I have a 2011 3500 has just 21000 miles I just bought the truck. I had all new coolant line put in along with other things. It has blown 2 brand new coolant lines right off the fitting. The shop I brought it has pressure test it everything came back perfect no white smoke. The shop believes I have a cracked head causing pressure to blow the lines. I find that hard to believe. Any feedback would be great.