So have you ever wanted to experience a diesel? A German diesel straight from Deutschland? Well here was my attempt and wow there's a lot to say...

So, this was my 1992 Mercedes-Benz 300D.

Yep... The "D" means diesel. Under the hood of the sedan is a 2.5 L inline 5 cylinder turbo diesel; the OM602. A nearly unkillable power plant just like the rest of the Mercedes diesels paired with the four speed automatic. These engines were not powerful and the turbo it makes it adequate. We're power wasn't quality was everywhere. Doors closed with the deep thud of a bank vault. The wood trim was not velor. In that generation of Mercedes, the wood trim was wood all the way down to the backing which was just painted black. That wasn't wood trim, that was wood-wood! It was amazing how such a neglected old beat up Mercedes still drove so well. The interior barely worn in with easily over $300,000 mi on it. I was amazed by the quality that Mercedes used to put out. You could see it everywhere in all the little details even deteriorated from sun and rodent damage. Oh yeah? Mice got in this car! That was most of the battle; repairing mouse damage.

The mouse damage was extensive. Whole wiring harnesses were almost chewed through behind the wiper cowl. It was amazing that the car hadn't caught fire and burned to the ground but I guess you can't burn a car down without a spark. And there's no spark plugs in a diesel! 😂 I would eventually work my way through most of the mouse damaged wiring harnesses and stitch them back together bit by bit. Not much changed things that were broken remain broken but, it did feel good too patch all the wiring especially after the loss of one of my cats.

The one thing no one tells you about owning a diesel, is it diesels don't have ignitions. Instead, this diesel engine uses a fuel cutoff to turn the engine off. On these old Mercedes diesels, it is very common for vacuum leaks under the hood to cause the car to not shut off when you take the key out of the ignition. A scary situation! Your car is still running but the key is out of it and all the electronics of the car shut off! On this car, and on many others the usual culprit is the vacuum shut off valve located on the injection pump. Upon inspection, The vacuum shut off valve was perfectly fine on the injection pump. When diagnosing the vacuum system on these diesel cars, it is very handy to have a handheld vacuum pump. That way you can test vacuum on specific lines and figure out if you have a vacuum leak somewhere. The vacuum diaphragm on the injection pump that controls the fuel shut off by the ignition was perfectly fine. It held plenty of vacuum. Tracing the feed line into the cab of the car I discovered that the vacuum switch controlled by the ignition was bad; it did not hold vacuum. I replaced the switch and after a few weeks of driving having to pop the hood and manually shut off the fuel on the injection pump, the car finally was able to shut itself off with the ignition.

The only other major repair I conducted was replacing the trunk latch This was done by ordering a used trunk latch and key. Removal of the old trunk latch was very violent. It had to be drilled out and of course, drilling out always has collateral damage. Scratches, chips, and other remnants of aggressive drilling are present under the trunk latch trim. Hidden but there from a fight drilling out a lock built to last a nuclear explosion. Or maybe my drill bit was blunted? Who knows? 🤷‍♂️.

What about driving? Other than not having a muffler, or downpipe,or any pipe after the turbo for that matter... It drove very well albeit very smokey. This was definitely a car you would have to drive with the windows down just to be able to breathe. Nonetheless, the transmission was paired beautifully with this 2.5 l diesel It knew exactly when to shift how to shift even though acceleration was slow The transmission was fine tuned to use all 165 lb feet of torque this injured could output especially with merging on highway ramp.

Fuel economy was okay. Not great for diesel car. At the cost of diesel fuel, This car averaged about 22 mpg. That may have been good back in 1992, but by 2024 standards that's low. Combined with the excessive amount of oil this engine was burning It was clear this 2.5 l 5 cylinder was very tired and needed a good rebuild. I move this vehicle on to the owner of a 1998 BMW 328 convertible as a straight trade. If given the opportunity, this would be another vehicle I'd like to experience sans the mice damage to all the wiring! To this day no one knows how many miles around this car. The odometer was not original which means if I had to estimate, this car probably has over 300,000 mi.