Quote Originally Posted by Leon R View Post
I guess it depends on how long you drove it with water in the crank case. I have seen people getting away with it, as long as they caught it quickly.
If it were just water, you are absolutely correct as water does not have the same effect as antifreeze when mixed with oil. When mixed with oil, water will cause sludge to form degrading the lubrication properties of the oil but in the short-term, not catastrophically. The problem with antifreeze (ethylene glycol) is that when it mixes with oil, it increases the viscosity and glycolic acid is formed, the resulting imulsion becomes abrasive and corrosive attacking the softer bearing surfaces first (the cam bearings) along with the mains and the rod bearings, the cylinder walls will also become scuffed. This damage occurs very quickly once the oil has been contaminated. From what Starglider had posted, the contamination was not discovered until the crankcase was so full that the reduced case volume caused hydraulic-lock and blew the main seals when he attempted to restart it.