Inside the Factory That Built the W123: How Mercedes Made a Car That Outlasted Its Owners

This is the Mercedes-Benz plant in Sindelfingen, Germany, in the 1970s. The total area: around 2.9 million square meters. That’s roughly the size of 400 football fields. It was — and still is — the largest Mercedes-Benz plant in the world.

And it’s where the W123 got made. Not designed. Not marketed. Made. By hand, mostly, by people who earned between 2,000 and 3,000 Deutsche Marks a month — the equivalent of $1,800 to $2,500. That wasn’t just good money in the 1970s. That was excellent money. Enough to provide for a whole family on a single income.

Insane, right?

Where Every Car Began

Every W123 started in the same place: workers feeding steel into giant machines that pressed down with over 1,000 tons of force. The noise was incredible. And out came the body panels — floors, sides, roofs, doors.

At its peak, over 30,000 people worked at this plant. Around 22,000 of them were hands-on, right there on the assembly line. These weren’t just workers. They were craftsmen. Many stayed with Mercedes their entire lives. They’d wake up, drink coffee, put on their uniforms, and walk into a plant that was known across Germany as one of the best places to work.

Workers began by assembling the car’s floor, sides, and roof. They had to be precise. If one part was off by a few millimetres, the whole body could end up crooked. Mercedes didn’t allow mistakes like that. Every piece had to fit just right. And almost everything was done by hand.

A Thousand Welds and a Lot of Patience

To make the car strong, over 1,000 welds were added to each body. A weld is where two metal parts are melted together so they stay connected forever. Even though robots were used, humans still did most of the work — especially in tight spaces and areas that needed extra care.

Workers checked everything by hand. If a weld didn’t look right, they fixed it immediately. The car couldn’t move to the next step unless everything was perfect. That was the rule.

This part of the process also determined how safe the car would be. The W123 had extra-strong roof pillars, floor panels, and door frames. These parts were made tougher than usual to protect passengers in a crash. Back then, airbags were rare. The body had to be solid.

In the late ‘70s, the average monthly gross wage in West Germany for industrial workers was around 2,200 Deutsche Marks. A brand-new W123 in 1976 cost about 22,000 Deutsche Marks. So a well-paid factory worker needed nine to ten months’ salary to buy the car everyone was loving.

The Rust Proofing That Made Them Last

Once the body was welded and shaped, it was lifted by a special rail system and moved into a large chemical bath. The whole thing was dipped into a liquid that stopped rust from forming. This liquid got into all the small spaces — even areas people couldn’t reach.

That dip made sure the steel wouldn’t rust from the inside out. Today, many factories still do rust protection, but it’s often done faster, and some cheaper brands use thinner coatings. Back then, Mercedes did it the slow, careful way. That’s why even today, many W123s still don’t show rust.

After the dip, the car moved into the paint booth. Most of the painting was done by hand. Trained workers made sure the colour was even and smooth. Mercedes offered many colours — white, black, beige, gold, silver, and even greens, blues, and bold reds. Each car was painted carefully, one at a time. Then it was rolled into a drying oven. The heat made the paint stick better and gave it that smooth shine.

Engines Built by Hand

While the body was being painted, something else was happening in a different part of the factory. The engine was being built.

Mercedes didn’t build engines on the main line. They had a special engine workshop filled with senior workers who focused on one thing: making sure each engine was perfect. At that time, there were several engine options. Some were gasoline. Others were diesel. The most famous was the 240D — a slow but nearly indestructible diesel that could go over 500,000 miles with no major problems.

Workers started by assembling the engine block, the core of the engine. Then they added pistons, crankshafts, and more. Everything had to fit just right. Most of this work was done by hand with tools. Today, engine assembly is mostly done by robots, with only a few people checking things. That’s faster, but it means less human attention to small details.

In the 1970s, every engine was touched by real workers who had years of experience.

The Marriage

Once the engine was fully built, it went through a test station. If it passed, it was sent to the main assembly line to wait for the rest of the car. By the time the engine was ready, the painted body was done drying. Now it was t ime to bring them together.

