Each year people ask me about how to start their Mercedes diesel engines in cold weather. I usually end up dispelling myths in addition to giving advice. I decided to write an article to look at some of these myths and back up some good advice with facts about how the starting systems in these cars are designed to operate.
For simplicity, I will use a 1983 300D Turbo diesel (123.133 with OM617a) as a basis for this article. The same theory and functions apply to a wide range of Mercedes diesels from the 1970s through the 1990s.
Myth: “When the preglow indicator goes out, the engine is ready for starting”
This week I’ve enjoyed driving my 1979 300SD everyday while we’re down one car with my wife’s E320 in the body shop. This car only sees a few thousand miles a year, and goes into winter storage when the weather turns cold. But when I do drive it, I drive it a lot. Weekend trips to the shore, or the occasional daily commute. Long highway trips are good for the car, allowing everything to get up to running temperature.
Using the car for daily transportation gives you a great appreciation of how well engineered it is. The car is one of the earlier 300SDs produced, with a 110hp 5 cylinder turbo diesel and automatic transmission that starts in second gear from a stop. (Later cars had 120hp and a first gear start.) The result is a relaxed driving experience, but more than enough power is available to keep up with modern traffic. The car has excellent passing power in top gear on the highway, pulling from 70 to 80mph without much effort. Pressing the accelerator to the floor from a start yields a kickdown into first and somewhat more spirited acceleration, and some help getting up steep grades.
Everything works on this car, which really adds to the joy of driving it. The climate control does an excellent job keeping the cabin comfortable in weather like this… mid 70s, humid. It mixes just a bit of warm air with the air conditioner to keep things dry and cool. The vacuum operated cruise control holds your speed nicely on the highway. Ride and handling, as well as the brakes, are excellent. If you choose, it can be driven quite aggressively and fly through the curves. The occasional rain shower has been no problem, its very confident on slippery roads as well.
Additional pictures of this lovely car can be found here.