I actually have a 2006 C5500 that we have put 4 Factory radiators in. After a year or so, when it sits more that a month or two, the radiator starts seeping out of the drivers side at the bottom. Sometimes just a little drip but mostly moist.
The current radiator is 6 months old and less than a thousand miles on it. When it sat and then the temperature in Georgia got colder it seeped than stopped. Havent' noticed it in the past month or so.