What kind of oil was used? If it isn't heat, its conductivity. As Steamtyme said - most of the setups have the fans removed and bypass chips are used on the fan pin jacks. You'd need a way to circulate the oil or use a bubbler in the way myself and others have designed.

If you had an immediate failure, find out what happened because it sounds like something seriously shorted out and if your oil is non-conductive as it should be, this short is likely to have been caused by something else.