I just replaced the water pump and the fan clutch on my 86 f250 with the 4.9l motor. After I swapped the pump I flushed the system with fresh water, then I drained it and filled the system up with 50/50 coolant, no biggie. But then after I let the motor warm up I noticed it was getting hot again, so I turned on the heater, no heat just cold air. Then just as I was going to turn off the motor I hear a loud boom. The radiator exploded, top and bottom caps actually blew off the radiator. Why? is there maybe a plug in the system somewhere? doesn't make sense. I don't want to get a new radiator if it will explode to. Any ideas? Anyone seen this happen before? This happend to me last winter with my Scout II after I had flushed it, except it blew a heater hose, no big deal.