My new/old bio beater, a 79 300SD, has a vacuum leak that causes the car to stay running after the ignition is turned off. We have to lock the driver door and wait for the car to die to get it to turn off,
The mech we got the car from says he's been driving the car that way for a couple years and just wasn't interested in trying to figure out where the leak is.
Where would you start in looking, replacing hoses etc to make this stop.

We're going to make this a project car over the next year or so and return her to former glory. No one should have let a MB get in this condition.
The engine runs well, the mech upped the HP somehow and it's got nice pick up compaired to the 78 300SD we also own.

Thanks for any help/advice you can offer.

Ginny in Denver
78 300SD, Mint Bio Baby
79 300SD Bio Beater, new to us

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Ginny in Denver-ish
78 300SD, 265K (mine)

Do a search...Vacuum.....it's all here, in varoius places....

SB

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Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

Having been owned by a PO's trashed 79 300SD and your statement of more HP than expected, I would look at the over boost switch gizmo on the firewall that conects to the ALDA and ALDA adjustment.
Post a 0-60 time so we and guestimate the PO's tweaking. A two ton road Panzer should roar past 240d's with a 16 to 18 second range. If severly tweaked, 14 seconds. If VERY tweaked ... not a daily driver. Mine is 16.5 seconds, slightly tweaked, burning 50% 1 micron WVO, 40% diesel & 10% RUG.
Any mech. who can not fix diesel shut off is not a mech. Watch out for his other creative !@#@!@$X. A quick fix is to install a roughly 100 ml syringe on the ignition vacuum line and just pull to stop! You probaly have a few 27-28 year old rubber connectors that are less reliable than political promises (sorry, it's that time of year again). Diesel Giant has the advice and parts.
Good luck. There is nothing like the feeling of a two ton, classic MB costing pennies per mile. It's the opposite of finding out the PO never cleaned out the trash in the hood hinge well.