Mercedes-Benz: 300SD Turbo wastegate sounds like coach-whistle at speed!

300SD Turbo wastegate sounds like coach-whistle at speed!
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mine <82SD> had a problem with the gate not closing and taking forever
to get to speed.plus having a mind of its own!

cleaned out the bango fitting on the intake and replaced the vacumme
line leading to the altitude compensator
no more lost power.

the choo choo noise MAY be the gate not properly been told what to do.
mine makes noise at aprox 1/2 speed

case
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(Doug)
I'm going crazy! My turbo is silent until I hit 60mph, whereupon it
suddenly begins making a shrill coach-whistle sound. If I accelerate it
vanishes, if I go slower it vanishes. If I cruise from 60mph and faster
steadily it's there screeching away under my hood, amazingly loud. I
think it's the wastegate as it's not a bearing noise. What would make a
wastegate sound like a coach-whistle? How do I replace it? I looked at a
removed turbo at a shop, the gate seems to be impossible to remove, four
screws on the back remove a cover and gasket revelaing a slot sized for
a huge flathead screwdriver. If I turn the slot it rotates the top half
of the gate. I also noticed the gasket that I removed from the back
plate was split inside. Could this be why my wastegate is whistling?
If it helps, it's a 81 300SD. Please feel free to reply to my personal
email: com. Please remove the obvious
spam-foilers. I'll check the group too. Thanks!
Doug

the case, minus a few cans!