Cooling water leak

Car is a Jaguar XKR 1998 supercharged. Loseing around 1lt of cooling water per 10 miles, thermostat, water p/p housing shows no visable leak, no white residue on dip stick or oil filler cap, no visable leaks before stripping out super charger to check both hoses in v8 valley, both hoses appear to be in good condition as far as I can tell all other hoses are in good condition, engine oil level has not risen.