Radiator overflow tank

[sdleaton]

My son has a 96 Avalon. he has replaced radiator, thermostat and new overflow tank. The car does not show to be running hot, but, the water will get hot and pop off the overflow lid and spew boiling water causing smoke from hitting the engine and water to spew onto windshield. He has had it on a small diagnostic machine and it shows nothing going on. The overflow tank stays full and doesn't let the water back in the radiator. Hoses are good, squeezing them you can see the coolant moving back and forth. He was going to try the water pump but that was a lost cause as the crankshaft pulley is sitting in front of it and the bolt is pretty much welded on and won't come off. Even after all the different ways of getting it off. He has no money to take it to the shop so is working on it on his own. Any ideas of what he can do?
He's thinking maybe the overflow is too low, but, it won't go any higher and still be able to close the hood.

[denverdog]

i'd check the coolant temp sensor. soemthing is geting way too hot, even if it doesn't register on the guage.

[TedL]

Search for threads on changing timing belt. They give procedure for removing crank bolt. But before changing water pump, I'd make sure it's bad, which is not likely.

Unless overflow hose is clogged, or crushed closed when hood is closed, it's the "radiator" cap, not located on the radiator, that controls flow of coolant between the overflow and sealed system. Not the overflow tank. Make sure hose entrs bottom of tank or the extension tube is in place from cap of overflow tank.