When I bought my '06 RTV900 and discovered the cooling system was not intact. I fixed it and thought everything was good until I saw fluid coming out the waterpump weep hole, I bought a new waterpump and when removing the old pump discovered there were NO fins left on the impeller, just a glob of potmetal on the shaft. It could not have been moving much if any coolant thru the engine. I never had any problems with an airlock in the engine. Everything is fine now.
Bryce
Bryce