First off Ill say that my vacuum is tight, it holds well, shifts are great, etc. So there is no real issue there.

There was a broken nipple on the line from the pump to booster, Ive changed the line and reverted it all, but this happened before and after.

When operating, I hear a slight humming noise, almost like a muffled kazoo sound, coming from one of the vacuum lines or connections (perhaps yellow lock connector or one of the check valves). When I turn the car off, it "sucks" making this sound until I suppose there is enough air to balance it out and then it goes away.

Even with air leaked in (assuming that is the cause of the sound), there is plenty of vacuum to operate locks, it holds a good long time, etc.

Has anyone seen something like this before? some sort of humming sound coming from the connections up by the oil filter?

A cursory look didnt let me ID it.

thanks!

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

The vacuum control valve on the injection pump is features a "controlled leak" and normally makes a buzzing sound.

This is coming from the mess or lines over the oil filter though. Ive not noticed this on any of my other 616/617 engines, which is my reason for concern.

That is interesting though. Perhaps the controlled leak characteristics on this one is slightly different than the others. Lots can happen over 30 years.

Ill have a listen at that point to see what I find.

Thanks!

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)