you never know sometimes theres weak spots in the metal. im not saying your wrong first things first got to see if anything is flowing and the easiest way to do that is watch the radiator with the cap off. if not check the thermostat if not that then it would be the water pump. if not that then the radiator itself could also be blocked if the car is over heating. i had that problem at about 100,000 miles and put in a new radiator and bam it was back to normal.