I just got my 98 xj 8 Jag, and It leaks from the plastick retention tank underneight the front driver headlight assymbly. I just crawled under the car and saw the plastick tank and I see a tube comming out of it. Which looks like a hose should be connected to it. And their isn't. The tube is just there. I don't know if it's missing a hose. I can't really see if the tube has a hole going into the tank or not. CAN SOMEONE HELP ME AND LET ME KNOW IF SOMETHING IS MISSING?

 

If this is the "coolant reservoir" you're describing then it's possible that the "tube" that has no hose connected to it is the overflow outlet (it doesn't really need a tube, obviously it's better if it's there. It's function is to let excess coolant out in case there is an overfill)

In any case -- how do you know the car is overheating. Are the gauges showing high readings? Please describe all the symptoms (also known as subjective evidence).