LMM Coolant Tube OEM Cut And Weld 2007.5-2010 GM 6.6L Duramax PPE DieselPPEs modified coolant tube for LMM Duramax 6. 6L is designed for use with PPE Up pipes and Manifolds. Our experts cut, reposition and weld the coolant tube for proper clearance. The coolant that flows through the tube provides heat to the heater core for the in cab AC Heat system. Features: Modified Coolant Tube For use with PPE up pipes and manifolds Works with the AC Heat styem Sold Individually Applications: 2007. 5 2010 GM 6. 6L Duramax Engines