300d sounds like a pipe organ!!!
 

I have a feeling that I'm about to describe a symptom that has already been covered here before, but I can't seem to find the right search word to get a hit in the archives.

I just returned from about 20 miles on the freeway at 65-75 mph. Right after shutting the car down I heard a high pitched whistle that gradually increased in pitch until finally fading out. While still hearing the sound, I pushed down the drivers side lock, thinking that it might be vacuum related but no change in the sound. I started it back up and then shut it down again and didn't hear the whistle again. Didn't sound like the antenna motor(?), don't remember if the climate control was on at the time (but was running most of the trip home). HMMMMMM

1979 300D

Where was the sound coming from (engine bay, cabin, trunk?)?

Ah yes, a critical piece of info. I think it was coming from the engine compartment or maybe under the dash...... It was hard to tell, actually but I don't think it was coming from the trunk area. That doesn't help much does it?

Have you been having to add coolant to the radiator? Might be a leak in the cooling system and the pressure bleeds off after you shut it down....
I guess it could be something related to the Evil Servo and related systems, both vac and coolant.

Haven't noticed any coolant leaks. I did re-install the fan yesterday (was in the trunk when I bought it).

I have yet to meet Evil Servo. Should I look forward to it?

How long did you run it after the restart? It could be the brake booster leaking vacuum by at the master cyl grommet or check valve grommet, & maybe it didnt run long enough to replenish the booster vacuum (large area to evacuate) the check valve would isolate it from the rest of the system so locking a door wouldn't make a difference. Have the brakes felt a little weaker or harder than usual?

Ran it again for a minute or less, maybe will run around the block a couple of times after the little one goes to bed and try again.

Have not noticed brakes working any differently.

Look at your fan clutch next time and see if it continues spinning when the engine stops. Since you just reinstalled the fan, my money's on it.

Call the last owner and asked if there was any reason he pulled the fan. What I was wondering is if the fan clutch had no or little oil did the freewheeling fan somehow make a weird noise. Inertia would keep it going for a time and the clutch unit might have been hot from the freeway drive if excess slippage was present. Noise like a pipe organ is a little strange though. Any identifyable tune?:D

I believe that the PO would have told me if the fan clutch was misbehaving. I think he left it off after changing the belts thinking that it would help keep the car up to operating temperature this winter.

The way I understand the fan clutch works is that when the fluid (or semi fluid) inside gets hot (or warm), it expands enough to NOT allow the fan to freewheel. If the cluth was shot, then I should hear it freewheeling after every shut down. Is my logic correct?

I will try to get the car up to temperature and see if I get a repeat performance today.

No recognizable tune, very spooky though.

my 79 does that after a decent drive, it stopps when I step on the brakes, so it's vacuum related on mine. try to step on the brakes next time you hear the sound to see if the booster makes it stop.

Will do.