Spray some rust penetrant into the plug tubes and let it soak for a while. Run engine till it is hot bfore attempting to loosen the spark plug. Get a strong plug wrench.
Is the coolant recovery tank depleting as well? If yes, there must be a leak somewhere and a pressure test should should be conclusive. What was the pressure used to test system?
Look out for signs of stains, especially at hose joints and the water pump. Look under the radiator for signs of leakage at the drain plug.
Friday, January 14th, 2011 AT 2:34 PM