Toyota Repair: 85 4Runner Coolant Problems, blown head gasket, radiator hoses

Question
When I add coolant to radiator it boils and blows back out as the engine gets warm (doesn't happen when engine is cooler).  Radiator and engine have been checked and there is no blockage.  Also, upper/lower radiator hoses replaced, as was the thermostat.  Could this be a bad water pump?  I didn't get the usual signs of water pump failure (water leaking from housing).  The engine overheated the other night, so there is a possibility that I have a blown head gasket or bad heads, but I feel like this problem may be independent of that.  Thanks for any help.

Mike

Answer
It's a cooling system circulation problem, if the radiator and thermostat are good there may be a problem with the water pump, you can have a toyota dealer or any repair shop do a block test to see if there is an internal combustion leak this will tell you if the headgasket is leaking.