How big a money pit is a 300d?

Pedalsteel

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I have an 03 tdi wagon I love and have been eyeing 300d's but I'm wondering just how big a money pit is your average 300d in decent driving condition? The one I'm looking at currently (1983) has hardly any blowby and drives well without lags and slurs in the shifting...virtually no rust odometer still works...am I looking at replacing every part in addition to going from 52mpg to like 22mpg constantly looking at ways to increase mpg in this expensive diesel market or am I worrying too much? Thank you
 

Mongler98

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Incoming life story. TLDR: take care of it and a few grand every few years or every 100k (whatever comes first) is about right. Payoff is good


If it was not kept up with, it will eventually cost thousands all at once.
a good rule of thumb on most all cars worth under 5 grand is to keep things around 2 grand every 2 or 3 years or basically 80k to 100k miles.
If you see yourself spending more than that then you might want to go to a different car.
Scangauge II and some lessons on driving good will yield the best band for the buck. Tune and nozzles are next. Everything else takes 5 to 6 years in fuel offset costs to pay off in difference vs the one or less years for what I listed above.
2 grand includes tires and glass as well as maintenance.
Most every car I have owned all falls into the category of 2 grand every 2 years of around 60k to 80k. This includes 3 fords, 2 Chevy’s, 1 Boxster, 1 cayenne, a Daihatsu, a 71 Buick, and some a rare Honda accord that cost nothing to drive for 5 years. If you can do better than this great.
OH btw the Jetta was the most costly car I have ever owned.
VW are money hogs vs nearly anything else in its class.
My current fleet is a 01 dodge Cummins, the cayenne 955, 05 Boxster, 98 Toyota wagon, a 03 eurovan, an escape with 312k miles. This is between my entire families I do service for. they all have a service record going back to nearly new miles, and they all have about the same miles save for the escape, about 95k to 120k and the eurovan is the #1 most costly to maintain, by twice the cost. The cayenne is the least costly to maintain.
The MK3 I had I put 180k on it and I spend exactly 6,490 in maintenance and tires for the entire daily driving it got. At end of life I got 30k on all the performance stuff and junked it. The TDI was almost 3rd in line, the dodge is 2nd most costly. The Honda accord I got for $300 and sold for 500 and did oil changes and tire scams though Walmart and never cost me must of anything.

That also is DIY level and NOT paying someone for labor.
IMO if you have to pay a mechanic to do your work, do not buy an old car, it would be cheaper to spend 15k to 20k in the long run.

Rust is the #1 thing you have to keep on top of. That and TB and oil changes. Keep fresh fluids and filters on it and don’t go crazy with mods and she should give you a very good payback but its in the savings of fuel, not cost of maintenance as they are generally more than most cars in its class (30mpg honda accord from the same decade)
 
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Mozambiquer

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Scangauge ii, tune and timing belt will do no good on a 300d...
They're an old school mechanical diesel that are reliable and last well. They're not powerful or exceptionally economical, but they are a good car.
I've only seen a few issues, mainly worn linkages, oil leaks and I saw one with a broken cam, but that also isn't common.
 

Mongler98

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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
Sorry I was fixated on his 2003.
Yea I have no idea on those older mechanical TDIs.
The $ over time and miles still generally applies.
I think my old 71 skylark is proof of that.
 

