I have a 95 XJS 6 cyl. A while ago I filled the coolant tank to the top. Yesterday I looked at the level and It is down about an inch. Is this a sign that I may need a head gasket? There is no leakage of coolant that I can see.

 

Look for one of these 2 teltale signs. Milky colored oil and steam like emmisions from the tail pipe when hot that smells sweet. If you dont have either continue looking for other explanations.

A coolant pressure tester can be employed. It attaches in place of the radiator cap then you pump up the system to 15 to 18lbs of pressure and see where the fluid goes. When not moving and cold a drip can become more visiable.

Might be as simple as a bad radiator cap seal that allows fluid to expel when hot. Small pinholes in a radiator or a leaky side tank is often hard to spot on an xjs.

 

It'll expand and burp coolant sometimes if the caps are weak or air will evacuate and it'll drop. When changing out my many coolant hoses, 3 of which have burst in the past month, every time I'll do the procedure to the letter and still have to add another couple liters it seems. After a few warm-up/cool-off cycles the coolant amount stays the same. Probably just air leaving thus dropping the level abit.

 

The level of 1 inch down is normal. Just monitor it and check every week or so and see if the level goes way down. Also, look for leaks on the ground under it, etc...