Check your fan. If the viscous coupling is shot, the fan will spin freely and erratically about after you shut off the engine, and could be causeing that clanking sound.
That is what my car did.
If it's the fan, the gas smell is an unrelated phenomena.
A gas smell can be a leaking injector. This could be dangerous, as the leaking gas or fumes could ignite. Not good.
Always put a quick-disconnect on the + side of the battery terminal, and you could prevent a disasterous fire.
Semibodacious Transmogrifications a Specialty
1990 300D 2.5 Turbo sedan 171K (Rudolf)
1985 300D Turbo TD Wagon 219K (Remuda)
"Time flies like and arrow, yet fruit flies like a banana"