My wife called me at work around 4 today. She said she was driving home and saw steam coming out from the front of the car. She was about two miles from home and decided to bring it home because it wasn't overheated -yet.

When I got home I saw that the expansion nipple on the top of the radiator had blown out. There was coolant everywhere. The nipple was not broken so I reinserted it. I tugged on it and it seemed solidly connected. I refilled with MB coolant. It took over a gallon. I started the car, opened the heater and took it for a ride.

It seems to be okay. No overheating, the heater works fine. No leaks that I can see. (It took a while for the coolant to burn off).

So what's the deal? Should I expect this to happen again? Do I just need a new nipple? Is the radiator bad? Is Zeus mad?