Pedalsteel

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I do my own repairs...I love the Mercedes way of doing things even though I have never owned one... I've read thru a bunch of posts and material to get what their thing is, at least in the w123 days and for the most part w124...I don't find the vw to be all that costly... I'm at a stage in the mileage where a few things need addressed but it's a good car... way more comfortable than the civic I used to have... I'm done with Japanese cars...I like the non computerized aspect of the w123 and to be able to fix it when it needs it...the 22mpg figure I threw out there it turns out is more like 20 according to the current owner... I'm thinking it needs a new timing chain, drip timed, compete fluid and filter change, and valve adjustment... but will I gain any significant mpg bc that's where the rubber hits the road?...oil cap dance test it doesn't even move so that's a good thing...sounds great... probably needs diesel purge to go with the other stuff...outside of a rear end swap which I've heard is relatively easy, what will be the best consistent mpg for 60/40 highway use? I usually go 70mph tops bc the cops just bust you anyway around here and they won't if you go 70 and it's an easy cruise...is 30mpg unreachable with that gearing? The thing is my mom had heart surgery last year and when i told her I was going to get another diesel as a backup and for people hauling to and from the Dr appointments (i have 3 elderly to do this for and might be at the same time lol), she really leaned into an older 300d as a suggestion...i. just don't want to be dropping a ton like I bought pandoras box...
 

Andyinchville1

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For max cheap running hard to beat an old idi ( or di) mechanical diesel and black diesel :-0.

I thought about an old diesel Mercedes also... ( Even if nothing more than to convert another vehicle to diesel relatively cheaply).

Even if it needs fixing old stuff is far cheaper than the new high tech stuff ... I was surprised at some of the price differences in parts.

From description sounds good and if reasonably priced I'd go for it...

I'm still waiting on my centrifuge... They are all way back ordered due to parts.

Andrew
 
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rocky raccoon

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I sold my 1983 300CD about two years ago. It brought enough money to pay cash for my present 2014 VW Jetta Sportwagen TDI. I had that car for 8 years and spent many enjoyable hours under the hood. It is far more easily repairable than the TDI and parts are readily available and reasonably priced. Build quality far exceeds anything from VW. It had 360000 miles when I sold it and the buyer came from New York City for it and drove it home.

Bottom line is; I wish I still had it.
 

Tom in PT

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I've often thought of adding a MB W123 diesel to my fleet but so far haven't found the right one. The fuel economy of the 300D is just not very good at least compared to a modern diesel, and mid - upper 20s is what I have seen from my research; 30 mpg would probably only happen under ideal conditions at 50-55 mph. The pluses are build quality, reliability, indefinitely maintainable, easy to work on, and available parts, lots of support in the MB community (and from mercedessource and their videos). I would recommend to Pedalsteel to get a prepurchase inspection - a lot of things to look at and consider before making a purchase decision. By the way, Kent Bergsma from mercedessource recently listed a 1983 240D with manual transmission that he had done a full mechanical restore on and was asking ~$ 24K for it and the ad went down quick.

My understanding is that the later W124 diesels (rather rare) from 86-87 have a more powerful engine, better fuel economy and more safety features and you might expand your search for one of these editions of the 300D.

After giving up a search 5 years ago for a good W123 or W126 MB (including gas and diesels, all the ones I looked at had major problems) I ended up buying a really really nice 2005 Lexus LS430 and am very glad I made that decision. Awesome build quality, rock solid reliability (at 136K miles now), low maintenance costs, and the fuel economy believe it or not is about what a 300D would get me: 23 mpg overall over the last 10,000 miles and 27-30 mpg on the open road at 55-70+. The LS430 will long outlive my 2013 VW which has less than half the number of miles on it as of today.
 
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Pedalsteel

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Tom in PT that's pretty much what I've figured... the w124 from 90-93 is a good mix of features, ride and mpg with the aluminum head being the issue... if you look at one of these, check out the coolant tank bc when the head gasket starts to go, the tank looks like someone has run tobacco smoke thru it instead of it being that yellow/clear color...and the other issue with the w124 is the ac is a PITA to fix and expensive to take to a shop... most of the current w124 diesels I'm finding on marketplace have both of these issues and the asking price is too high for what the cars are... I'm watching them sit for months unsold...the rear gearing of the 85 rear differential and of certainlater model gas cars can give better mpg with a swap which is what I'm possibly looking at doing, I've read it's not really that difficult but finding a car that doesn't need just about everything is hard... they are 37+ years old... I'd like to pull the trigger and make it work for my mom to get her kicks in as she has always liked them but my dad being a diehard Ford guy and overall Mercedes hater lol, for real, wouldn't get one and instead they had a Lincoln...Kent Bergsma is the man btw his videos are a great source and his teaching style is also good
 

oilhammer

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There are just too many to list....
This was one of the MBs I had:



The old ones were really solid, overbuilt cars. Sturdy and long lasting. That car was just shy of $40k new in 1984... so it was not cheap, and I would not say it would be cheap to maintain although no major things broke on it. They do have a lot of quirks.

