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Mercedes 300D Suggestions



  • amonra22amonra22 Posts: 11
    One more thing I forgot to add to my posting, the brakes feel spongy and have to push to the floor to stop.I did bleed the brakes but only the front two that I changed. I was told that I probably need to bleed all four lines and that there may be a specific order that I have to do the bleeding in. Was wondering if that may be the cause of the sponginess, and if there is a certain order I have to bleed in. Thanks so much....
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 56,434
    It's possible you might have let in a little air yes. It's a good idea on these old diesels to flush out the brake system completely and have fresh fluid. Usually you bleed from the wheel furthest away from the master cylinder and then the next closer, etc. (this is for old cars, not new ones with ABS).

    Sponginess is usually an air problem. If you can't get the air out, you may have to bleed the fittings in the master cylinder as well. If that doesn't work you may need to have them "power-bled" at a shop.

    Did you put on new rotors? If your rotors are worn (even if they are relatively smooth) you may be pushing your luck. On your car, you don't turn the rotors when they wear to minimum thickness, you replace them (not too expensive).

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  • isellhondasisellhondas Issaquah WashingtonPosts: 19,392
    What am I missing? I assume you mean on the back of the pad and not the friction material? I sure hope so!

    Why would you do that anyway? to reduce squeaking?

    And I don't think you need to put grease on a spindle either unless there is something about those cars I don't know?
  • amonra22amonra22 Posts: 11
    thanks for your help. i did put on new rotors with the pads. thinking bout having it power bleed at a shop but it costs almost as much as the new pads and rotors. Also have a transmission question. Shifts into 3rd rough and kind of lurchingly, when it does there is some exhaust. Took it to Aamco, and the mechanic said it was fine that that is how a diesel shifts. Was glad to hear it at first but now not so sure I believe he knew what he was talking about. Had the transmission fluid changed any ideas as to cause or should I take it to get 2nd opinion.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 56,434
    Oh yeah that ZF transmission is a notoriously rough shifter. I love to watch 300d owner's heads snap back and forth when I'm behind them. On some models (but I don't think yours) you can adjust the vacuum modulator that controls shifting, to soften it, but I believe that's only on mid 80s on up. Sorry I'm not sure about this but there's too much to remember on Benz---they are always changing everything.

    You can try to bleed the brakes yourself using the old brake fluid in a bottle method. That works pretty well. You could even make your own power bleeder. I've done that. I drill a small hole in the plastic top of the master cylinder reservoir and insert very tightly some clear tubing (like for fishtanks) and then hook the other end to a can of compressed air (or you could even use a bicycle pump). The clear hose has to be tight, though. Then, with the brake fluid under pressure, I can do each wheel one at a time. Of course you might have to re-pressurize if you have to add fluid to the reservoir. then when I'm done I just plug the hole I made with silicon or wax or something like that. Be sure not to drill into the plastic cap's little air hole or if you do, be sure to leave that open when you seal the cap back up.

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  • amonra22amonra22 Posts: 11
    thank you so much. as this is my "run around car" and not my everyday car i have an 05 toruareg the rough shifting is something normal and I will get used to it. trying to have some fun learning to fix my mercedes. thanks for the help.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 56,434
    It's better if you shift manually. That helps some.

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  • Curious here..... car for car, everything being somewhat equal, would you rather have a used Mercedes, or a used Lexus? And why?
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 56,434
    Well Lexus doesn't make a diesel so the comparison wouldn't be fair---also the 300D was pretty much extinct before Lexus came out in 1990.

    You might wish to ask this question over in the Sedans topic, where they compare gasoline cars.

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  • HI all,
    I think my oil pressure is a bit low. Its above 45 when driving or accelerating or when it is still cold. After it warms and im in traffic or something its right around 30. When i get off the highway after 10-20 miles at about 70mph it is right around 22 or 23 ish. It just seems a little low but i could be wrong. Any feedback would be great. thanks
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 56,434
    normal! Oil pressure at low idle is an irrelevant bit of information as long as it picks up the instant you hit the accelerator pedal.

