I am getting a real gut-wrenching whining sound coming from under the hood of my '86 300SDL. It seems to be when to turbo gets to full boost. What's the possibility that that sound is the overboost releasing pressure?

I am going to try and rig up the boost gauge from my '85 tomorrow and see what it says.

I rebuilt the turbo about 6 weeks ago (the sound started yesterday), but never messed with the wastegate, because it couldn't really be opened. The car has been breaking piece by piece since I bought it, so I wouldn't be surprised if it was exactly that.

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My Primary Driver - '85 300CD - 4-speed conversion, 2.47 rear, lowered, euro headlights, rebuilding (not restoring so much)

Wife's - '08 Saab Sportcombi Aero

Riding a '03 Yamaha Warrior