[mdmull]

The coolant recovery system should serve two purposes. Initially, it will help to remove any air from the system, if there is sufficient coolant in the tank after the engine is hot and the correct cap is installed (one that will open upon cooling to "suck" the coolant from the tank. If during this process, the tank empties, air will be sucked back into the system. Without adding coolant to the recovery tank, it may never bleed all the air out.
Secondly, it serves as a receptacle for the hot fluid that expands as heated. A one quart tank should be enough to accept the expansion volume. I have a diesel truck with more than six gallons of coolant and the expansion is not much, if any more than one quart. I believe that you must have excess air in the system, or some leak that allows air into the pressurized system (Hope not). One thing to try is one of the auto parts store recovery tanks $10 or so that has a fill cap. Bring the engine to temp & as it cools down keep some coolant in the tank for several cycles, should "bleed" the air out once & for all.

If, of course, the radiator isn't sufficient, a gallon tank will not be enough.