95 XJS Overheating

I have 95 Jaguar XJS, 4.0 six cylinder with 118,000 miles. It stated to overheat so I pulled over. A little steam did appear from under the hold. I don't think I had a major boil over for I stopped driving before the temperature gauge reached the red zone. I allowed the car to cool and made it home since I was less than a mile away. The engine runs fine as if nothing has happen but the car will not hold coolant, it just runs to the ground. I am unable to lift the car to inspect. What would cause the overheating and what has occurred such that the car will not hold coolant.