Hi all!

For the most part I lurk and keep to myself but after a couple of hours searching I realized I need help. Sorry for the following wall of text but bear with me.

For starters I have an 03 XJ8 with approximately 78K on it.

Last weekend I drove my car and noticed as I sat idling that a new noise appeared. Never before had the fan turned on but there it was spinning pretty loudly. It wasn't hot at all, Oregon weather at this time of the year is mid 60's if that. Anyways, I drive to my families home an notice that the fan doesn't shut off after I have turned the engine off. A few minutes later it quiets down and turns off. The in dash temperature gauge hadn't flinched and stayed smack dab in the middle. So that night I drove back home, approx 60 miles and the fan continued on, the dash didn't indicate anything and put her away in the car port.

I live close enough to work that I can walk there and back so I haven't had the opportunity to drive it or look at it until this weekend. This is were things get worse... I drove it again to my families out of necessity and the fan triggered again. I drove it maybe once in town for 15 mins and didn't drive it again until today to drive back to my home. On the way home everything seemed alright and told myself 'alright no more driving it until I square things off' and as I said that I notice the temperature gauge rise slightly above the halfway marker. To avoid it going any higher I pulled over almost immediately and shut the car off. I waited about 20 mins, turned the engine and the heat indicator was at the halfway mark. I drove it literally 3 miles towards my exit the indicator began to creep/dance its way almost to the 3/4 way mark. I say dance because it would slightly rise and lower and then rise until it go to the 3/4 mark. The needle wasn't jerking or sudden but subtle. So once again I pull over again wait about 20 mins drive again and repeat this one more time until I got home. I would have to say that the needle did move more on the slight tiny inclines of the road but they aren't anything big.

At any rate, I know that there is something happening that I need to replace but with the gauge actually moving it introduced a bit of fear in my mind. The needle never touched the red section but it still worries me, hopefully I didn't damage anything? If there is anyone that would be so kind as to point me in the right direction I'd greatly appreciate it!

Once again thanks to everyone for putting up with my novel write up.

 

You do not mention a low coolant message so the next up is a thermostat and/or water pump. Both are easy and since you are going to have to drain the coolant I would suggest a complete rebuild of the 12 year old system. Thermostat, pump, upper and lower radiator hoses, plastic cross over pipe, the short connector hose and the serpentine belt.

I can never keep it straight but if the '03 XJ8 still had the 4.0L engine replacing the plastic thermostat tower with the aluminum unit is highly recommended.

 

Despite a temperature gauge that is the equivalent of an idiot light, it is
pretty clear that there is a problem with the cooling system.

It isn't going to go away no matter how much you pray. The Jaguar
V8 is not tolerant of overheating.

There is some good advice in the preceding post, and many threads
on the cooling system for further reading.