Leaking Coolant from Jaguar XJ8 on 1999 Jaguar XJ8

I have a 1999 Jaguar xj8. it runs perfectly with no loss of power or indication of engine problems. However every few weeks I am having to top up the coolant with coolant low indications. I cannot see a leak, could this be indicative of a bigger problem? I am worried to take it somewhere to be told (wrongly) that it is a bigger problem than it is. Conversely is it likely to be the sign of a bigger problem. She does seem to smoke a lot, although weather is cold these days. Sometimes when I leave the car I smell something that I can best describe a sulphurous. Is it all going pear shaped?

1 answer 2 comments
pressure test cooling system for leaks if none found then remove spark plugs with the pressure still on the system and crank engine over to see if anything blows out the cyl if so then you probably have a blown head gskt
thank you. I suspect blown head gasket. that is going to cost me a fortune isn't it?
the average cost is approx 600 to 800 but i dont work on jags but I would assume that it would probably double that