So I can't seem to track down any leaks that might be whistling. And this noise is starting to bug me. Trying not to turn on the radio to drown this sound out...

One more question. Is it possible that this sound is actually the bearing (I'm assuming there is one) in the turbo fan going south? This 'screech' is not there all the time, only when I am either accelerating, or at higher highway speeds (65+). Does the turbo fan run constantly at speed? If I cruise along at around 55-60, I can get it to stop, but if I just tap the accel a hair it is there.
Also, If I remove my foot from the accel, it stops immediately... Any thoughts?

I was wondering if there was some way to test turbo fan bearing? Thanks

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1981 300TD
1985 300TD