A brief video showing what exactly happens when crankcase oil is contaminated by water. This can be caused by a variety of reasons, such as O-ring failure or damage followed by damage to the main seal on the shaft.

Crankcase oil contamination, and oil contamination in general, can seriously damage a pump. With the pump displayed in the video, contaminated oil has damaged a variety of parts, and the pump requires a number of new parts. Much like the pump in the video has developed calcium deposits on the manifold, these deposits can form anywhere in the pump, blocking important functions.

As stated in the video, it is recommended you check your oil before each use of the pump. This process won't prevent the leakage, but rather prevent contaminated oil from damaging the pump any more than necessary. The damage caused by extended contamination may not be immediately apparent, but damage caused will show up gradually, and may be expensive.