Have you pulled the oil dipstick to see what the oil looks like? Hope it doesn't look like a choc. milkshake. The question is has any antifreeze made it into the oil, and if so, how badly (if any) has it damaged the bearings and whatnot.
These are highly engineered precision vehicles, the first step in diagnosing the problem is to strike the suspected offending part sharply and repeatedly with a blunt object, then re-test.