aliusv2
Favorite Answer
Unless you are talking about the HVAC reservoir you don't have one. If you are talking about the HVAC reservoir then it's inside the dash. Vacuum source for the 5.4l is the intake manifold. Look around close to the throttle body you'll find everything you need to know. Now, there are check valves. And they can be tested either with a special tool or by disconnecting them and sucking on the outlet like a straw and seeing if it leaks.