In the car industry, this moment is called the marriage. It’s when the body and the chassis become one. The chassis was rolled in first. The painted body was lowered down from above using a large crane. Workers carefully lined everything up. They made sure every bolt and connection matched perfectly.

This step had to be done slowly. If even one wire or pipe wasn’t connected properly, the car wouldn’t work later on. That’s why workers double-checked everything.

Back then, this was done by a small team of skilled workers. Today, in modern factories, it’s done almost completely by robots.

Forty to Fifty Hours Per Car

Every car took about 40 to 50 hours to complete. Compared to today’s factories, which build cars in 20 to 30 hours, the W123 took more time because so much of the work was done by hand.

Interior installation was another hands-on process. Mercedes offered different seat options. Each seat was heavy and firm, made to last for years without sagging or tearing. Workers installed the back seats first, then the front. Every part was fitted carefully by hand.

Then came the leak test. The whole car was placed in a special room and sprayed with water, almost like a car wash. A worker sat inside with a flashlight, checking every corner for leaks. If even one drop of water came in, they fixed the problem.

And then the big moment: the first engine start. Workers turned the key and listened closely. Was the engine smooth? Were there strange noises or vibrations? They checked the exhaust, the temperature, and how the engine responded when revved. After that, the car was rolled onto a dyno — a machine that let the car drive while staying in one spot — so workers could check it exactly.

There were slogans on the walls: Das Beste oder nichts. The best or nothing.

Why They Don’t Make Them Like This Anymore

If the W123 was so good, so reliable, and so loved, why don’t they make cars like that anymore?

The answer is simple: priorities changed.

Back in the 1970s and early ’80s, Mercedes built the W123 to be strong, safe, and long-lasting. They spent many hours building each car by hand. The company wanted every car to live a long life.

But today, car companies think differently. Most cars are built to last 10 to 15 years, not 30 or 40. Why? Because people replace their cars more often. They lease. They upgrade. They want new features, new tech, and new looks. That means car companies don’t have to build things that last forever.

In the 1970s, a worker might spend over 40 hours building just one W123. Today, many modern cars are built in half that time. That saves money, but it also means less personal care goes into each vehicle.

Modern cars also have to meet strict rules for fuel use, emissions, and crash safety. That’s a good thing, but it means cars are packed with sensors, wires, and software. Those things can break, and they’re harder to repair.

And let’s not forget the business side. Car companies today want people to buy new cars often. If your modern car wears out in 10 years, that’s good for business. In contrast, W123 owners kept their cars for decades — and that didn’t help Mercedes sell more cars.

Still, many people miss the old way. They miss cars that were simple, strong, and made to last. The W123 is a reminder of a time when quality came first. Before speed. Before gadgets. Before profits.

Can You Still Buy One?

Yes. You can still buy a Mercedes-Benz W123. But prices vary a lot depending on condition, model, and location.

A basic W123 that runs but needs work might cost you around $5,000 to $10,000. These are usually high-mileage cars with faded paint or worn interiors. They may not be perfect, but they’re still strong underneath.

A well-maintained W123 with a clean body, nice interior, and working engine will likely cost between $12,000 and $25,000. These are often daily drivers — cars that have been loved and taken care of over the years.

Then there are the collector-quality W123s. Restored or kept in almost-new condition, sometimes with very low miles and original parts. These can sell for $30,000 to $50,000 or more, especially rare models like the 280E, 300D Turbo, or station wagons with third-row seats.

Germany is where most W123s were sold and still survive. Some of the best examples are still in German garages, often owned by older people who kept them clean and original. California is another great source, thanks to the dry weather and strong Mercedes community. You can also try Bring a Trailer, Hemmings, Classic.com, or AutoScout24.

Before buying, always check for rust, engine health, and interior wear. Even though the W123 is tough, time can still take its toll. A proper inspection can save you a lot of trouble.

So yes, the W123 is still out there. A car built with care, made to last, and still turning heads today. The only question is: would you buy one?