Over the weekend, the engine in Mondial overheated after running it for about an hour and a half. I was seeing very little water flow out of the exhaust pipe. I changed the impeller and even tried drawing cooling water from a bucket. My guess is that the the water orifice into the mixing elbow has plugged. From reviewing the archives, it's apparent that others have had the same problem. How have you gone about fixing it? Can the mixing elbow be roto-rootered out?