Volvo Repair: Volvo S60 Y2000 Water Coolant Loss, head gasket failure, coolant loss

Question
Recently my S60 started to loose water coolant and goes from max to min within 2 days. Each day I drive around 60-80km. Have pressure tested the system, checked all hoses and clips, checkes oil colour in case of head gasket failure, checked water pump gasket, checked radiator for leaks, but to no avil. It does not look like there is a leak but possibly water evaporating but I cannot find the source. Any suggestions?

Answer
  David, if it's not leaking externally, it has to be burning it which would be headgasket allowing cooant into the combustion chamber. Presswure test the system again, cold, pull the plugs, have an assistant turn it over and watch for moisture (spray) coming out of the holes.
   The only other posibility would be if it's getting into the transmission cooler? Check trans. fluid condition and level. If it's milky and overfull, correct immediately and do NOT drive it!

Mark