Small cracks leaking coolant into the combustion chamber wont necessarily leak into the oil pan. Last summer I experienced a sorta hydro lock one afternoon...lasted about 2 tries and I got curious. Since I have a few spare heads I decided to pull it....I had been experiencing slow coolant loss I might add. I thought the loss was due to a coolant line in the EFI system. Long story short the head ended up being cracked between the seats in #3 and #4 cumbustion chambers. No signs of trouble in oil or coolant. Essentially the engine temperature controlled the leak like a valve. As it heated up mine would open slightly and as it cooled it would reseal. Kinda disappointing considering that head was less than 3 years old...I keep it as a trophy and scavange parts off it now. LOL
~Darin <img src="/forums/images/graemlins/baby.gif" alt="" />