scubahood86,

Keeping your W123 Mercedes Diesel in a condition you will proud of will be a chore at times, and you seem willing to take on the chore. The selection of your vehicle will be critical to deciding how much of an unpleasant or pleasant experience fulfilling your committment will end up being.

In my experience, the worst enemy of these cars is rust. Restoring the car after it has been allowed to physically decay is often costly and subject to the skill of the person performing the body restoration. The next issue is the general condition of the engine. the best barometer of the internal health of the engine is a compression check, dry and wet, and possibly a leakdown check if there is a sign of a loss of compression.

So, look for a car that has a solid body, first. All the mechanical stuff can be dealt with, including the engine with regular mechanical skills, some persistence and a few bucks, on a schedule that usually is dictated by the owner.

Read some of the threads here on rusting of W123's, but the most serious problems come from clogged drains around the firewall, doors, trunk, and if you have a sunroof, in the "A" and "C" pillars. Rotten rubber seals on the windshield and rear window can let water in and run to places never equipped to resist or separately drain the leakage out of the car before it causes problems.

The rocker panels where the jacking tubes are located, and the battery tray are also weak links. The battery tray problem can be traced to poor battery maintenance, allowing acid overflows that run down to the tray and the structural metal in the whole area. This can be a big deal to fix, as once you remove the obvious stuff, more bad news is uncovered.

The drain lines that clog, or front and rear window gaskets that leak, force the flow of water from rain and melting snow to be redirected from the designed path to the ground. This often results in a path that involves the interior floor boards, front and rear, of the car. When the floor boards rot away, this can be a big deal too. So, you should pull the rugs up and carefully look for signs of water damage to the rugs, and to the condition of the floor boards below them. I believe the front and rear footwells are equipped with little drains themselves, so you should check to see if they are clear or clogged too.

The front and rear fenders often succumb to corrosion as well, and if this is caught before the corrosion starts spreading to the adjacent, structural supporting steel, it is a pain, but not as serious as it could be.

If the body is good, and the interior as well, a car with a bad motor may be cheap enough to make an engine rebuild, or a rebuilt replacement engine, a great starting place. Takes a little longer to get it on the road and in daily use, but it may be the most reliable option in the end.

I guess the message is be picky, take your time and find something worth all your effort to keep in great operating conditions for another two decades. Good Luck!

Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Lemme answer your question this way. I live in the southern section of the country. No salt on the roads to rot a car in winter. I bought a 22 year old car with the intention of keeping it for the rest of my life. I'm 31 years old. Same thing for my Dodge Ram pickup. I bought the Cummins for the same reason. I will never drive enough miles in that vehicle throughout the lifespan of that engine to wear it out. The Dodge is now paid for, three years early to be exact. That is one of the best feelings one can have. I will of course buy other vehicles in the future. I want this to be a choice instead of a need, and my "lifetime cars" will not ever be traded in for new ones. What I've learned from my car in the short period of time that I've had it so far, is that the W123 cars are literally built to last forever if you take care of the routine maintenance items.

Arent 80-85 300ds's the w126 type? If so will this greatly differ from the w123 or will there just be a few minor changes.

I have a furter question also, what is a good way to compare parts prices between the 81-85 300SD (w126) and any 1995 and later domestic/jap car. This would be greatly appreciated and US sites will be fine but any Canadian sites/places would be great.