black sealant used on Saturn's

Hello, I have been struggling with a trunk leak for weeks now. I
finally found out what the problem was. The black sealant they used to
seal the different panels under the outer plastic fenders has gone bad.
This is a 97 SC2. At first I thought it was the rear window
seal.....but after re-sealing that with silicone the leak continued. I
was able to pull the rear quarter panel away enough to see under it.
The black sealant used to seal the seams on the under body looked ok
but on further inspection it was hard as a rock. With a screwdriver and
a hammer I barely hit it and it broke away. The seam underneath it was
rusted. There it was, the leak into the trunk. I sealed that with a
generous coat of silicone sealant and the leak is gone.
Dan.