Seems like everybody was on track. I took out the thermostat and drilled a small relief hole as Scott suggested. It worked great. The engine had been sitting for about 3 years (which I neglected to mention), so maybe that contributed to the air pocket issue. In any case it works great now, I thank all of you for your responses. This was really getting on my nerves (and the antifreeze was getting on the floor). Thanks again, much appreciated.
Don
