My '88 760 turbo recently developed the following symptoms:
1.An intermittent high pitch squeal when accelerating. This has been present for approximately 3 weeks. The sounds seems to be coming from the engine.
2.In the last couple of days, a distinct lack of power
3.When attempting to accelerate, the turbo gauge climbs to the mid-point and the engine seems to bog down and won’t perform until I let off the gas, at which point the turbo gauge goes to the left. If I accelerate slowly with the gauge on the left, then there seems to be enough power to get up to speed.
4.No irregular smoke but I believe the turbo to be original with 285k kms.

Could the squeal be from the turbine making contact with the housing?