At this stage, I would think of it more as a hobby car. I sold mine to buy my 2004 Passat [new]. I don't regret it, as the Passat has served as well for 18 years and 250k miles, and continues to do so.

The W126 though, for a big sled of a car, was surprisingly nimble to drive. They handle far better than you'd think (light years better than any domestic sedan of the era), stop better, steer better, and once you got used to driving it and keeping it on boost (sort of like riding a wave on a surf board), it was not at all bad to drive. A little delay off the line, but predictable. The climate control was kluge and kinda lame, with parts sourced from GM and whomever. Those old iron engines had a different kind of sound, too, and while reasonably quiet inside they were noisy outside.
 

oilhammer

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There are just too many to list....
It may have been able to almost tag 30 if driven slowly, but mid-20s was more realistic. It was no TDI.
 

Pedalsteel

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Ever have the 2.5 turbo w124? I'm close to pulling the trigger on one of those with around 150k no rust needs tires and clear on roof is shot but really clean...I go back and forth on which one to buy if I do... mostly this is for my mom who has been in and out of the hospital so she can vicariously own it thru me riding to her appointments but I want to put some miles on it... I'm just afraid it will be like pandoras box with every rubber part on the car needing replacement one after the next...
 

IndigoBlueWagon

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I had a W124 2.5 for 8 years, sold it last Summer. It was a lovely car, but in truth I didn't drive it much. What oilhammer says about these cars is true, and they truly are built like bricks, and fairly easy to work on. Fortunately I never had any problems with the vacuum system, which is fairly complex and runs EVERYTHING: Door locks, HVAC, even the transmission shifting.


Back in the 80s I had a Peugeot 505D, and the M-B reminded me of a better version of that car. I still love old Pugs, but I can't imagine what it would take to find parts for one of those.
 

Pedalsteel

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So you didn't have any of the biodegradable wiring issues that plague the w124? Or did you have one that had the wiring harnesses replaced? I think every Mercedes should come with a mityvac lol
 

IndigoBlueWagon

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None of those problems. The wiring is pretty simple on this car compared to the gasoline powered W124s, and temps in the engine bay are much cooler. This engine was simple enough that it still had the shut off lever on the injection pump in case you needed it because shutting the car down was, of course, also controlled by vacuum.
 

oilhammer

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There are just too many to list....
I grew up around MB products, as my grandparents had them. At one time they had three W115s, all gassers, a '68 250 sedan, a '70 250 coupe, and a '72 250 sedan. When my grandfather retired, the '68 ended up going to an uncle, the '70 was sold to a family friend, and the '72 got traded on a new '79 W123 300D, their first diesel. Then that got traded on an '85 300D, their first TURBO diesel, and my grandfather being handicapped had a difficult time modulating the accelerator. So you could get a bit "seasick" riding with him (grandma drove most of the time, thankfully). Then that got traded for a W124 300D 2.5 turbo in '89. Then that got traded for their last car, a 1996 W210 E300D (which was back to a non-turbo engine, oddly enough). That car, sadly, had a few problems... which was more than any of their previous cars. Neither W123 ever broke, although they didn't have them long they did drive them back and forth from Missouri to Florida quite a bit. The W124 had a couple minor things, but nothing major... but that W210 was by comparison a piece of junk. And my grandma really loved that car, because it had a return to that more elegant rounded classic MB look. It was a wonderful driving car, was very refined and quiet, and it had no issues moving itself despite not being turbocharged. But it had a lot of QC problems. Door electrics, strange pops and noises in the suspension, random dead batteries, all kinds of annoying stuff. The engine/transmission were fine, but the rest of the car was just problematic.

