Every single 300D is worth rescuing
Nicknames like the “Million Mile Engine” didn’t happen because some persnickety owners got a reliable car. No, the engine in the 300D was awarded such a nickname for its incredible durability. A testament to “they don’t build them like they used to.” It’s the OM617 of course, and YouTube’s Car Wizard discusses how these engines – and the car they are in – stand up on the used car market.
The PERFECT Restoration Plan on this ’84 Mercedes 300D
The example as shown here is a 1984 300D, which will be typically what you find in the W123 range. You can get coupes (C123) and wagons (S123) but most are the sedan. You’ll have one of two engines. The turbocharged or non turbocharged OM617. This condition will be typical of what the market will yield.
The Wizard covers a few inspection points in this video, but they are mainly related to the age of the cars. Any 40 year old vehicle is going to have older components that are prone to wear and degradation. But overall the 300D in question is still worth saving. And most of them are. So if you’re in the market for a W123, we consider the following pieces of advice worth while to follow.
Safety is a main priority, and should always be addressed first. It doesn’t matter how wel your engine runs without any leaks if your brake lines are about to burst. So we’d tackle the braking system first. Rubber brake lines can get brittle and crack, but master cylinders can also develop internal leaks and fail, especially with vacuum assist brake boosters.
After that, you’ll want to make sure all 4 wheels stay on the ground, and pointed in the desired direction. We’d assume bushings and ball joints will be bad on any W123 you buy. And if they aren’t you’ve got a great deal. Shocks are worth doing “while you’re in there” too. And hey, don’t forget about the engine shocks.
At this point, you have a “rolling restoration.” And can address any issues the engine has with leaks, while knowing that any test drives will be done safely. Seals on the engine are going to be approaching 40 years old or older. You’ll have leaks and seepage. You’ll now exactly where you parked your car based on what it has left behind. But you’ll still have a car that’s way cooler than many modern cars.
