Are these older Mercedes like 1985 300SD worth anything and fun to drive as an antique or a total money pit?
Rear wheel wells have rust, as well as some other small quirks and body shows it's age too.
Appreciate any insights
They'll run and drive with a real minimal amount of effort, but take tons of money to get absolutely perfect.
They are definitely fun in their own way. If half the stuff works it'll be cute and quirky.
Stuff like fuel filters and brakes are readily available and cheap. The diesel engine is legendary and typically you find these out of tune and in need of valve adjustments and other fiddling.
I have an 84 300d. It's pretty slow but very cool. The suspension is soft and it's fun to bomb around in. I imagine an SD will be even slower but these engines were never about speed anyway. There is a line that goes from the intake manifold to something called the alda I think? It gets plugged with soot and can limit fueling and therefore performance. Rust is definitely something to look out for. Inspect the sun roof drains, drains in the engine cowel, behind battery for rust, jack points ect. 1985 model may have different turbo and transmission than earlier years I'm not sure. I'm only talking from w123 chassis experience. How many miles and how much money? On the plus side I always got 25-30mpg hand calculated.
W123 and W126 are great cars. The pre-1985 cars are probably the longest-lasting vehicles on the road.
I wouldnt hesitate to drive my 81 240D or 82 300CD across country tomorrow.
The W126, like yours, is kind of the epitome. The W126 chassis is a little bit newer, offers some better capabilities over the w123, and still has the OM617 engine. Granted, the 85 617 engine has a few nuances like the Klima relay and a different tach sensor approach... i.e. a few very simple computers...
These vehicles were made very strong and with good steel, but they didnt have the rustproofing that newer vehicles have. So rust can be quite common. Sometimes it is repairable, depending upon where it is located. Sometimes it is expensive. But this is the case for any car, from any manufacturer. When rust shows, you need to cut out and weld in new metal.
The W126 did have issues with rust around the rear windshield seal. Rust will form there. Rust will also form in wheelwells like any other car. If seals are bad, rust can form from in the trunk too.
How is parts available at typical stores? Say what you will, but if you're going cross country, waiting for mailorder is a bit of a hindrance. Even if you buy the dimestore caliper/hose/whatever only to replace it when you get home with the proper part, that is still better than being stranded.
What's the definition of fun? For some, just cruising along at low speeds is fine, others are expecting razor sharp handling and space shuttle acceleration. Gotta have metrics here--and, if I'm not mistaken, these cars were slow in their day--let alone today.