over heating problem please help

Hello I am new to this forum and was hoping to get some info on my 92 dakota. My radiator blew a hole on the top front side at the seam Tuesday. Then before I could pull over my oil cap blew off. I let it set for 5 minutes added water back to radiator then started to drive closer to home. I made it fine and the wierd thing the truck never over heated the rest of the way temp stayed the same also it was a 20 minute drive.Was wondering if anyone could tell me what caused the radiator and cap to blow.Also will it happen again when i put in a new radiator and cap. I checked thermostat and it works fine but will replace just in case. Please help and thanks very much Piratehand

Could there have been something covering the radiator? A piece of garbage or paper come up off the road and prevent air from getting to the radiator? Is your fan working properly? Fan clutch could be going. Just some ideas, hope this helps!