CC Experience: 1990 Mercedes 300SE – The Realities Of Purchasing And Living With A Low Mileage Classic

(Ed. Note: Please welcome David Devereaux to the ranks of our contributors with this first submission)  In the summer of 1990, Mr. B walked into Stead Motors, a Mercedes-Benz dealer in San Francisco’s East Bay Area. There he purchased an S-class in Garnet Red off the showroom floor. Unlike many Mercedes buyers of the day, Mr. B was not one of the dot-com boom newly rich; Mr. B made his money by starting a thriving beauty products business. In 28 years of ownership, Mr. B put a grand total of 79,000 miles on this 1990 Mercedes 300SE. This is the story of what it is really like to live with an original owner classic car after I became the next owner.

In May of 2018, I had one summer left in Sacramento before I moved south to Cal Poly Pomona. I was between cars, in need of reliable transportation across LA and my stepdad Mike surprised me. As with all car guys Mike enjoys an evening Craigslist hunt, this time he found this Mercedes for sale in Stockton, California for $5,500.

While I was busy detailing Fords at work, Mike drove out to Stockton, saw what a gem this car was, and left a deposit. When I got home from work I apparently had a car! Three days later we were off to pick it up, and I could not have been happier. I spent the rest of that summer paying Mike back for the car and experiencing the reality of a low mileage classic car.

This may not be readily apparent from the sensational ads about low mileage original owner cars, but low mileage cars tend to be neglected. Since coming under my care, this car has needed new motor mounts, a new radiator, three oxygen sensors, a driveshaft bushing, plenty of new hoses, and lots more besides all of that. This car was by no means abused, but it did sit a lot. As is common with cars that aren’t used enough, this old Mercedes needed some work to be at its best.

Despite costing over $60,000 new in 1990, this particular S-class is actually the entry-level model, with a short wheelbase and a straight-six engine under the hood. Provided everything is in order, the engine generates enough power to haul this two-ton brick up any hill.

However, with only 170 horsepower on tap from 3 liters, my understanding is that these gas Mercedes sixes are busy engines with a tendency to blow head gaskets. With this in mind, the first big job I did was to replace the fan clutch and radiator. With the new cooling system, this car has never given me cause to worry, especially in LA’s notorious traffic. Amazingly, despite Mercedes’ reputation for complexity, the radiator was surprisingly intuitive to change.

In typical German fashion, the fuel injection system this car is equipped with is complicated. This system is an electronic-mechanical hybrid similar in function to the injection system used in Mercedes diesel engines.

Like all diesel engines, this gas-powered Mercedes needs a constant supply of high-pressure fuel, especially for smooth cold starts. However, after 28 years the fuel system was no longer capable of maintaining fuel pressure after shutting the car off, making this old car difficult to start from cold.

Unlike the radiator, the one little valve responsible for maintaining fuel pressure was a gigantic pain to change. Working on a fuel system inevitably involves getting wet, and more than a little high. Only 20 dead brain cells later, and the entire fuel pump filter and pressure valve assembly were out of the car. After a long search for copper gaskets, and a tedious reassembly process, the fuel leak was fixed, and the car started beautifully.

Unfortunately, this didn’t last, I have since fixed another fuel pump leak, and the car still doesn’t start very well in the mornings. However, small irritations like a fuel system that does not hold pressure are commonplace in classic car motoring.

Over the years I have found that making an old engine run at high speed is easy, reaching the red line is a cinch. Getting an old car to idle smoothly is an altogether more frustrating and elusive achievement.

By far the most frustrating issue I have fought in this car is code 17. Code 17 is the OBD1 code for the oxygen sensor, by far the most irritating piece of the injection system in this car. I have replaced three oxygen sensors in this car in a year.

The first sensor used a cheap wire splice system that kept vibrating loose until I ditched the splices for solder. The second oxygen sensor was salvaged from a junkyard E-class that worked well for an admirably long time. But at last, I finally installed a factory original plug-in oxygen sensor that is working perfectly.

As annoying as the oxygen sensor fiasco has been it could have been much worse. Unlike modern cars, the computer system and all of the warning lights on this car can be read and reset with one button under the hood.

Original owner classic cars attract lots of attention on internet auction sites in addition to breaking sales records. However, original owner classics are not trouble-free cars. The less mileage that is on a car, and the older a car is, the more seemingly unnecessary work it will need. This Mercedes needed a lot of work, however now it is an amazing machine, comfortable, with effortless style, one of the best daily drivers ever built.