Squeal or whistle is a leak on the pressure (intake) side, occasionally exhaust.

Check for leaks first.

The turbo wheel will not spin, it stops almost instantly if you push it around on most diesel turbos. Gas turbos spin a bit more freely, but none really "freewheel" very long because of the oil seals. However, you should be able to turn it with a fingertip. A barely perceptible amount of side play is OK, axial (in and out) play means bad bearings. So do any "tight" spots in rotation. If you have to push much, the bearings are shot.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!