I purchased my 03 xj8 about 6 months ago and since the weather has turned cooler here in Tennessee I'm noticing that my temperature gauge is higher than it should be and sometimes smelling hot. There are no leaks I can find. Is it possible that it could be something as simple as the thermostat?

 

I had a similar problem with an 05 XJ8L, but the temp gauge would spike all the way. It was the thermostat. If you replace the thermostat, be sure to burp the system of all the air as you refill with coolant.