COAL: 1988 Mercedes Benz 300SEL – Does Size Really Matter?

(White 300SEL shots are of my younger son’s former car, which met an untimely death by his hands, but not before I had a chance to drive it. A story for another time. – PN)

When we last left off, the dark blue 300D turbodiesel had been sold to a local surveyor friend. I had not identified a replacement “rescue” COAL yet, but I had in mind to find some type of W126 Mercedes S-Class. I really liked these, and by 2002 or so when I was looking, they had been out of production for over 10 years, and some cheap ones could be found.

The 450SEL I wrote about before was part of the W116 S-Class series, from 1972 to 1980. The W116 was the first body to be referred to as an S-Class, though the W108/109 before it is considered by many to be an S-Class. The W108 just wasn’t typically referred to, or marketed that way.

I actually have a W108 now, a 1970 280SEL I have owned for about 12 years. I’ve never used it as anything other than a weekend driver, but I’ll have to write it up at some point. It’s in a garage in an old country house we inherited about 90 minutes away, so I don’t play with it very often unfortunately. But, I’m thankful to have a free place to keep it inside.

One day on my way to an adjacent county, I passed the small used car lot owned by the retired Florida car dealer. This was the same lot where I stumbled upon the dark red, nonturbo 300D. And lo and behold, he had a long wheelbase W126 of some sort. Like the W116, the W126 was sold in the US in both short and long wheelbases.

Short wheelbase, note the slender chrome trim piece between the rear door panes. Also, this is a pre-facelift version with fluted plastic cladding and Bundt wheels


The turbodiesels of both were generally the short wheelbase (300SD with the legendary 5 cylinder turbo), except for the last few years when they went long (300SDL with an inline six turbodiesel that could be troublesome). The gas V8’s were generally the long wheelbases, though the 380SE of 1984-85 had the short wheelbase.

I could tell his was a long wheelbase by the painted trim piece between the rear door glass that lowers, and the fixed glass pane in the rear door. On the long wheelbase, this piece was wide, and painted body color in the middle. On the short wheelbases, it was just a chrome piece. It was just an easy way to tell at a glance which one you were looking at, as the greater overall length wasn’t always immediately apparent. The wheelbases were only about 5 inches different, 115.6 versus 121.

It also had the smooth plastic lower cladding, “new style” wheels borrowed from the 1986-on E-Class, and flush headlights. So, I knew it had to be a 1986-1991 model of some sort. I was excited to find a 420SEL or 560SEL, so I thought. I was surprised to look at the trunk and see 300SEL displayed.

I don’t think I had heard of a 300SEL at that point, at least not in this body. It was a gasoline straight six, the same 3 liter engine used in the lighter W124 300E, but here it was installed in the long wheelbase W126. Wikipedia says this was one of the lower quantities of the W126 body, about 40,000 sold worldwide from 1985 to the end of the series in 1991 or so. For contrast, the pricey and top of the line 560SEL was almost twice as common, about 75,000 sold.

With 178 horsepower, the 300SEL wouldn’t win any drag races then or now. But after the two diesels, it felt peppy enough. And at the time it was built, there was much less equipment (safety or entertainment) on board. With one driver side airbag and antilock brakes, the long-wheelbase 1988 300SEL only weighed 3,417 pounds! My 2016 Lexus ES350 COAL from last week weighs right about two hundred pounds more, on a ten inch shorter wheelbase. But, it carries ten airbags, and equipment not available on any car at any price in 1988.

As an aside, the 300SEL new car sticker was $56,250 in 1988, or about $117,600 today. It’s interesting to see how much more equipment your dollar buys you today. In 2002 or so, the 14-year-old 300SEL I was looking at was priced at $3,000, or about $4,500 today. And indeed, you can find serviceable 2003 S-Classes for $4,500 or so now. In fact, I see a 2001 S55AMG for $4,800 online right now! Good grief, someone buy it before I do.

It didn’t look quite this good, but it was this exact color and overall appearance.

