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Mercedes 300D Suggestions



  • I'd check the fluid and if it's at the right level I'd do a major service anyway on the transmission; other than that, you'll have to tear it down and investigate I think. Noises inside a transmission are not a good sign, nor is slippage of any kind.
  • My recent transmission shifting problem was solved by cleaning the valves inside the transmission and adjusting shift points. Be sure to take it to someone who knows about MBs; ideally someone who does only MBs.
  • Well anyone who works on German automatics should be okay. Grinding noise isn't a good sign though as a sticking valve body might not cause something that noticeable.
  • tijolotijolo Posts: 9
    what are some tests that I can do to check to see if my '78 300d is in need of a rebuild? Its only got 84k miles but....its burning more oil then I would expect. Constant blue smoke and burning 3.5 quarts in 2,000 miles. Half the 2,000 miles are highway miles but that seems like a lot of oil to me.
    The engine seems to be running fine, its usual sluggish self. I have changed all the filters and fluids and ran a couple of rounds of injector cleaner.
    Any suggestions would help. thanks
  • cylinder leakdown test will reveal all.
  • heypeteheypete Posts: 2
    This is in reference to

    I have emailed the seller for more information, but have yet to hear back from him. Hopefully I can see the car, subject it to my extensive battery of tests (much of it gleaned from reading this thread), test-drive it, ask a ton of questions, and if everything looks good, take it to a trusted Mercedes mechanic I know to do a full inspection on it.

    According to the pictures and the (albeit brief) description, the car looks to be in good condition. Seller wants $4,300, which is a bit high. Blue Book private transfer is about $1,200. I'd probably make an initial offer around that, and haggle.

    The only potential problem I see from here is mileage: The car has 248k miles on the odometer. Status of service records is unknown, but will be asked about. I'll definitely ask to see them. I will, of course, consult with the mechanic to examine the vehicle before I'd purchase it. I'd like to get (hopefully this isn't unrealistic) at least 150k more miles out of it before having to do major work on it. I'm fairly mechanically adept, but unfamiliar with Mercedes internals...I do, however, know a few people who are rather familiar with them, and who would help me out with any hands-on work I need to do. I'd prefer to do as much work as possible myself to avoid high service costs.

    One interesting bonus: the car has been modified to run on vegetable oil, and comes with the filtering/fueling station as part of the purchase price. Depending on the quality of the station, it might be worth an extra thousand dollars, maybe more or less. The fact that the engine is pre-converted to biodiesel is a plus too, as I was hoping to do that eventually.

    Assuming I can get the car and station for $2k-$3k, and that it is cosmetically and mechanically sound, does this sound like a good deal? I realize I'm asking for an opinion on a vehicle that you have not yet inspected, and with a fairly small amount of information, and I'll take those givens into account.

  • aloha sam! this is a delayed reply to you, but thank you very much for your thorough explanation of transmission variables. i have found a 84 300d that shifts "firmly" and no slippage. (and she's gold and beautiful on a more superficial note). thank you very much for your advice,
  • aloha! i just bought a nice 84 300D with no apparent issues except.....
    after driving a couple or less minutes there occurs a whistling/squealing sound ONLY at one certain point on the pedal, the sound reappears also at this same point when decelerating. it does not matter what speed i am going, nor uphill/downhill. i haven't noticed it starting immediately upon driving, so i might venture that it doesn't happen at very low speeds.

    i reiterate: the sound is connected to very specific spot when pressing/easing the gas pedal both accelerating/decelerating. beyond that one point there are no funny sounds whatsoever and performance is fantastic

    all belts are in good shape. no leakage. no temperature issues.
    (i can't check mpg because odomoeter is broken, but it seems to be pretty damn good). i can't inspect the engine while the sound is occuring because it only occurs while driving. (unless you have some suggestions for how to?).

    my initial thought was turbocharger issues but i have limited understanding of this, so i don't understand why it would happen relevant to gas pedal and not specific speed nor gear? bearings seem unlikely since there is no sound at higher/lower speeds, increased/decreased acceleration. maybe it's not the TC and there's some linkage in the fuel system that would create such a sound? fuel pump? i just don't get it..... do any of you???

    thank you!!!!!!! (by the way, i am very happy to join all you in the ranks of MB diesel fans, this is the best car i've ever driven! it took me awhile to find her but i'm so happy i didn't settle for a subaru! biodiesel coming soon!)
  • any tips on replacing the instrument panel light and/or adjustment knob on a 84 300D, depending which one is faulty, without removing the steering wheel etc? i'm just figuring out this car, are there secret back entrances? has anyone ever just pulled out the knob and re-threaded it? i'm sketched out by little plastic breakable things.

  • 300d300d Posts: 6
    Mr shifty HELP!!!! please

    I have a 1985 300D, that and the hazards only work when they are in the mood to. I put on a new combo switch, all new fuses and a new relay. but nothing has changed. Whats next? should i go thru the harness? run a new wire? is their something in the system that i don't know about? or should i move to the front lawn and plant flower in it?
  • If I recall, I think the entire instrument panel just pries out along the rubber seal. I can't recall how good the access is when you do that. The little bulbs are twisties and they often corrode at the contacts and this is why they stop working. Very typical problem. You can buy all this stuff at the Benz dealer, they stock it.
  • Why are the hazards such a big deal for you if I may ask?

