3psi one way check valves

Running an open system without pressure and losing coolant? Well slip this in the overflow tube and voilà; you have mild pressure to keep the fluid in your system.  In an non pressure system the fluid evacuates due to: excess coolant thermal expansion  excessive flow from higher speeds  blocked and clogged tubes  water pump impeller design flaws This handy dandy little check valve will not suck back but it is a great tool for keeping the fluid in for longer.