If i just let the car sit while its on and leave it in park the jag will get VERY HOT to the point it'll overheat. It doesn't take long either, around 15 minutes.

 

Check to see if your fans are running.

 

Cunningham, I think you are going to find that the controller for your fans is shot. Common thing to fail on our cars. The check is easy. Start up your car and turn the A/C system on full blast (as cold as you can set it and make the fan run as fast as it can). This will force the fans to run. Now, pop the hood and see if your radiator fans are running. They should be running to the point that it feels like you are standing out in a corn field on a breezy day (ie, pushing your hair around on your head). If you are not getting this, then odds are your fan controller is dead. You will want to check the fuse for the fans just to make sure that you didn't accidentally blow that, but 99% of the time, this sort of issue is the fan controller.

Now, as a side note, if you get a recycled controller, make sure that you get something IN WRITING!!!!! that says that if it doesn't work, you can return it for either a new item or your money back. Because this is a common problem, there are a lot of them out there that are failed that people try to sell.

Please note that in later 2004, Jaguar realized that this component was failing too often and revised the controller. So, you will find that there are 02-03 controllers and 04+ controllers. You can install the 04+ controllers, you just have to buy a pigtail to convert the plug of your 03 to what the 04+ controller will accept. Your local dealership can get you the pigtail.