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Discussion Starter #1

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I have a 1985 300SD around here somewhere, which I haven't driven in a year or two. Those 5 cylinder diesels are serious lumps of machinery. If the seat is not too saggy they are great long distance cruisers. My first SD would poop along at 95 no trouble, and always got 29 mpg, up hill, downhill, in town, on the highway, didn't matter, and that was with over 300,000 miles on it. They do need to have the valves adjusted regularly.

I once took out the drivers seat to do some work on it, and out of curiosity, weighed it. 80 pounds!

If you're going to drive it in the winter and it gets cold where you are, keep your starting circuit in good order. I took my alternator and starter out and to a good local shop for rebuilding. Preventative maintenance is best.

Also keep the crud cleaned out of the banjo fitting on the intake manifold and the valve(mounted on the firewall) on that line which actuates the ALDA mixture controller on the injection pump (I know the turbos have this, not sure about the normally aspirated, or should I say, the normally exasperated)

Transmissions slow to shift or flaring is common while you track down all the vacuum leaks, and you also can adjust the vacuum valve on the side of the tranny, Check out Mercedesshop.com for a very helpful forum 'Diesel Discussion."
 

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300SD, eh? I looked for a diesel W126 for a good while.. never could find a good one. I found one that had a slipping tranny and a Chrysler interior, one that had three gears, a 350SDL that burned oil (bad, bad, bad sign on a 350), one that was getting a rebuilt tranny installed and the guy never called me back.. I also found a bunch of gas powered ones that were great fun but also got 14mpg. Hell, it took me a while to find a decent W123, I also looked at a bunch of beat up cars, including one that wouldn't accelerate.. luckily I bought the first W124 I found without really looking for one and it's been an amazing car though not a diesel.

Thanks for the tip on the vacuum leaks, I've yet to look for them but good lord, it makes it a pain to drive as-is.
 

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You probably know this, but it's worth repeating: locate the manual engine "kill" lever and remember where it is. In fact, practice using it so you know what to expect. If your vacuum system goes nutty, the engine won't STOP running without your intervening with this manual kill. Be sure your wife or other drivers know about it, too.

Those cars are tanks, witness my teenaged nephew who, sure enough, got his W123 diesel T-boned one afternoon while attempting to cross a highway: the other car, moving at highway speeds, was totaled (as was his), and he walked away unscathed.

Good luck and enjoy!

Chuck
 

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Ha, I used to work for a Mercedes dealership.. we had a 1982/3 orange 300DT that wouldn't turn off unless you pushed the kill lever. That was quite an experience.
 

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I think the W123 is finally starting to come into its own, as a classic Benz.

My favourites are the TE's with the petrol twin-cam.

Still cheap as chips for the quality. A lot of car for the money.
 

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By TE, do you mean gas-powered station wagons? If so, I don't know if we got those. I'm no expert on these but I think the only gasser the U.S. got was the 280E.
 

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Yeah, the TEs were the station wagons. I am pretty sure that they came with Diesel engines in some markets, but here in Australia we only got the petrol (gas) engines. And they were lovely twin cam 2.8s moe often than not.

"E" denotes "einspritzung" or injection, so I guess the TE's were all petrol now that I think about it...
 

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I have been contemplating getting one, a diesel. They're very solid I think, and probably inexpensive....what's the going rate in the US??
 

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We were offered the gas powered wagons here too, but the diesels were the big sellers.

RDG, even though your kind of mean to me, I'll tell you more of what I learned from my diesels. The stuff I remember, anyway.

Make sure your vacuum pump is healthy. There are two designs, and one of the designs, when it fails, can scatter bits and pieces into the cranckcase. They are fairly easy to take apart for rebuilds.

A lot of the owners are convinced that a little Marvel Mystery Oil is good for the injection pump and the injectors, lubricates and cleans, just pour some right into the fuel tank. I had a few people tell me to put ATF into the fuel, because it also lubricates and cleans. I remember one old timer said he would put a quart of ATF into every tank of fuel. The helpful members of the Deisel Discussion Board, however, told me that ATF is not designed to be burned in a combustion chamber, and leaves harmful deposits.

When I replaced the front shocks on the SD, I didn't have to lift it or take the wheels off, I just turned the wheel all the way. That is, to replace the front left shock, I turned the steering wheel all the way to the left, reached in, in front of the tire, unbolted the shock, popped it out and popped in the new one. That was an easy day. Might be the same on the 123.

On a cold day, it doesn't do the motor any good to try to let it warm up by idling in the driveway. Diesels just don't produce enough heat without load. Even though it's slow as hell when it's cold, get in it and drive it. You just have to be patient.

