Yea, sounds like a blockage somewhere, or possibly corosion in the water pump reducing the efectivness. You'll probabnly thave to do most of what mrshin mentioned before you even find the problem. best to give it an over hual while your at it.
When refilling the cooling system, use the red toyota genuine coolant. its the best stuff for toyota engines, and better than most other stuff on the market too boot!