if the head gasket is gone then do as above, signs are losing water but it aint leaking, mayo around the oil filler cap, sometimes mayo round the water filler cap. and in extreme cases. water pissing out of the exhaust or if ya take the oil dip stick out an its like mayo.. also lots of pressure in the coolant tank. but for the love of god don't take the coolant filler cap off when its hot, me the silly person did it when i was 17 and ended up in hospital with burns to my arms and hands.