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Mercedes 300D Suggestions



  • 1)Is the jolt produced by the rear end or the transmission? 2) a vacuum leak is highly suspect, however another avenue or two may be a) low trans fluid level; b) poor adjustment of the shift linkage; 3) possibly the adjustment on top of the rocker arm cover that controls the trans could be out of adjustment. This line is easy to adjust. Just pop it off , make sure the ball tht i ataches to is at its stop, then if needed , simply turn the adjusting screw ( it is white in color, probably made of nylon) turn it 1/2 turn clockwise, start car and drive it ablock or so; if there is an improvement in the shifting, leave it alone( make sure you drive fast enough to go thru all the forward gears before reaching your decision that is is now ok.. If no improvement, repeat process with another 1/2 turn clockwise. if no improvement, turn white knob back or counter clockwise to is original position or 1 full turn counterclockwise; thee repeat process by turning 1/2 turn counterclockwise, test drive again and see if there is improvement. Believe me it basically is a trial and error process, but with patience and perserverance you possible will be rewarded with success in this process. Have fun! :shades:
  • coach17coach17 Posts: 10
    edited December 2011
    I have a 1981 300d with 200,000 miles. The heat works fine at times. However,if I turn it off, then turn it back on a little later, it blows cold air. I have found that if I stop and turn car off then re-start it, the air will be hot again. (the heat seems to only work on high. And only comes out of defroster and upper vents, nothing out of the lower foot vents) My commute is about an hour. If I keep the heat on the whole way (glad it has a sun roof!!), the air will turn cool after about 45-50 minutes. Any suggestions???

    Thank you
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 63,862
    yeah, that sounds like the typical Benz problems with the climate control unit. There were two systems, the earlier one being the most notorious.

    Not sure which system you have, since your year is on the 'cusp', and also Mercedes at that time were often registered as 1980s when they were actually 79s, and as 81s when they were actually 80s (long story).


    It tells you which control unit you have at about 1:30 on the video. If you DO have the earlier control unit, you'd best watch the whole video. If you don't, then come back and we'll take it from there.

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  • Mr. Shiftright...I watched the video. I do not have that climate control system. My buttons run horizontal. Any suggestions?

    Thank you
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 63,862
    Well then you're in only have the* second* worst climate control :P I think you should investigate these people --

    I suspect that your problem is in these controls somewhere.

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  • Hello,

    Does anyone have the schematic for the vacuum lines on a 1981 300d transmission. I am told this is a California car and the # on tranny is 722.118.

    I have a 1981 300d with 200,000 miles. It seems to slip or flare from 2nd>3rd, and 3>4. 2nd>3rd seems a little worse. Also, it shifts into third at around 25MPH (which is very close to the 2nd>3rd shift around 20-23MPH). I can start out in "S" and then shift into "D" at 30 mph and it doesn't seem to slip.

    The tranny looks like it may have been taken out and possibly had work done. I'm hoping it is just a vacuum issue.

    Any suggestions???

    Thank you.
  • dotishdotish Posts: 20
    Quite honestly, if you're new to this car you may be experiencing the typical behavior of the 300D tranny, especially if you're trying to accelerate quickly.
    When I first got my 1980 300D I was alarmed thinking that I had a problem. After reading some posts here and talking to a few other owners in person, I realized that I was trying to push the car too hard and that I was going to have to relax and settle for slow acceleration since pushing it harder didn't speed things up, it just caused the weird shifting you're having. I don't think you have a problem.
    I'd see what others have to say, but this is my experience.
  • My blower motor would no longer turn by hand once removed, I also discovered that replacements are no longer made, and if you actually find one it's at least $168 online but NAPA did not have it in stock anymore.

    My successful $53 solution:
    Use a blower motor from a newer Chrysler and 'make it fit'. I went to an O'Reilly Auto store in Kansas City and Tom the Eagle Scout helped me out. The motor that Tom found is the VDO PM3324 for $53. The motor diameter of the body and the shaft are an exact match. Electrically it works perfectly at all speeds from ultra low to high, and this solution does not require any modifications to your original Mercedes wiring. However the new motor is constructed a little different and some creative engineering is required to get the fit just right.