    Anyway, do your directionals all work?
  • 300d300d Posts: 6
    um i realy don't care about the hazards. how ever driving with no turn signals it is pretty hazardous. so to answer you question the turn signals do not work. when the ocation pops up were the hazards work the lights will blink at least in the back.
    I think i have a blown bulb in the front. but i haven't changed it because im buying knew fender and i want to do every thing at once.
  • Well all the bulbs have to be good for things to work properly. You might loosen the bottom part of the steering post so you can access the directional signal switch and perhaps that black coupler is loose or you'll see some disconnect in there. You can also take a simple test light and see if there is current to the various sockets in the front and rear bulbs. Also a bad ground at the bulb sockets will cause this, so get in there and clean and jiggle things around.
  • Thanks for your messages. I think the problem started after driving on a very bad and dusty road. That road really was completly covered with powder, at least 1 foot of dust... I noticed that the problem started after that day, may it be the cause? How can a road full of dust damage the transmission? Thanks again.
  • I don't think the road conditions are related.
  • goldcargoldcar Posts: 23
    I have talked to that seller before. They regularly purchase old Mercedes diesels, convert them to vegetable oil then sell them with the fuel station. The car is probably already sold at or very near the price advertised. On the plus side, they do get every car well looked over before the purchase it for the conversion, as they don't want to get stuck with a lemon after investing all the time and money into it.

    I ended up buying a cheaper and unconverted '82 300D after I realized my lifestyle just would support another hobby like collecting vegetable oil. Now, if someone were selling vegetable oil ready to pump into my tank for $1 per gallon, I would be all for it.

    If you are not planning to "do the vegetable oil thing", then skip that car and get one unconverted.
  • Hi, I am new to the forum. I really enjoy reading the postings as I have managed to apply a lot of the suggestions posted here to keep my 1983 300 D in shape. I bought the car 5 years ago due to nostalgia as it reminded me my childhood trips in taxis with my father in Europe. Then I also realized that is a marvel of engineering.

    I am having a similar problem with my turn signals. They do not work all the time. They only way to get them back is if I turn the hazard switch on and of a 2-3 times. Any suggestions?


    Thank you
  • goldcargoldcar Posts: 23
    I fixed the door locks on my 1983 300D a few months ago (replaced front passenger door lock actuator) and thought I had mastered the vacuum system. Hah! A couple of weeks ago the door locks stopped working again and engine shut-off took 20 seconds. I used my vacuum pump/gauge to determine the interior locking system still worked.

    In the engine compartment I found the lines running into the interior (air conditioning and door locks). If I applied vacuum pressure to it I could operate the door locks fine and it held a vacuum. The line to it came out of what I guess to be a one-way valve (white).

    I then connected my gauge on that line going back into the main system (leaving the interior sub-system disconnected). Then I disconnected the second line going to the central vacuum connector and plugged it with a gold tee. I re-started the car and pressure shot up to 20-22. I turned the key off, but the car kept running of course as the shut-off valve was part of the second sub-system I disconnected. After pressing the STOP button (darn useful thing), the pressure dropped to 0 over the course of 30 seconds or so. Meanwhile, there was a ticking sound while the pressure dropped.

    The hoses looked fine, but there could certainly be a problem with them that I don't see/hear. My main problem is that I don't know how this system should work. I am thinking that maybe it is ok that the pressure drops in the main system, but then there should be a one-way lock sealing off the door lock system. Is there one?

    But then, the pressure should be a bit higher or constant to get the fuel shut-off valve to work faster.

    Is this a problem with the vacuum pump problem? The brakes feel fine.

    HELP! Advice most appreciated. Is this something that is covered in the $100 factory manuals? (If so, I am happy to get them.)

  • heypeteheypete Posts: 2
    Hmm. All right.

    I actually did a bit more looking around, and I found a 1992 300D turbodiesel in surprisingly good condition. See the pictures here. No more pictures, as the camera battery was low.

    Body was in great condition other than a few mild scuffs on the back bumper (as noted in the last photo). Engine started promptly and ran smoothly. Transmission shifted smoothly between gears at both city and highway speeds. Suspension felt really good.

    Interior is in excellent condition, with no visible wear on anything except a small crack on the wood veneer next to the ignition (looks like someone missed the keyhole and poked the wood with the tip of the key). Doesn't look like anyone ever sat in the back seats. No wear on the leather at all, it seems. Very minor wear on the rubber on the pedals, suggesting a minimal amount of stop-and-go driving.

    Car has 198k miles, and the seller reports that it's nearly all highway miles. He's the second owner, and has kept the car garaged all of the time it's not moving -- he bought it with the intention of shipping it to Uruguay where he spends several months out of the year, but the taxes and fees for that were too much, so he kept it here and rarely drove it. He only put 3k miles on it since he bought it 4 years ago. Previous owner was a woman, and evidently drove it regularly on the freeway, but very little in the city. Maybe she was a saleswoman or something?

    Seller wants $8,500, which is about twice the Edmunds TMV. I may be willing to go a bit above the TMV if my mechanic examines it and determines it's in very good running condition and no major work will need to be done other than regular service for the indefinite future.

    I'd be trading in my two-year-old Honda Insight (2003) with 20,400 miles on it for the Benz, and would like to make sure I'd be making a good impression. One of my diesel-savvy friends says that it's not uncommon for Mercedes-Benz turbodiesels to last upwards of 400k miles with proper maintenance. The Insight is a bodywork-hog, requiring expensive bodywork even for minor things like rock impacts. Even with slightly higher maintenance and service costs for the Mercedes, I think I'd save money in the long run.

    Any advice?

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