beside the thermostat, what other part could cause the radiatoe to overheat

radiator fan. bad temperture sensor. air an the cooling sistem. bad wather pump. obstruction in heater core or radiator. leaky cooling sistem.

Could be any of the previously mentioned items. Could also be a blown head gasket. Usually the coolant turn orange rust in color. The most accurate way to test for a blown head gasket on a gasoline engine is to test for the presence of carbon monoxide in the cooling system. Snap-On, Matco (part # CO 2000), and Napa sell a tool to check to carry out this test. Another link to a supplier of this tool is http://www.etoolcart.com/combustion-leak-detector-lis75500.aspx. Carbon Monoxide is only present if there is a blown head gasket or cracked cylinder head. http://www.arrowheadradiator.com/head_gasket_or_combustion_leak_test.htm I think the napa part number 700-1006. http://www.blockchek.com/instructions.htm . Signs of a blown head gasket are coolant loss (frequently have to top up the coolant level of the engine without seeing an obvious leak), experiencing over heating or rough engine running or the presence of white sweet smelling steam from the exhaust. A badly blown head gasket may allow engine coolant and oil to mix.

Could be a partial obstruction in the radiator. loss of water may be coming out of the overflow as the water pump is pumping more water than can flow through the radiator and backs up through the overflow. I had this problem last year and replaced the radiator with an aftermarket radiator which I purchased for $180.00. I had to call around to find the best deal. Some quoted me $360.00 for the same radiator and a genuine Toyota radiator was sky high. It installs easily. Tom