Air in heater housing?

I have a 1992 Hot Springs Sovereign which we drained and refilled on 11/9/12. The jets are working fine and the circ pump is working as well, but it is not heating. When I initially discovered this on the night of 11/9, the heater hi limit switch was tripped. I pushed the red button in and the circ pump kicked on immediately. The next morning after about 12+ hours of being on, it was still only mildly warm. The strange thing is that I can hear water sloshing in the heater housing like it is not completely full. What is the best way of going about releasing this trapped air? I've cycled the jets on and off repeatedly. I've left the jets running for 5-10 minutes at a time, and I've cycled the circ pump on and off numerous times to try to "burp" the air out. But nothing has worked so far. I even drained the tub again to past all the jet levels and refilled through the filter holes.

Every time I drain mine I need to bleed the air at the filter AND crack open the uppermost fitting on the heater while running on slow speed to bleed off all air in the heater, hope this was helpful.