1980 300TD Non-Turbo "Loping or Wa...Wa...Wa) engine sound

[1980240d]

Hi All,

I am looking to buy a 1980 300TD that has an unusual noise at idle and through the RPM range. I would call it a "loping sound" (like a WA WA WA, or WU WU WU sound) but the engine is not loping - it actually idles very nice smooth. The sound is coming from the area of the air cleaner and or intake. It is not the air cleaner mounts. I did not notice the noise at cold start-up, but during and after a test drive.

The engine starts and idles fine when cold.

The passenger side motor mount is shot due to a leaky SLS pressure hose. I did not see any gross movement.

I really wish I could have taped the noise to post. Oh well.

Any ideas based on this limited description.

Thank you!