Temp guage acted odd

P

Peter Panagakos

TJ Enthusiast
Joined
Oct 3, 2017
Messages
217
Location
Rio Rancho, NM, United States
I have a 2006 TJ with the 4.0 engine and Auto trans. I recently replaced the radiator (bought a factory one from Jeep Dealership), the water pump, thermostat and the overflow bottle. All has been working quite well. Temp guage stays just south of the 210 mark and has been steady. A few days ago I was driving up a highway I take home from work. When I drive on this road I kill the overdrive because I go right about 45-50 and a bit uphill. I noticed when I drove there last time the temp guage dropped to about the middle of the 2, It went back to 210
when I turned off the highway on to a side street. I put the overdrive back on as I drive 35 on the side roads. I have not seen the guage do this before. It has been normal since. I would appreciate any thought on why it would do that, and if it means anything. I considered that maybe the thermostat opened too much and then went back to normal, but frankly my mechanical knowledge is limited. I'm in New Mexico an it has been hot lately, around 100-102.
 
The gauge on the later TJ's 05-06 I believe are basically like a " green okay " light. I would get or borrow a OBD2 scanner capable of reading operating temperature. I believe anything over 250 deg on a stock engine maybe a potential problem? Also did you change the rad cap when you did the radiator?
 
Did you check your coolant levels after completing the cooling system overhaul? I typically have to go back once all the air is out of the system and add coolant. I agree that you should buy one of those OBD2 scanners so you can monitor temps using actual digital data instead of using the sloppy stock gauge
 
TokenJo said:
The gauge on the later TJ's 05-06 I believe are basically like a " green okay " light. I would get or borrow a OBD2 scanner capable of reading operating temperature. I believe anything over 250 deg on a stock engine maybe a potential problem? Also did you change the rad cap when you did the radiator?
Click to expand...

Pretty much...it's a little bit more than a status as it does show some slight, needle width differences between major changes. Middle of the 2 is probably 185ish, middle of the 0 is about 230.

But if I understand the question correctly, the needle dropped DOWN to middle of the 2, so it's not an overheating issue.
 
Peter Panagakos said:
I have a 2006 TJ with the 4.0 engine and Auto trans. I recently replaced the radiator (bought a factory one from Jeep Dealership), the water pump, thermostat and the overflow bottle. All has been working quite well. Temp guage stays just south of the 210 mark and has been steady. A few days ago I was driving up a highway I take home from work. When I drive on this road I kill the overdrive because I go right about 45-50 and a bit uphill. I noticed when I drove there last time the temp guage dropped to about the middle of the 2, It went back to 210
when I turned off the highway on to a side street. I put the overdrive back on as I drive 35 on the side roads. I have not seen the guage do this before. It has been normal since. I would appreciate any thought on why it would do that, and if it means anything. I considered that maybe the thermostat opened too much and then went back to normal, but frankly my mechanical knowledge is limited. I'm in New Mexico an it has been hot lately, around 100-102.
Click to expand...

Sometimes after a period of very low load (such as coming down a mountain pass) the thermostat will close to keep the coolant temp up, and the coolant in the radiator will cool down to near ambient. When the load comes back and the thermostat opens, the engine takes a radiator full of cold coolant and the coolant temp will dip momentarily. I don't know if this lines up with what you saw, but regardless, a momentary dip down a few degrees isn't anything to be concerned about.
 
  • Like
Reactions: Danarch
Yes, what I saw was a temporary (I mean maybe a minute or so) drop. It did do this after a slow drive through a town called Corrales which takes me to the highway. Then I killed the overdrive and put more load on it going up the highway. You probably right. And yes I burped the cooling system and I make sure the coolant level is correct. I take care of my Jeep better than my other vehicles even though I drive the Jeep much less. Thanks for the input.
 
Top Bottom
Back