Odd High Eng Temp reading 4.0L 2000 Classic XJ - JeepForum.com
 
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post #1 of 10 Old 04-17-2017, 09:08 AM Thread Starter
CLASSIC2000MST
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Xj Odd High Eng Temp reading 4.0L 2000 Classic XJ

Have a mystery on my hands.... wondering if anyone might have a good clue for me.

2000 Jeep Cherokee Classic ( XJ ) 4x4 4L engine.

Symptoms....
After several hours of stop and go driving, check gauge light illuminated and eng temp read 240 degrees. Hung a U turn to pull over and temp gauge went to normal ( 210 degrees ). Started down the road again and at a long stop light it happened again but it did not go to normal. Parked car . Popped the hood...No overheating, no rough running engine etc. No smell of coolant or burning. Coolant reservoir was normal. Fluid normal color. No leaks .

Next day started car... in 10 minutes reached normal op temp 210 degrees.... secondary cooling fan came on as normal. I watched the temp gauge for the next 20 minutes and it never got over 220 degrees.

This does not sound like a thermostat... after driving several hours it would have overheated much sooner than the gauge indication. Secondary fan kicked on at the right time. Could this be the temp sensor? temp relay? I have trouble thinking it is the pump.

Your thoughts please.

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post #2 of 10 Old 04-17-2017, 11:10 AM
CJ7-Tim
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Thermostats are cheap and easy. If it is more than 2-3 years old, install a new one, either a Stant Premium, or genuine Jeep.


Overheating at idle, in stop n go traffic, and/or on the 4x4 trials, usually should make one suspect a worn out mechanical fan clutch.

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post #3 of 10 Old 04-17-2017, 11:46 AM
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Quote:
Originally Posted by CJ7-Tim View Post
Thermostats are cheap and easy. If it is more than 2-3 years old, install a new one, either a Stant Premium, or genuine Jeep.

Overheating at idle, in stop n go traffic, and/or on the 4x4 trials, usually should make one suspect a worn out mechanical fan clutch.
Agreed with Tim. Also, the temp gauge tends to jump when there's actual steam in the system. So the liquid temp can be 225, but the gauge pegs out. That's still not good, especially for your 0331 head which is prone to crack when overheated, but it explains suddenly jumping high and going back to around 220 after just a brief cooldown period.

Consider doing a chemical flush or two of the system while you're checking the stat and/or the mechanical fan clutch. The XJ's cooling system doesn't have much headroom and really doesn't do well when it's allowed to get clogged. I do a chem flush every other year on my 01, just the basic prestone stuff you can get at a parts store.

BTW if you have a NAPA near you, their store brand "premium" thermostats are degraded stant premium units, so you can grab one cheap without having to wait for online shipping or whatever. Make sure you grab the housing gasket, too.

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post #4 of 10 Old 04-17-2017, 04:23 PM Thread Starter
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Many thanks for the ideas......... So here is what I did and it seemed to fix the problem... ... After chewing on the possibilities I decided to try the " simple stuff " first. Changed the thermostat, the temp sensor and radiator cap because it was easy to do. The thermostat was listed at 195 degrees. It took 15 minutes to get up to 210 degrees... and it stayed there for another 10 minutes before the secondary fan kicked it. Then I took it out on the road. After 30 minutes on the road it never got higher than 220 degrees. My guts tell me it was an electrical issue related to that old sensor. But it could also have been the thermostat being old and not opening as it should.... or both. Either way, I have put 100 miles on it since then with no issues. Crossing my fingers that this really solved the problem.
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post #5 of 10 Old 04-17-2017, 04:35 PM
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That didn't take long, Classic2000mst ...you got right on it today.
Hope you're at a solution.
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post #6 of 10 Old 04-17-2017, 04:37 PM
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Quote:
Originally Posted by CLASSIC2000MST View Post
Many thanks for the ideas......... So here is what I did and it seemed to fix the problem... ... After chewing on the possibilities I decided to try the " simple stuff " first. Changed the thermostat, the temp sensor and radiator cap because it was easy to do. The thermostat was listed at 195 degrees. It took 15 minutes to get up to 210 degrees... and it stayed there for another 10 minutes before the secondary fan kicked it. Then I took it out on the road. After 30 minutes on the road it never got higher than 220 degrees. My guts tell me it was an electrical issue related to that old sensor. But it could also have been the thermostat being old and not opening as it should.... or both. Either way, I have put 100 miles on it since then with no issues. Crossing my fingers that this really solved the problem.
well done.

I'd still suggest that flush when you get time, though. 220's pretty warm for this early in the year, even as a peak in traffic.

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post #7 of 10 Old 04-18-2017, 05:02 PM Thread Starter
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Now on to the next project..... replacing the sagging head liner. Somehow I don't think that will be much fun.
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post #8 of 10 Old 04-18-2017, 05:43 PM
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Now on to the next project..... replacing the sagging head liner. Somehow I don't think that will be much fun.
It's really not bad. Make sure you get ALL the old foam scraped off the old board so the new adhesive has a good hold and it's fairly simple.

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post #9 of 10 Old 04-25-2017, 06:02 PM Thread Starter
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Question..... what do you think of not replacing the foam and the liner ?. I read one post about a guy who just cleaned it completely and then painted it. Seems a heck of a lot easier..... but then the question will be noise. Will giving up the liner and the foam make for a noisy ride?
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post #10 of 10 Old 04-25-2017, 06:47 PM
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Question..... what do you think of not replacing the foam and the liner ?. I read one post about a guy who just cleaned it completely and then painted it. Seems a heck of a lot easier..... but then the question will be noise. Will giving up the liner and the foam make for a noisy ride?
I bedlined mine, not really any noticeable difference.

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