This can happen on all engines but is more common on diesels due to engine vibration. Over time, the gasket will shrink and the nuts will loosen slightly. This will result first in small exhaust leaks (evidenced by black soot around the gasket) and the sound of an exhaust leak. If left unchecked the manifolds may begin to rattle and make noise. If caught early enough you usually do not need to replace the gasket.
Problem & Solution
Common among these chassis:
On 615, 616, and 617 diesels from 1965 to 1985 get a 17 mm 6 sided socket on a long extension and re-tighten the nuts evenly. If the nuts are loose on the threads I recommend purchasing new locking nuts available on the website.
WARNING: Loose nuts can permanently damage the manifold gasket and possibly lead to cracked or broken exhaust manifolds!
