He may be superbly loose, but what kind of hands will this guy cold-call a 4xBB raise in early position with? Unless this guy is a total donk, the only hand we're beating here is KQs/AKs. I suspect that he's slowplaying something big after his calls of your big flop and turn bets.

I wouldn't be surprised to see a set or some wierd 2 pair here.