    Before you start
    Use a voltage meter to verify the blower motor electrical plug has 12 volts when you turn the ignition key on. A no fan issue could be a resistor or fuse problem.

    Tools required:
    Bench grinder, basic metric socket set, screw drivers, crimping tool, 3m black vinyl tape, 3m double sided foam tape, hammer, drill with 15/64th bit or so, one male one female red spade connectors to crimp to the motor wiring, semi rusty vice grips optional.

    First remove the old motor under the passenger dash, so remove the panel first. The electrical connection easily pulls straight down. If you remove the 4 machine screws from rear to front, it will fall right into your hand, if like my 15 year old son you remove screws front to rear it will fall right onto your head. I love teaching my children the finer points of working on cars :shades:

    Remove the single bolt in the middle that holds the motor in place. The motor can now be wrestled out. Note the 4 vertical ridges in the Mercedes plastic that holds the motor.

    The new motor bottom needs 4 notches:
    The VDO motor has an ridge in it's bottom cap construction, I used my bench grinding
    wheel to notch this cap flush with the body in 4 90 degree cuts to fit the plastic ridges, 2 of them at the 2 attachment bolts on bottom, the other 2 90 degrees from these bolts. I recommend making them a little wider than required for an easier fit, a tight tolerance won't help you here.

    The new motor needs it's bottom cap circumference reduced:
    The bottom cap has a outside ridge, carefully rotate the motor against your bench grinder to reduce, but not remove, the outer lip. Once it fits into the top of the Mercedes plastic base this task is complete.

    Protect your wiring!
    The black and blue wires come from the top of the motor. Cut the foam tape, stick the wires below this so they are flush with the side of the motor. Wrap with 4 or so times with a good 3m black electrical tape. I highly recommend you avoid the cheap stuff here!

    Drill the New mounting Holes:
    Getting the new motor into the old Mercedes plastic requires a firm tapping, not hammering. Place on motor on your work surface, with shaft just off to the side and tap the plastic on the motor. When the bottom two mounting bolts hit bottom the will leave your drill location marks. Wrestle the motor out and use a 15/64 drill bit to make 2 new holes. Hint: remove the extra two nuts at this time. Re-tap the plastic onto the motor making sure the bolts come through the holes, attach with the washers and nuts that come with the motor.

    Cut no wires, Make the Electrical Connection:
    The fan requires a CCW rotation when looking down at the top of the shaft. Terminate the black wire with a red(22-18 gauge) male spade to fit into the Mercedes side female connecter, which is the + voltage side. Terminate motor's blue wire with a red female spade connecter for ground. The motor wires were a very tight fit into the red connectors and crimped down just fine. I did not cut any wires, and was able to nicely tuck them both down into the plastic base when done.

    The smart choice, a new squirrel cage:
    The shaft is a little longer, this was not the problem as there is room above. The original motor top is tapered, and the original fan support is curved to match. The new motor has a right angle top, not tapered which means the original squirrel cage fan cannot be tapped down as low on the new motor. Though this is not what I did I think it's likely the better choice.

    Plan B, What I did:
    Tap the old fan onto the shaft, when it reaches flush, use a deep socket to tap it further down about 1/4 inch, until the motor top is just barely not touching fan. I actually had the slightest of fan to motor rubs, as I assumed it rubbed itself out during the first 20 minutes of operation.

    The new system will be about 5mm to tall and the an will rub on the top side. I used a blue foam 10mm thick and 4 screws that were a little longer that the original and it works great. Photobucket Photobucket

    The foam I cut into a circle around the bottom of the fan, and use a marker to trace and cut the external plastic shape. A couple small pieces of 3m double sided foam tape and
  • watexwatex Posts: 3
    I recently purchased an 84 300d with 49k miles. It had been living in a dry climate (LA) and stored for several years. The car runs great and performed perfectly during the journey from LA to Seattle.

