During a routine oil change and general maintenance pre-flight walk-around to the mighty Cummins yesterday, I found both exhaust manifold bolts on #6 loose, very loose... I wonder what kind of damage I can expect to find to the Manifold gasket. Are these things very durable or are they fragile. Are they stamped sheet metal or do they have asbestos like material sandwiched in between. I think I caught it before it was loose for too long, but who knows... .