[scaggsj]

Id check the water pump cause the impeller in side could be ate up and therefore not able to pump. I had this happen on a 98 dodge not a common problem but if the coolents never been changed and become acidic it could happen. Mainly cause you said theres no pressure in the upper hose another thing could be a bad thermostat I know you said it was changed but Ive had alot of brand new thermostats be bad from the get go. The pressure test is a good idea too.