How long does it take for water to damage an engine? I recently purchased a car and after 31 days the engine locked and the mechanic is saying it was because of water damage. I have not driven in a flood or high water although I did have my vehicle splashed with a lot of water while driving. He said the air filter is wet and there was water in the oil pan as well as pieces of blown piston. This seems weird to me so please help. My insurance is paying to replace the motor but it just seems unlikely to me. Tell me what you think?