Yet another side-of-the-road car. This a beige 84 300SD w/240K miles. Interior back is kind of bad, seat cushion back sort of coming apart. Carpets look pretty clean, wood's good as are the front seats. Lots of surface rust around trim pieces but no holes that I can see. Underneath looks really very clean and unrusted. Asking price is 2K. I am considering taking the car out for a spin and am wondering what to look for as far as performance and mysterious noises. I've got 2 other diesels, an 83 300D and an 83 300CD so I'm sort of familiar with them. Any SD specific things I should be looking for? I'd be selling the 300D to appease the wife. I've heard here the SD is a much better car then the D, how so? Ride? Reliability? Isn't the car essentially just a bigger D? Advise sought and greatly appreciated.
Thanks.

I think you will find this car basically the same as your 123s except for the difference in the 126 body style. The motors are almost identical and the power and everything else seem the same.

Check the blowby and other usual issues with these cars. ACC controllers are bad in both my 126s and the way I could tell is that the foot vents didn't open. I also had a chance to put a known good unit in and everything worked. Also had a bad monovalve that could be told by not giving heat, then cool when the wheel was rotated.
Also AC work could get expensive.

I've found though in going through my 2 new SDs that they are basically the same and the same rules apply.

Driveability wise you get more float in the 126 than the 123 in my opinion. Mommy likes this big car feeling.

Does this one have the chrome surrounds on the wheel wells? Brioken springs in teh drivers seat are another common malady of these cars. I replaced one spring box with a welded toghether one out of a 123 and it was almost the same. Had to make a few minor adjustments with a hammer but it worked.

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique

Yeah, what he said.
HVAC prob's seem to be the most common with these. Get one vacuum leak, and nothing works right. I went around the problem by just pulling off all the dash panels and manually setting the air flap-valves to where I got air out everywhere I wanted. Has worked just fine that way for a couple years now.
Haven't ever ridden in a W123, but do love the comfy ride of my SD. Great hiway cruiser

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past MB rides:
'68 220D
'68 220D(another one)
'67 230
'84 SD
Current rides:
'06 Lexus RX330
'93 Ford F-250
'96 Corvette
'99 Polaris 700 RMK sled
2011 Polaris Assault
'86 Yamaha TT350(good 'ol thumper)

Rick,
I gotta tell ya, what a stroke of simplicity/genius! Just wire the darn things the way you want and leave it alone...

__________________
'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique