Introduced nearly 40-years ago, the Mercedes-Benz w123 series is quickly making the transition from a cheap daily driver to a classic car that is worth restoring or, at the very least, preserving. Clean examples are starting to sell for lofty sums and enthusiasts are snatching up affordable ones while they are still reasonably priced.
Drawing from experience acquired over years of owning, driving and fixing w123s, we’ve compiled a quick list of issues to look for when buying one. This is far from a comprehensive list because each model has its pros and cons and, of course, each car is unique and will have developed its own set of problems over time. What you’ll find below is merely a general overlook that aims to guide potential buyers in the right direction.
Don’t be fooled into the notion that the more expensive a car was when it was new the less likely it is to rust 30-years later. All cars built with steel rust, ranging from the cheapest Yugo to the most expensive Rolls-Royce, though some admittedly do it better.
Mercedes w123s often start to rust around the wheel arches, around the jack points, at the bottom of the doors, around the rear window and on the front apron. Later models were better rust-proofed than earlier ones but that doesn’t make them immune to the issue, and the tin worm has forced many w123s into an early retirement.
2. Leaky door seals
On sedans and wagons, the door seals are thin towards the top and they have a bad tendency to crack over time, letting water and humidity in. Both can wreak havoc on an interior if the seal is not replaced in a timely manner: Humidity will pit chrome parts while water will ruin the carpets and eventually attack the floors if enough of it builds up.
The seals can be quickly patched up by gluing part of a bicycle inner tube over the cracks, but they will ultimately need to be replaced. New seals are available either through Mercedes or from a growing number of aftermarket parts vendors.
3. Instrument cluster issues
The odometer is notorious for failing on all Mercedes built in the 1970s and 1980s. If you’re looking at a cheap car with low miles, drive it around long enough to make sure the odometer actually moves. One of the tell-tale signs of a non-functioning odometer is a driver’s seat that is more worn than the mileage would suggest.
Conversely, we’ve seen some w123s (and w126s) where the odometer goes up faster than it should.
Additionally (and unrelated to the odometer), the gas gauge can be jumpy or stop working altogether, which is a less problematic than above. Running out of fuel once will generally convince you to either fix the gauge or keep a close eye on how far you’ve driven between stops at the pump.
4. Vacuum problems
The w123 uses an extensive vacuum system that controls numerous functions ranging from the power door locks to the way the automatic transmission shifts. Minor vacuum leaks can be straightforward to track down with the right tools, but getting to the bottom of bigger issues can be a painful process whose length can be measured by a geologic time scale. Cars living in hot climates or who have been sitting for a long time are more prone to vacuum issues.
5. General tiredness
This is worth pointing out because w123s have a reputation for being bullet-proof. They’re more robust than other cars built in the same era but maintenance is not an option. If you’re looking at a w123 that appears to be on its last leg (rusty, low oil pressure, worn out interior and so forth), it probably is and we suggest you pass on it unless it’s a hell of a deal and you’re willing to take on a project.