Glort, hard surface cavitation erosion is caused by the implosion of bubbles (in a liquid) formed on a surface under localised vacuum conditions, this causes the displaced liquid to impact the surface at high energy, this can damage a boats screw or a water turbine runner, also commonly occurs on the water side of diesel engines fitted with thin, wet cylinder liners, due to firing event resonance. Ultrasonic cleaners use this effect I believe. Research has shown that very high temps are momentarily achieved during the collapse of these bubbles.
Dieselgman, another possible cause, an engines fuel combustion produces copious amounts of water vapour, at normal temps this is invisible and has little effect, at low temps this may condense and combine with combustion or incomplete combustion by-products to form acid, this acid may attack a cast iron matrix and if it gets into the lube oil it may also attack the bearings, the original CS engines are prime candidates for having had extended cool running periods.
Mark.
