Hi folks, I have a water leak in my RTV 900. Seat coover stripped and noticed it was coming from water pump area. Removed water pump and noticed it was leaking from a hole in the casing. It was dirty when I took it off so thought it had cracked or corroded but as I cleaned the pump I noticed the hole was engineered....is it missing a frost plug or is it a tell tale that the bearing has gone? Seems strange having a hole from production? Photos attached, any advice would be appreciated. Is there anything else you recommend servicing or replacing while water pump and radiator is out? Many thanks, Dave