I'd say the W124 was a quantum leap forward from the older cars in terms of style and refinement. That was the first diesel they had that you really didn't know it was a diesel from inside the car... and the W210 was no more noisy than a gas engine (they had nice sound coverings underneath).
 

Pedalsteel

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What would you offer a 92 300d 2.5L with no apparent issues minus needing tires and headliner sag 150k? No rust coolant resovoir is clear with no signs of carbon stain...
 

IndigoBlueWagon

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Any rust? Look around the jack points. Everything works? Cosmetic condition? My '93 had single stage paint so no issues with clear coat failing.
 

Pedalsteel

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No rust even around the jack points...headliner pretty bad sag in the rear...clear coat on roof is going bad but the rest of the car is good very clean no real dents interior very clean seats no rips everything works starts quickly guy is pretty cool open to questions
 

Pedalsteel

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I'm waiting to see pics of thermostat sensors for bio wiring or if that has been changed but he says he is aware of those gremlins and hasn't had any of them
 

IndigoBlueWagon

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Clear coat failing to me indicated it's been repainted. Prices are crazy these days, but $6-8K if it's a really nice example? I'm guessing.
 

Tom in PT

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I looked at and drove a couple of early 90s W124 diesels (one a 2.5L and another a six cyl IIRC) and did not like it at all. The NVH was just bad and they seemed slow and unresponsive. A completely different and unacceptable driving experience coming after 20 years in a VW tdi. Not to mention the rust, oil leaks, etc.
 

oilhammer

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There are just too many to list....
Something must've been wrong with them. The turbo OM605 moves the 124 just fine, and despite being about 1000 pounds heavier than the ALH cars (not to mention they were ALL automatics) it holds its own with those, too.
 

IndigoBlueWagon

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I've driven W124s with dead turbos or big boost leaks, they're not great. If the ALDA system is working properly even one in good shape is slow off the line compared to a manual TDI, but once it gets rolling they move right along. Remember you've got a 3600+ lb. car with 119 HP. What surprised me is despite that low power the 300D would happily hold 80 MPH with 4 people in the car. Little known fact: That boxy looking car had the lowest drag coefficient of any sedan during its production run. Really helps at highway speeds.

Gearing matters too. In that era Mercedes used pretty short gearing on all their cars, diesel and gas. 75 MPH in the 300D was right at 3000 RPM.
 

Pedalsteel

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Well someone got to it before I did(logistics and schedules didn't line up)... guy was cool during the process though which gives me hope bc it's a jungle out there cruising marketplace and searchtempest for a decent car... I'm currently debating the w123 vs w126...I tend to like the older w123 and w126 more anyways except the mpg...oilhammer did you happen upon your w126 or did you seek it out over the w123 body style? someone needs to make a kit that essentially turns these into a diesel hybrid kind of like a locomotive or to make an affordable device like a gearvendors unit... not sure how it would work but I ponder that quite a bit...i. think the one fuel (charged batteries) future the powers that be are trying to convince us is a good idea is just the opposite... there is literally a land mass the size of TX floating in the pacific that could be melted down into fuel and touted as an environmental victory...I think where I am headed is either a w123 or 126 and looking to eek as much mpg out of it as I can or.to start making my own biodiesel from as pure an oil source as I can get...I do live in the Midwest and there are soybeans grown here
 

rocky raccoon

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Pedal, my W123 (300CD) got a reliable 26 to 28mpg. That wasn't too far from my 2008 E320 that has the V6 Diesel. It sees 28 to 32mpg. The current JSW with it's CJAA regularly sees over 40mpg. I would still rather be driving the old Benz.
 

d24tdi

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I will second the suggestion that the W124 cars with the OM60x series engines were a big step forward. Especially the 6cyl versions. Holy grail of those is the 1987-only 300TDT wagon IIRC. As far as old style mechanical injected prechamber diesels go that OM603 is pretty well bulletproof and the W124 is a nice car and modern enough to be a good car to use daily. The turbo 603 engine had something like 140hp and could really move, plus very refined and also more efficient than the old 5cyl OM617 engines in the W123 cars.