    The paint (gold) is showing evidence of wear (small scratches) on the sides of the body. Roof, hood and trunk are okay. I would like to have the car repainted. I took it to a paint shop recommended by my local MB dealer here in Seattle. They told me the clear coat was cracking and could not be repaired. They recommended a repaint. The prices quotes were incredible ($7k if I keep the same color and $12k for changing the color).

    I have several questions:
    1. What is a good price for a repaint job (using MB colors)?
    2. Should I keep the same color (I do have a preference for another MB color that was available that year)?
    3. Is replacing the seals (around the doors and trunk lid) a big ($$$) expense and is it something that I could do (not being a weekend mechanic yet).

    Just getting started with this car. It is the first classic car I have purchased. I actually owned a similar car new (back in 84) so am reliving my past!

    Any guidance and recommendations would be helpful.

  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 63,862
    Well I think it would be a good idea to drive this car for a while before investing in paintwork, just to make sure all the usual 300d bugs are out of it.

    The door seals are a good idea and no problem except that you have to be very neat about the application of the glue--so if you aren't somewhat fastidious, and have good glue solvents on hand, you might farm this out. But it's hardly rocket science.

    Good paintwork is very expensive because it is a) intensely labor dependent work and b) if you don't use the best paint materials, the job won't last.

    To give you an idea of the range of quality, I have spend more on the PAINT and MATERIALS for a paint job, without even opening the cans up, then what Miracle Auto Body charges to paint an entire car.

    That's a lot of money to invest in an old 300d and you'll never see it returned on resale, so unless it looks really awful you might think about living with it, at least for a while until you see how the car works out.

    Pay particular attention to the heater/AC system controls, to the rear hydraulic compensator, the front coil springs (they sag). Invest in good brakes and tires, and perhaps a water trap for your fuel system. Get used to using additives for the fuel (biocides, cetane enhancers, injector cleaners), and change the oil frequently. Flush out the coolant, too if the old stuff is still in there.

    Good sturdy old car, though!

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  • watexwatex Posts: 3
    Thanks for the input. I think you are right. The finish looks okay from about five feet away. I may try some elbow grease and buff as much as I can.

    I noticed that the trim (aluminum?) is dull (faded) and not shiny. Can I buff the trim (e.g. around the windows) so that they return to their original shiny state? Is there a product that brings the condition back?
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 63,862
    yes you can buff it out--but be gentle. Start off with that very fine bronze wool that they use to buff out the fittings on sailboats and powerboats. AND BE SURE to stay away from the paint---mask the paint off if you are going to use bronze or very fine steel wool.

    On restoration work on very expensive cars, they often remove the old trim, and carefully tap out the dents with a tiny hammer (you have to really know what you're doing in this case) and then buff the trim on a wheel, using a very fine jeweler's rouge. But that's probably too extreme for your situation.

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  • watexwatex Posts: 3
    Thanks so much for the guidance. I guess I have my winter projects lined up!
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 63,862
    Just remember that ALL polishes are *abrasive*, no matter what the gentle, gentle, is the word on an old car's chrome and paint.

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  • lydia2lydia2 Posts: 18
    Read the info online here. I have not had anything done like Steveo did. I do not drive this Collector too much. I noticed that the gas guage is fluttering. You speak about grounding a possible problem; so how do I investigate this? However, as the battery has run down a few times, it has had a charger on it to bring it back. The battery has been checked, is holding its charge and I try to drive it to keep it that way now.

    Do not want this problem or anymore like it; please suggest my solutions.
  • lydia2lydia2 Posts: 18
    Guess I conveniently forgot that my odometer has not worked for last ten years or so and that the tac comes on periodically for a duration of 5-10 minutes occasionally. I did a few $$trips to the mechanic who wanted to look for something electrical. Too expensive and no results, so I have lived with those malfunctions. Mr. Shiftright solved my turning signal problem, much thanx!

