Pressure Control for Loaded Trucks A cooling system under load cycles pressure constantly. A standard cap lets coolant escape past a tired seal; this reinforced version holds the set pressure and returns coolant to the circuit instead of losing it to the road. Built heavier than standard Reinforced body aimed at loaded and off-road work. Sealing ring and relief spring sized for constant pressure change. Direct fit to the original expansion tank neck, no adaptor. Black finish,
