Hi everyone,
I have a 1983 300D Turbo sedan which is in great shape except for a vacuum leak that I suspect. When I'm driving, there's a really noticeable droning sound, like what you'd think sitting in a prop commuter plane sounds like. The sound is only when I'm moving, not when I'm idle. I originally thought this might be a bearing problem, but I also noticed that my door locks don't work when the car is off, and the cruise control pulses the accelerator. I know that the door locks and the cruse work off vacuum so I figure that maybe my sound is also a vacuum leak. Also, does the vacuum do anything to the transmission? It clunks a little more than usual. Where are common places that I should for this leak? Is it a vacuum pump? Is this presumed vacuum problem pretty typical? I hate it when my car has awkward sounds so this really bothers me. Any advice would be really great. Thanks!!!

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1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside