XJ XJ8 / XJR ( X308 ) 1997 - 2003

Overheating no reason?

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Old Oct 8, 2023 | 03:04 PM
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Default Overheating no reason?

I just replaced all four of the O2 sensors in my 2003 XJ8.
After driving it home from the shop, when I got out of the car I noticed the cooling fans had engaged. I hadn’t heard that in a while but thought nothing of it, until they started engaging after every trip no matter how short. So far after three days, the car seemed fine, with the exception of the fans coming on constantly.
Then, yesterday afternoon, after a short 8 mile round trip to a store, on the way home, it redlined. Well I freaked and pulled into the suicide lane to avoid traffic. I sat for about 2 minutes and popped the hood. When I opened it, to my surprise, there was no hisssing, no fluids leaking, no evidence of your typical overheating.
I then got back into the car, started it, and the temp started dropping fairly quickly. At this point I don’t remember the fans, but I know I had turned off the AC. After about 5 minutes I was able to drive the car home (about 3 miles) with no issue. Thinking it may have been some “Jaguar” gremlin fluke, I took the car back out. Well the temp started to creep up slightly after about 10 miles, but then I turned off the AC and that straightened it out almost immediately.
Im at a loss. All fluids look good, cars running like a bear, just can’t explain it.
Any thoughts? Many thanks in advance to all.
 
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Old Oct 8, 2023 | 03:48 PM
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Air pocket in cooling system?
Failing thermostat?

I assume you removed the cooling system reservoir?

Are the air bleed lines back in the correct positions?
 
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Old Oct 8, 2023 | 04:16 PM
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I burped the system and filled from the top,
I didn’t replace the sensors myself, did they need to remove the reservoir? The bleed lines are crossed as they should be
as for the thermostat, I thought of that, could that show the symptoms I described?
thank you Mm you always help me
 
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Old Oct 8, 2023 | 06:48 PM
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The expansion tank would’ve need to be removed. That should’ve been taken care of by the shop.
 
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Old Oct 8, 2023 | 07:08 PM
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Thank you. I’ve checked all connections and all lines. Coolant level is fine, no leaks and lines are correctly cris crossed.
im thinking thermostat. Would like to replace it myself, but I can’t find any tutorial videos on YouTube. I’m assuming I’ll need to remove the triple pipe to get to the thermostat below?
 
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Old Oct 8, 2023 | 07:51 PM
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We replaced DOZENS and DOZENS of thermostats when the AJV8 was introduced.

The AJ6 and AJ16 thermostats failed OPEN but the V8 TMOSTATS failed CLOSED!!!!!!!!!
 
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Old Oct 8, 2023 | 08:05 PM
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Perfect! Thank you so much!
 
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Old Oct 8, 2023 | 08:54 PM
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If you have a plastic thermostat housing, you may want to replace it with an aluminum version.

What happened to the 98’ you had?
 
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Old Oct 8, 2023 | 09:03 PM
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It is aluminum! Thanks for the thought…still have the ‘98!


 
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Old Oct 8, 2023 | 10:23 PM
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Oh, I have a picture of that car too! 😂

I was wondering whose it was as I’ve seen it around before. Now I know. That is a beautiful car! Must’ve been a Canadian import?
 
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Old Oct 9, 2023 | 12:44 AM
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What color is that? It looks darker than Ice Blue but definitely lighter than Sapphire.
 
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Old Oct 9, 2023 | 07:22 AM
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The car is not a Canadian import lol. My old mechanic had it sitting outside his shop one day when I went by to visit him. It was mainly silver, with sage green hood and front quarter panels! I asked him whose it was and he said it was an older customer who had wrecked the front end, and the only parts he could find were the sage replacement’s panels. Long story short, I ended up buying it for $800, and having it custom painted by a friend of mine here in Jacksonville, FL. (Thus that’s why you’ve never seen that color!) …I picked it out of a PMS color book!
Here she is the day I bought it!


 
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Old Oct 9, 2023 | 07:23 AM
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Addicted….where did you snap those pics of my car at? Did we meet?
 
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Old Oct 9, 2023 | 10:11 AM
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Scott, we’ve never met in person. We’ve talked on the phone about 2 1/2 years ago. That pic I took when my buddy and I went over to Matt’s for dinner on Monday September 11. I live just about a mile away from Matt’s. I believe Highhorse put us in touch regarding your 98’. I seem to recall a cruise control issue you had.
 
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Old Oct 9, 2023 | 10:17 AM
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That is correct! Okay cool. The cruise control ended up being two vacuum lines switched, so simple yet befuddling. I eat at Matt’s at least twice a month with my family, they live in Hidden Hills. Probably seen my black ‘03 there too. Thank you!
 
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Old Oct 9, 2023 | 02:37 PM
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Default coolant fans

Originally Posted by 3timejag
I just replaced all four of the O2 sensors in my 2003 XJ8.
After driving it home from the shop, when I got out of the car I noticed the cooling fans had engaged. I hadn’t heard that in a while but thought nothing of it, until they started engaging after every trip no matter how short. So far after three days, the car seemed fine, with the exception of the fans coming on constantly.
Then, yesterday afternoon, after a short 8 mile round trip to a store, on the way home, it redlined. Well I freaked and pulled into the suicide lane to avoid traffic. I sat for about 2 minutes and popped the hood. When I opened it, to my surprise, there was no hisssing, no fluids leaking, no evidence of your typical overheating.
I then got back into the car, started it, and the temp started dropping fairly quickly. At this point I don’t remember the fans, but I know I had turned off the AC. After about 5 minutes I was able to drive the car home (about 3 miles) with no issue. Thinking it may have been some “Jaguar” gremlin fluke, I took the car back out. Well the temp started to creep up slightly after about 10 miles, but then I turned off the AC and that straightened it out almost immediately.
Im at a loss. All fluids look good, cars running like a bear, just can’t explain it.
Any thoughts? Many thanks in advance to all.

I had the same problemm where only one coolant fan was activating, so m sure that both coolant fans are activating properly, especially when AC is turned on. Also, I had an engine that would cool at idle but over heat after a short drive.... head gasket was blown.
 
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Old Oct 9, 2023 | 03:24 PM
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I just replaced the thermostat today. It’s looked like the old one was stuck in the “open” position, thus the issue is solved🤞
Many thanks to all fir the input!!
 
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Old Oct 9, 2023 | 05:11 PM
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If it was stuck open, it would likely not reach operating temperature.
 
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Old Oct 9, 2023 | 06:37 PM
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The STUCK OPEN was a big problem with the AJ6/AJ16 six cylinder engines that was discovered in WINTER when the heater was needed!
 
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Old Oct 9, 2023 | 07:43 PM
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Maybe it was stuck closed? Anyway, it fixed it, or at least I think it has. The fans didn’t kick on and it didn’t overheat after driving it back from the shop. The fans were kicking on after even the shortest of trips, I knew something wasn’t right.
 
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