Those rubber gaskets go through a lot of heatup/cooloff cycles, and they will eventually degrade. I had to change out a shot to $hit one on my '05. It's not the good old days, all rubber is some synthetic facsimile of real rubber. Look at how badly our tires get after 5-6 years, even with very low mileage. It's almost like they rot from exposure to air. In fact, what else could it be?