Best I can remember, their only real downfalls were the trap oxidizer that needed to be removed from the exhaust, and some cars got a flawed cylinder head casting that liked to crack and needed to be replaced with the updated part. Probably most of the cars still on the road today have had that done by now.

Personally the W123 cars and the old OM616/7 engines never seemed worth the hype to me. The basic cars were solidly made, but little stuff always was going wrong.... oil cooler hoses, motor mounts, endless vacuum system issues, throttle linkage, driveshaft guibos, etc etc etc. Hard starting in the winter, or no start at all if you had even one or two glow plugs out. Climate systems were an endless PITA, power windows and their switches always were failing, etc. The 300Ds with more luxo features were worse for the interior part failures and climate issues, and automatic transmissions were common for causing trouble or failing. Poverty spec 240Ds with manual transmissions were simpler and had fewer problems in the interior and powertrain, less of a constant effort to keep those cars going. But the 240Ds were total dogs that got only 30mpg or so, pretty much unsafe on anything other than city driving or a dead flat highway, and even the turbo 300Ds were still heavy and slow and even less efficient, lucky to get low 20s for real world driving in the experience of our customers at the shop where we used to work on a lot of them. For the same size and age vehicle, a Volvo 740 turbodiesel with the VW D24T was more spacious, better built, much lighter and more nimble, much faster, quieter, smoother, cheaper to maintain, and about 5mpg more efficient. I never understood why people bought Mercedes instead of them. Same story with BMW's E28 524td available in the same era. Better in every single way. Have to figure folks were buying the MB cars over those others because they were the the bigger status statement at the time, and that's why there were so many more of them sold.

Contrary to the legend, we also saw a lot of those OM617 engines just simply wear out. Low compression. Many of them around 150k. They could last a long time for sure if strenuously maintained, but they weren't bulletproof, especially in the hands of owners who thought "bulletproof" meant "low maintenance". We saw timing chains stretch and break too, turbos fail, etc. The OM617 shared its design roots with Mercedes diesels going back to the 1950s or earlier, no joke. By the '80s they were antiques, to say nothing of today in 2022. 70-80 year old design principles, looked like something from the stone age when you had the valve cover off. Every other diesel on the market was more advanced, especially the lightweight VAG and BMW diesels. Fortunately the OM60x motors shared nothing with the old OM61x and brought them into the modern era finally.

I did like the W126 platform cars better than the W123, but the problem (IMHO) with those was that you could only get the short wheelbase "SD" models up until 1985, using the old OM617 5cyl engine. In 1986 they changed over to the new OM603, but you could only get it in the long wheelbase "SDL" body. Couldn't understand why they made that decision. That was just too much car for most uses, almost like a limo, although they still drove very well even with all the length and weight. The best combo would have been the short body with the late 6cyl engine but as far as I am aware, that was never available in the US.

I could imagine considering a nice W124 or W126 car with an excellent mainteinance history and no vacuum or climate system issues if one turned up. Still a costly to maintain and not-that-efficient vehicle with irritating problem areas, but nice enough to drive that it could be worth the effort to keep one going. But I don't think anything could convince me to live with a W123 or earlier.

The simple answer to OP's question -- yes they are money pits, all of them. If you're gonna buy one, spend the money upfront and get the absolute best one you can. The old saying goes something like, "there is nothing more expensive than a cheap Mercedes" and it's true.
 
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