    Any chances of help with this business?
  • reugenioreugenio Posts: 2
    The door latch does not latch completely into the door striker. One mechanic looked at it and recommended changing the door striker but problem not solved. Another mechanic(Mercedes Benz) inspected it and said the problem was the latch itself,but the part is very hard to find.Also suggested to look up auto salvage parts.Also suggested to look for a right front passenger side latch.disassemble it..maybe the problem on the left side is only a spring inside? What would be the best way to resolve this and make the door work latch correctedly? Where do you find this latch?
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 63,862
    I bet you could actually order that latch from's worth a'd be amazed at the number of old parts you can still order from them.

    Barring that you can try here:

    Also, breezing through the "Mercedes parts" section of Hemmings Motor News (

    these door panels come off pretty easily, so if you're handy I agree with your mechanic--take the lock out and see if its just a busted spring.

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  • I've been looking at old mb's and thinking about taking the plunge, but now I've found one that's really in the deep end. It's an 83 300 turbo diesel, but it hasn't been driven for over 10 years. I'm told the filters have been changed, and it runs, but not much more info, other than 'everything works'. Mileage is said to be under 120k. I'm virtually blinded by the red flags waving around but can't help wondering if it could be returned to driving condition, and at what cost? Exposure has done a number on the paint but there's apparently no rust - dry climate here, so this could be true, maybe. I'm not too worried about cosmetics as much as viability. Turn and run, or proceed with caution?
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 63,862
    Depends on the price of course, and on what works and what doesn't. Some red flags would be a) hard to start----diesels should start right up without cranking very much; b) inoperative heater/AC controls. That can get pricey; c) lots of black smoke that does not dissipate after the engine warms up d) excessive turbo whine (like a police siren).

    These are very good cars but the mythology surrounding them has to be taken with a dose of realism.

    Not running for 10 years is not a good sign--the tires will be no good, and one wonders about the condition of the fuel tank.

    Best thing i could say is don't buy it unless you can drive it around and give it a good test; otherwise, if you have to buy it "as is", buy it as a parts car.

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  • TO WAGONLUST: The name wagonlust perhaps suggests they are looking at a
    TDE. these can be rare in certain instances, and perhaps this is a barnfind. At any rate I concur with Mr Shiftright, however to add to that, if you are willing to take the 'leap of faith' and can afford the risk, go ahead and leap. It may turn out to be the best leap you ever took. :shades:
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 63,862
    A wagon would be worth more of a risk, up to a point. I just saw a pretty nice one (not perfect but very presentable) sell for $7,500---ready and running.

    You have to start with "good bones"--you can't build up a good Mercedes diesel if you are starting on a rotten foundation.

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  • fintailfintail Posts: 46,946
    One positive...IIRC, 83 is considered a very good year for 123s.
  • oops - it's an 81, not an 83, same diff, right? It does seem to be good bones but the seller is too enamored w/ 'low miles, collectible classic' to let it go cheap so it'll probably fall through. I'm thinking 1.5 max but they want over 4. I can't see paying that much if it's not been driven for so long and has lousy paint. Am I wrong? Thanks for the thoughts.
  • fintailfintail Posts: 46,946
    4 is definitely too much if it won't clean up with a good detail. Neat kind of special interest cars, but a ways to go before 123s become real classics. Make sure the turbo works, too. I am sure 81 is fine, but generally, the newer the model in a series, the better.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 63,862
    edited April 2013
    it's not a classic and the miles are only "low" relative to how old it is. Miles are still miles, wear is still wear, and 120K isn't "low miles" for all the parts of a car. $1500 sounds like more than enough for what seems to be just a roll of the dice. The car has too many unknowns.

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  • tdetempletdetemple Posts: 2
    My A/C works fairly well in the morning, as the day warms up it doesn't seem to work so well.
    Any advice???
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 63,862
    Well of course check to see that it is fully charged; you might also make sure the electric cooling fan is working properly once the car warms up, and that the condenser up front is not totally clogged up with dirt/bugs/etc.

    These AC systems are marginal at best so if the car is new to you and you are in a very hot climate, you have to be realistic as to what the system can do for you.

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  • tdetempletdetemple Posts: 2
    I have had it charged, I do see some bubbles in the viewer glass.
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