandoXJ96 said:

ok, now something weirds going on for sure - and i dont think its either sensor. i changed another t-stat just in case (they're cheap so why not try it once more...) and i let the jeep idle in the driveway to heat up. it got up to 210 as normal (but with air bubbles coming from the bottom of the coolant resevoir.) then as it heated up more the aux fan kicked in and brought it back down. operation as usual i figure. i drive it around and it seems to drop a hair low - but still close and in the range of regular operating temp (200ish). anytime i let it sit it would hit 210 tho. this morning im driving and it wont hit 210 while driving. It wont hit 210 period unless I let it sit!! i dont get a CEL though. I'm thinking theres an air bubble somehow trapped inside still... making my temp guage read 160 somehow?? how long does it take an air bubble to work its way out of a system? and am i on the right track? thx for any advice you could offer.

Click to expand...

Ever get this worked out?

any word on this... I am experiencing the same thing...

Just to let you know ... I got a niehoff temp sensor that didn't work for my gauges. I replaced it with a dealership part ($23), and it worked perfectly.