Need help with my hose

The only difference between what used to be called "overflow" and a true "coolant recovery" is that if the hose is down near the bottom of the "recovery" can it will attempt to act as a return. "This is good." Why would you not

It occurs to me that if the can is TOO FAR DOWN in the engine bay, this might be the cause, as the low mount can might not return fluid, but rather causing a vacuum. The can needs to be towards the top of the engine bay