I just took down my oil pan to correct leaks at both the rear and front (neoprene) seal. While removing the pan, I discovered that the rear of the pan was imbedded into the cork rear seal. The groove created is lined with black silicone - see pictures. In fact it looks like someone even sharpened the edge of the flange so it would bite in easily. Is this the correct way to install the rear of the pan?