Air lock in cooling system

[KimnKim]

Replaced my water heater today. During the exchange process, about 50% of the coach's coolant is vacated from the system (the water heater is equipped with a heat exchanger) and requires replacing as a last step in the process. Unfortunately, and likely through my inexperience during this step, I seem to have created an air lock within the cooling system. I ran the coach for quite some time after replacing the coach's coolant, initially with the rad cap off. While the coolant within the engine (8V92) and the rad seemed to get warm (eventually) and the engine's heat guage reached a steady 170 degrees, the rest of the system, including the connections to the hot water tank's heat exchanger, don't seem to be getting any circulation or, if there is, it is minmal (the inbound connection to the water tank became very slightly warmer that the outbound). Once I replaced the rad cap, no pressure seemed to build.

Can anyone offer a suggestion to get back on the right track?