This is very common for this model truck. Mine did the same thing. And I took it to get re sealed and the people said it is very common for this model/ year of trucks to have that problem. They fixed it and it hasn't leaked since.

 

It has to do with the original sealant the factory used. If you get it re-done, especially professionally, there shouldn't be anymore issues as the new sealant is supposed to work better. Mine has a warranty.

 

I had to fix mine a few months back... did it myself and it was a pain in the **** but its fixed. Getting the old sealer off was the only hard part. But i sure am glad i fixed it.