1994 Toyota Previa

Engine Cooling problem
1994 Toyota Previa 4 cyl Two Wheel Drive Automatic 190, 00 miles

My 94 Previa is overheating. I changed the thermostat but problem still exists. I don't see any liquid coming out of weep hole in water pump. I am pretty sure temp guage is operating correctly. Once engine heats up temp rises and fluid returning to resevior is way hot and vents out through overflow tube. I was told there may be air in the system following the thermostat change. Is that possible or do I need to be looking elsewhere?
December 15, 2009.

Check those hoses on the overflow bottle for blockage if okay bleed the system

Dec 15, 2009.