I could see that this was probably a car he had brought up from Florida: the interior looked OK, but the champagne colored paint was rough and faded though the car barely showed 100,000 miles. The bumpers were losing their paint and the rubber itself was showing. When I caught the man in the office, he said it had no wipers, so he wasn’t sure he could sell it. No wipers? The fuse had been removed from the wipers to prevent further damage, but he thought it needed a “wiper transmission”. Oh, and it had no heat either. The blower came on, but it never got hot.

I offered him $2,000 cash and he accepted. I thought I could fix the heat myself, but the wipers had me stumped. I knew I would have to get that figured out quickly, as I had to pass state inspection to get a tag, and I couldn’t risk getting caught in the rain, either!

The heat sure enough turned out to be the coolant valve assembly, what Mercedes calls a “duovalve”. These are common problem points to the Mercedes climate control system; this was part of what I paid someone to figure out with the dark blue 300D that had no heat. This controls the flow of coolant to the heater core, based upon input from the temperature wheel. There is a little rubber diaphram inside, and when it fails, the electrical parts flood and that’s the end of the duovalve. It can fail closed so you have no heat, or fully open so you have unrelenting heat, or any point in between. About $100 new, I replaced it myself in a few minutes (it’s up high on the firewall, easy to reach) and crossed my fingers. We had heat!

The wiper research concerned me. This Mercedes body did not use an articulating arm like many newer Mercedes, but it did have an unconventional arrangement where both arms mounted near the center of the cowl. Nowadays, there are a lot of online videos and tutorials about “W126 wiper failure” and it’s apparently quite a Rube Goldberg type of linkage. This video is one of my favorite Mercedes sources, Kent Bergsma, who has a lot of very helpful YouTube videos. A W126 wiper transmission is on the bench in front of him.

This is a W116 S-Class, but the wiper arm arrangement is the same as the W126, and this was the only image of them in action I could find. You can see the somewhat unconventional action; these are not quite fully deployed. The thinking I believe was that the water would be coming off the blades parallel with the airflow; and you would not have all the sloshing right in front of the driver’s face as you might see with a passenger arm that reached over into the driver’s field of vision.

Here’s another shot of W126 wipers at rest. So, the location of the transmission was not readily apparent. The pricing I was seeing fifteen years ago was $700 plus, as well. So I was worried I had a major expense on my hands, if I had to pay someone to figure this out.

My first stop was to replace the missing fuse, and see what happened. Once I had the fuse in, I turned them on. They fully deployed properly, but on the way back down, the passenger arm moved much more slowly than the driver side arm, and they therefore collided and became intertwined. Gee, that’s not good.

I flipped the cover over the mounting nut up, removed the nuts, and removed the arms to untangle them. They didn’t seem to be tightened down very well. I reinstalled them in the park position, after running the motor with the arms off to get the shafts to return to the “park” position. I tried the wipers again, and they worked. Worked just fine, not getting close to being tangled. They extended fully and parked correctly. I never had any more trouble from them, and I surmised that apparently the problem all along had been simply that one or both arms were not tightened down sufficiently. So, that fix was free!

I like the 300SEL so much I thought about getting it painted. I got an estimate or two but was too busy to follow through. The bad paint condition was really the only meaningful problem, after I had fixed the heat and wipers. The AC, stereo and cruise control all worked fine. It did get very poor mileage, I don’t recall ever getting out of the teens under any circumstances.

I installed a set of Michelin Symmetry radials, which were not sporty but rode quietly and smoothly. The rear resonator was a little loud and quickly got worse. It was just an old fashioned, round muffler, not a custom or specific fitting piece like a lot of newer cars. My local tire and exhaust place replaced it and fashioned a new tailpipe to look as original as they could muster.

My thoughts about keeping the 300SEL and painting it were dashed when, you guessed it, I was seduced by another rescue COAL we will read about next week. I parked the 300SEL in front of a bustling new all-you-can-eat buffet with a for sale sign on it, asking $4,500. The first person who called me about it was a nice older retiree, who had always dreamed of a big Mercedes. Here was an affordable and good running one at a reasonable price, and it went on to a new home in better shape than I had found it.