01-16 6.6L GM Duramax 185 Degree Front Thermostat with O-ring Fits Duramax Engine Models LB7-LLY-LBZ-LMM-LML Gates #33946 GM# 97241129 – The reverse poppet thermostat opens against the flow of coolant from the water pump. The coolant, under water pump pressure, is used to help the reverse poppet thermostat stay closed when cool to reduce leakage. This type is engineered with a self-cleaning, self-aligning stainless steel valve – The offset thermostat with jiggle pin valves is equipped with a special valve in the flange, which allows trapped air in the system to escape and permits the venting of air from the system when filling it with coolant
