Well it seems as if the air trapped in there was a good thing, woulda sukked bad to have that happen tooling down the road.

 

Today I filled my box up a little past full (it was empty) and turned it lock to lock pretty slow about 10 times with the front tires in the air and engine off, then toped it back off to the full mark and started the truck and works perfectly. Don't know if it would help you but it worked for me.