    Your oil pressure should "peg" when starting up cold. If you started cold and only got 22 psi, that would be worrisome. But warm? No problem.

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  • My dad has given me his old mercedes, it's a 1982 300TD with 300 000 km...

    all seems to be in working order, but it won't shut off, so after reading this forum, I am pretty sure the problem is a broken/leaking vacuum line, but has anyone ever had the vacuum pump itself fail?

    Also... is this car worth my time and money with all of the mileage on it? It is in awsome shape, in and out, but it has been off the road for 7 years... so i'm not really sure about it.

    Any help would be greatly appreciated!
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 56,434
    Sure the vacuum pump can fail. Do the door locks work at all? Those are also vacuum operated. You can rebuild the vacuum pump.

    Well if you've been off the road for 7 years you're going to have to clean out the fuel tank I think, change all the filters, get new tires, and certainly flush the brake system, radiator coolant, and replace the belts and hoses. So you might have to spend a couple hundred dollars to see if this car has any life left in it. 300km isn't too bad if the car was well taken care of, but 7 years of inaction are going to take their toll of course.

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  • dyates773dyates773 Posts: 24
    Update!! It's alive! The turbo is now operational. Here's what was done:

    1) Waste gate was stuck.
    2) 3 vacuum lines at the turbo were cracked, broken, or missing
    3) The intake mainfold pressure line to the vacuum control switch was missing.
    4) The Over-Boost Switch was totally plugged with carbon and the electrical contacts were badly corroded.
    5) All rubber vacuum line connectors were cracked and deteriorated.
    6) The air cleaner filter element was plugged badly.

    The test drive was incredible. It does not seem like the same car. The boost really kicks in at 2400 RPM and feels steady from that point on.
    Driving upgrade it was like a different engine, good steady power.

    It took a couple days but was worth it, on to the A/C problems!!!
  • Well i have an update... i put a new battery in my mentioned car, and with the turn of the key it fired up, a little smoke at first, but then it ran fine!

    Dad was telling me that when he first started having problems with the car shutting off, he couldn't find the problem, so he switched the hose for the locks, to the shutoff hose, and that worked fine for a while, but then that stopped working to... the power locks do not work. I am still thinking that it is probably the hoses. Would you by chance have any access to some type of vacuum line diagram, so I can see what needs to go where, and which hoses to check?

    I am going to just use some additives for the fuel tank for now, change the filters after some of that has went through, and I have to change the engine oil, tranny oil, and i will flush the coolant system. If the brakes work... do I have to flush them?

    It will need new brakes, and tires... for sure... but other then that... all seems to be well... ha ha... "other then that" :P

    Thanks for your help!
  • djocksdjocks Posts: 124
    Board, I know this is for the 300 D but I am looking for some help.

    I have the opportunity to get into a family owned 1989 300 SE with 71K miles on it and in very good condition for very little money. I was looking at leasing TL's and Bimmers but this sounds interesting.

    The help I am looking for is, Am I getting myself into a money pit? What type of MPG can I expect? how is the ride, how is the stereo? and how satisfied are present owners?

    Thanks, for the help...

  • dyates773dyates773 Posts: 24
    Just some general observations about owning any Mercedes. From a mechanical standpoint they are extremely well built. Most ordinary parts like starters, alternators, radiators, etc. are readily available at decent prices.

    In my opinion, having owned a total of 5 Mercedes is they can be a money pit when they get old. My daughter's '86 190E had a fuel injection problem that cost more to repair than the car was worth. All of the M/B's I've owned have all had A/C control system failures both electronic and vacuum. That's over and above the typical leaks associated with all cars. My '87 30SDL is in the shop today.

    I own them because they have a classic look, I enjoy restoring older vehicles, and my first car was a rusty beatup 240D that lasted forever.

