I'm looking at a 1983 Mercedes 300SD with 137,817 miles on it. He's selling it for $1,400. It is currently inspected until the end of next month (April). What should I be looking for/at? What are the right questions to be asking (if I had ever owned one I might have a clue)?

Help please...

Any type of alternative fuel system(Often kills the engine)

Try a cold start(cold engine) to really see what shape it's in. Check the boots on the rear axle half-shafts. There is other stuff, but you might want to do a search, it has been reiterated 500 times in the diesel section

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

Make sure the AC is working and also the electricals. They can be a real issues when something goes wrong with the AC and heat.

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2015 ML350 4Matic. Wifes DD
2015 GLK350 4Matic. My winter DD
2012 E350 4Matic. Road Trip car
2009 CLK350 Coupe Designo.Kleemann Tune For nice days/DD
2006 CL600. V12.Eurocharged Tune. Enough said
2005 CLK55 AMG Coupe.Kleemann Tune. For the sound and style
2004 CLK320 Cabriolet. 2005+ Interior swap. For the sunny Florida days & beach days

What's it look like? What condition?

$1400 is cheap enough, but, Carfax it....MB odometers from that era usually were broke half the time.

Check condition of seats and pedals to see if 137k is truthfull or not. Ought to look pretty good with no sagging in the seat or displaced seat noodles (ribs) and pedals, shifter and arm rest should show minimal wear.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Post that question in diesel discussion.
And get ready to read

See:

http://home.concepts.nl/~vlimmere/tips.htm

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.