Type of sound it makes gives a clue. High pitched like a tick tick sound is usually valve train, while a deeper knock sound is a rod bearing. Valve and rod knock are also different speeds. At idle the rod it knock knock knock, while a valve will be ticktickticktick. Valve ticks can also fade when slowing from high RPM. Anything that sounds like metal to metal while in park is usually internal and expensive. I have had a case of a bent flywheel that was taping against the back of the crankcase, but those are very rare and usually on engines that have an open area behind the pan where something can be kicked up into it.
Location of the sound is also critical in diagnosing. Front, back, on a side, etc. I have had water pumps fail so the pulley was tapping the timing case, and it to would increase/decrease with throttle. Since you mentioned fluid spray, I would look there first.