What would make my radiator do this?

What does the radiator do?

I may have already replied to this, but it looks like too much pressure is getting into the cooling system. Two things could cause it. A bad head gasket could allow compressed air into the system. However, the radiator cap should release pressure at around 15psi. If the radiator cap isn't releasing, it can cause too much pressure to build. What to do is this. With the engine cold, remove the radiator cap and start the engine. Does the coolant spray out of the radiator? If not, the head gaskets should be fine. The next step is to try replacing the radiator cap with a new one. If I recall, the original ones were set to release at 15 psi. You may want to try a lower release. I believe the go all the way down to 9 psi.

Let me know if you have other questions.

Joe