1796 Chevy GMC Hummer 2006-16 6.6L Duramax 6.6L Turbo Diesel hi flow water pumpNo platstic impellers and no imbalanced thick walled cast impellers. on this 6. 6L Duramax diesel water pump. We designed an impeller with a larger eye, an increased vane count and a reduced impeller vane clearance to increase flow and prevent overheating for big vehicle that are under a load. It achieves greater flow rates, higher head pressure and a more efficient flow. The impeller color is due to Type II Class II military grade surface coating