Radiator Pressure Adapter - GM/GMC Designed for the L5P Diesel Engine with two tank caps. One cap is located on the side of the tank (Vented) with right-hand threads. The other is located on the top of the tank (Non-Vented) with left-hand threads. This is designed to eliminate any chance of installing the non-vented cap where a vented cap is required. O-rings on the center core seal off the tank vent port for proper testing. Applications:. 2017+ Chevroet Silverado. 2017+ GMC Sierra w/ Duramax 7122