    Oh I forgot, the sound systems sucked but I've never owned a 1993 or newer.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 56,434
    Yes, you MUST flush the brake fluid. You'll be sorry if you don't.

    Vacuum line diagram:

    You might try over at; otherwise, if he can't help you (he knows a lot) you'll have to buy the factory shop manuals (set of 3) which are well worth the money if you really like these cars and like working on them. They aren't cheap but after your first home repair you've paid for them easily.

    RE; BENZES in general. Old rule of thumb: "whatever got you into that used Benz cheap will eat you for breakfast sooner or later".

    So buy the best used Benz you can afford. Don't buy a project car, you can't win...if you're in it for fun, then great, it's not such a problem and you're doing a lot yourself, but sometimes it is much much easier to spend more money up front and get a really well cared for Benz. Only the very skillful and clever and patient should buy a "fixer upper".

    Stay away from 190Es, that was not a great model.

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  • amonra22amonra22 Posts: 11
    have an 82 300D turbo, was driving to work this am and felt some surging at normal frwy speeds when I was driving. My car then began to loose speed on hills and then on normal flat roads. All the fluids and filters have been changed and was wondering if anyone might have suggestions as to the cause. My top speed was around 45-50 mph after the surging started. No smoke or loss of oil pressure or busted hoses, and other than the surging and loss of power no other symptoms I can list. Any help would be great. Thanks.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 56,434
    Sounds like bad injectors maybe? You should also put in a strong additive to try and clean them. Also check your turbo tubing for any loose connections or leakage, and finally, check for a sticking or malfunctioning turbo wastegate. If your wastegate is dumping boost randomly, this could account for your symptoms, as could a very irregular spray pattern on the injectors. I'd really have to drive it to tell you the differet feel of these two deficiences.

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  • amonra22amonra22 Posts: 11
    Have used a fuel additive in my last 2 tanks of diesel. Changed the fuel filter and lines could some of my problem be waste from the fuel tank clogging the fuel lines, and I should replace my fuel filters again? How often do you recommend fuel filter replacement? If my wastegate is malfunctioning or sticking how can I tell? The surge in power is very slight not like the turbo is kicking in like you are pushing the gas peddle and then letting up on it quickly. Could you recommend an injector cleaner? Thanks.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 56,434
    Yes, BGK44 is a good injector cleaner. A bit expensive but it works.

    Other possibilities? Maybe your cruise control is kicking in and out by itself? Perhaps you can disable it by pulling the fuse temporarily? Usually Mercedes cruise control on these cars conveniently disables itself, or runs amok, and often---it's quite unreliable. I'm just trying to think of different things it might be. Just pray your injection pump is okay. It's VERY rare for that to go out. I believe it is also adjustable (the pump) but this would require an expert who knows EXACTLY what he is doing.

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  • zero3kzero3k Posts: 6
    Okay, here's something new for all of you.. I only hope someone has an answer.

    I bought this car about 7 months ago, it's a 1984 300D European (Yes, it's gray market.. most things are written in german, it has a top-front filling radiator, and the three-dial system for the A/C. The car was apparently non-turbo when produced in Germany, but a turbocharger (and transmission) were later added. I checked, and sure enough, there was the old turbo.

    Now, the problems. I've owned an American 300D prior to this one, which had more problems than I ever wanted to deal with, so I ditched it for this one. The car isn't the fastest thing in the world, but I have to wonder if the turbo is even working at all. On the american one, it sounded fine.. the car would rev, shift, and the turbo would go *Pfsst*. Pretty fast little thing, too.. for a diesel. Fast forward to now, and instead of hissing when shifting, the turbo sounds like it's constantly purging. During acceleration, there is a constant hiss. It's probably the wastegate valve, like I've read on many topics.. but where is this valve located, and how do I unstick it?

