Things to do to be prepared. Go to the help isle at any auto parts store and get an extra or even two extra inlet or outlet couplers that go to your heater core. I have a 2001 2500HD 6.0 and my radiator was leaking right where one of the hoses go into it. It is usually a very small and slow leak until it starts to crack more. Must of the time it will be the inlet couplers. I would definitely check your water pump. I have replaced mine once before. It cracks then leaks from it's seals. It will drive for awhile but replacement asap if you can.