I had my car in the shop to replace the heater core and the mechanic noticed I where I was leaking oil. It was coming from the casing for the timing chain. The leak was in between that casing and the block. He said when he called nissan, they said they have never heard of that gasket every breaking. Can anyone help me with directions or opinions on fixing it. He thought you could open up the casing and take it off and then seal it with silicone. The only thing is it is a little hard to get to. Any ideas?