    The only other major problems I have, is the A/C system. I turn the dials to cold (For the right and left sides of the car), close the middle vent slider, and turn the upper dial to 100 (for 100% through the compressor). As soon as I turn it off 0, I hear a relay under the dash click, but the engine won't even bother engaging the compressor. My guess, is that the system simply has no R-12 in it, and it just needs to be recharged. Probably leaks, too.. but that's for a later time. Also, there is a small rainwater leak in the rear right floorboard.. my guess, is that it comes in from the sunroof (This one has a manual sunroof with a tommy-lock.. which I personally like better than the clunky auto one I had). My question is.. how do I clean the sunroof drains?

    Thanks in advance for the help.. oh! And one more thing.. is there a way I can determine the engine model? Since this car differs so much from the American model (even has cloth seats), I want to make sure it's not just a 240D in disguise.. so where on the engine would the OM617 designation be? Thanks guys!
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 56,434
    It can't be a 240D as those are 4 cylinder cars.

    First thing you need to determine is your chassis this car a W123, W116 or W126? Then you'll know if it had a turbo from the factory or not.

    I can't imagine anyone would go through the hassle of adding a turbo to a non-turbo W123 but they could have installed an SD or SDL engine I suppose.

    I think you are correct about your diagnosis regarding the turbo and the AC problems.

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  • zero3kzero3k Posts: 6
    The chassis type is definately a W123.. I fell in love with that design ages ago, and haven't turned back, since. Like I said, the car is gray-market, so I honestly am not sure what they come with over there in Germany.

    Totally forgot that the 240 was only 4CYL.. whoops. The engine type is an OM617 (Engine says R-O617.9..something), so I'm pretty sure it's a 300D engine. Found it printed on the side of the engine, near the injection ports. Anybody else have one of these Euro models? A good deal of stuff on it, is pretty foriegn to me, compared to my old US model. For example, I can't find the upper valve for the A/C system (to charge / discharge). The lower valve seems to be on the compressor itself, and the upper? Who knows.

    Now, if I only knew what the wastegate valve looked like, where to find it, and how to fix it.. I'd be set! :)
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 56,434
    617 isn't necessarily just a 300D engine. It could be a turbo engine from another model. I'd have to look it up. They are all 617s but might have different numbers after the decimal. It would be better if it wasn't a stock 300D engine, they really weren't built for turbos, but probably would be okay with low boost. Most turbo engines are strengthened internally.

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  • amonra22amonra22 Posts: 11
    Have a 300D turbo, the fuel gauge reds full when u fill the tank. However when it starts to to read
    1/2 a tank and below it begins to jump wildly, 1/2..1/4...R. I was told to check the fuel level sensor it may need to be replaced. Its easy to find under the first aid kit but how do I tell if its bad and how do u remove it? Also the reserve light on the fuel gauge stays on all the time.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 56,434
    It does sound like the float or float switch, yes.

    I don't know any easy way to test it although I'm sure the answer is buried in the factory manuals, using an ohmeter or something. Since the symptoms are correct for a bad float level switch and since you've hauled the old one out of there, might as well take a chance and replace it.

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  • zero3kzero3k Posts: 6
    Recently had the "reserve light always on" problem. Swapped the fuel level sending unit out with a used one (a working used one), and the problem went away. Of course, using a used one wasn't a fix that'd last forever.. and my gauge started jumping around lately, too. Replaced with a brand new one (You can get it cheap from, and haven't had a problem, since.
  • fusefuse Posts: 3
    Those cars are great! I've got a 1976 300D that I run on 80% free waste oil I get from restaurants. The car is in awesome shape, but I've got the same problem: it won't shut off.
    I patched up the leaky exhaust system wwhen I bought it last year, and it shut off then. But I banged it up last month and now it won't shut off again. I presume it's a problem with inadequate back pressure due to a leaky exhaust, but I won't rule out an electrical problem (the curse of the 300D).

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