Speaking of patience, you have to get used to how slow the car can be when you need to pull out into traffic, or cross a busy intersection. You learn to predict the future a little. It teaches you a mental discipline I like to call "dynamic preponderance". Fortunately, you have lots of heavy steel around you at these times.

IIRC, the 123, 126 and 140 chassis from Mercedes were the last to be engineered without regard to production costs. The engineering and material choices were not based on market influences. Back then Mercedes had the luxury to be able to say "Let's build the car right, then price it accordingly, people who can afford it will buy it". The result is some very solid, beautifully built cars. Quality materials make a big difference in longevity for a car, and I guess that's why you see a relatively large number of these twenty plus year old cars on the road.

I used Shell Rotella for oil. I very rarely used cetane booster in the fuel. I was commuting when I was driving my deisels, so they got highways miles all the time, which is what they are best for. If you spend a lot of time in town, cold starts and short trips, cetane booster may be helpful in the winter. Also, if your in town mostly, you may find yourself with a weak battery occasionally, even if your charging circuit is good. There is a lot of demand from glow plugs, the big starter, and the heater fan. Be ready with a charger.

Hope this helps.
 

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Discussion Starter #11
RDG, even though your kind of mean to me, I'll tell you more of what I learned from my diesels. The stuff I remember, anyway.
I know, I know.. I was rather harsh and I apologized. And I do appreciate you posting this.

Speaking of patience, you have to get used to how slow the car can be when you need to pull out into traffic, or cross a busy intersection. You learn to predict the future a little. It teaches you a mental discipline I like to call "dynamic preponderance". Fortunately, you have lots of heavy steel around you at these times.
And mine is a non turbo, just a standard diesel. The worst is if you get stopped on a steep hill.

IIRC, the 123, 126 and 140 chassis from Mercedes were the last to be engineered without regard to production costs.
Actually, it was the 124, not the 140. The 140s are usually mediocre cars. The only diesel available was the notorious 3.5 rodbender that got carried over from the 350SDL. The 124s are great cars, I can say that from experience :D

If you spend a lot of time in town, cold starts and short trips, cetane booster may be helpful in the winter. Also, if your in town mostly, you may find yourself with a weak battery
I've noticed that, never knew why though, I thought I had a drain on it somewhere.. thanks. In hindsight a drain wouldn't really make sense.

Do/did you have a block heater for yours? It wasn't supposed to get as cold as it did last night so I didn't plug mine in and try as it may, it wouldn't start yesterday morning. Eventually started after about an hour of being plugged in.
 

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Mine would start just fine, with no heater, down into the mid-twenties, Fahrenheit, which is about as cold as it gets here in Hot Springs. You need a motor with good compression, good glow plugs, and a starter in good shape. Sometimes, depending on your car's unique personality, it's helpful to "cycle" the glow plug circuit twice before cranking it over.

Even a motor with good comp won’t start if the starter can’t turn it fast enough. If your starter is more than five or six years old, take it out and get it rebuilt at a place that has a good rep. They will clean up the armature and put in new brushes, new bushings, you’ll get the most spin and the least battery drain. It's not much money, and well worth it. In my experience it's always better to have a rebuild done at a good shop than to get an over-the-counter rebuilt from a parts store.

There are a lot of diesel motors out there, and a lot of shops ready to deliver the intimate, caring, sometimes embarrasing, therapy needed by some of the bits of your old Mercedes. Look in the yellow pages under "diesel".
 

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Discussion Starter #13
Looking at the maintenance records for mine, I don't see the glow plugs anywhere which leads me to believe that they're old as hell. It starts up fine with the block heater though. I'll replace them if it becomes any harder to start but it's okay for now.

If you don't mind me asking, why did you quit driving the SD? I really like the way those drive.

Oh, bytheway, they had a W123 on Top Gear (along with a Beta, a 60s Opel Kadett and a Beetle-- all driving through Africa). Very interesting and entertaining, you can probably find it on YouTube.

I'm hopefully going to look at a 240D today, I may trade my 300D for it.. getting kind of tired of the sloppy automatic.
 

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It's surprising how well the 126's handle, I suppose because it's the same chassis that gets the big V8s for the Autobahn. On good tires you can really throw them around.

On the freeway on my way to Dallas once, I was puttering along in the slow lane when a tractor, in the fast lane, forgot I was beside him and came on over. His right front wheel had sex with my left rear wheel for about half a mile. I had a guard rail to the right of me, so had no choice but to keep pushing back until he finally realized I was there. The Mercedes stood it's ground.

Still the turbo SD, which weighs more and has the same engine, gets better highway mileage than the turbo 300D, I think it's because of the length.
 
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