Reliability of 85+ 300SD
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From: New York, NY
06 SV650S, 11 Santa Fe
Reliability of 85+ 300SD
A friend of mine was asking me how reliable this car is. One with around 150K miles to use as a daily driver. I told him I don't know much about the older diesels but I'd look around. From a basic search it looks like people are having problems with the ignition coils. Anything to look out for in particular? Thanks for your help.
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From: Kansas City, MO, USA
1989 560SEL, 1999 S600, 2005 S600, 2008 S550 4Matic
If the car was well maintained during its life so far, it should have excellent reliability. That car has a bullet proof engine. There will be no issues with the engine. However there are other parts of the car that are troublesome around this time given the age of the car. Things like the vacuum lines which control the automatic climate control, engine, power door locks, etc start wearing and breaking, etc. But these aren't major issues. If properly maintained, the engine and transmission should last for many more years and many thousands of miles more. At 150K miles, that engine hasn't even broken in!!
Ignition coils? Where did you read about that? That's not a common problem on the W126s. Especially with the kind of mileage on that car your friend is interested in -- if the miles are true and actual.
Ignition coils? Where did you read about that? That's not a common problem on the W126s. Especially with the kind of mileage on that car your friend is interested in -- if the miles are true and actual.
Last edited by braverichard; Feb 11, 2005 at 01:49 AM.
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Ignition coils are not a problem.
The 300SD has a diesel engine. No ignition system at all. Another way of looking at is that ignition coils last forever on this car. 
I have an '85 300SD with about 200k miles on it and the engine is in great shape. But nearly all of the systems that Braverichard mentioned need attention. The previous owner of my car did not fix many problems as they arose. My AC, climate control vacuum system, vacuum operated door locks, etc. all need troubleshooting. Maintenance by the previous owner is the key. If he changed the oil and filters religiously and fixed problems as they arose, then mileage is not an important factor because many of the parts that periodically wear out will have been replaced anyway.
From what I have read, 150k is about borderline for potential future transmission work. That would be a possible large future expense.
My impression so far, after a couple of months with my car, is that it will be an economical, long-term vehicle (barring catastrophic failures) for a shade tree mechanic. If you pay someone to do your car maintenance for you, it may be harder to justify from an economic standpoint.
RayG
I have an '85 300SD with about 200k miles on it and the engine is in great shape. But nearly all of the systems that Braverichard mentioned need attention. The previous owner of my car did not fix many problems as they arose. My AC, climate control vacuum system, vacuum operated door locks, etc. all need troubleshooting. Maintenance by the previous owner is the key. If he changed the oil and filters religiously and fixed problems as they arose, then mileage is not an important factor because many of the parts that periodically wear out will have been replaced anyway.
From what I have read, 150k is about borderline for potential future transmission work. That would be a possible large future expense.
My impression so far, after a couple of months with my car, is that it will be an economical, long-term vehicle (barring catastrophic failures) for a shade tree mechanic. If you pay someone to do your car maintenance for you, it may be harder to justify from an economic standpoint.
RayG
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From: Kansas City, MO, USA
1989 560SEL, 1999 S600, 2005 S600, 2008 S550 4Matic
Actually RayG,
I was wondering the same thing. Ignition coils??
Even on the MB gassers they aren't a common issue.
The key to owning one of these old but reliable cars economically is knowing well about them. I've been too busy or lazy to perform certain repairs/maintenance on mine many times and have had to pay someone to perform them, but still without going bankrupt. The key is knowing well enough about the car that when something happens, you're confident enough to order your own parts and go to a trusted mechanic and say "this is what I want you to do... nothing more, nothing less" and be 99.99% correct. That's my case. Most of the work that I don't do is done exactly as I say and I've never been wrong so far. You have to know the car very well or else you can be talked into changing parts that are perfectly fine. I've been told silly things like that the timing chain must be changed every 100K miles along with the water pump when I know a 300SD with its original chain at 322K miles! I've also been told that the injectors need to be changed every 100K miles, that the shocks need frequent changes, etc. If I didn't know enough about the car I could have been cheated. Also, these cars are so simple to work on that you can convince your MB-scared backyard mechanic to work on it for you without much effort.
I was wondering the same thing. Ignition coils??
Even on the MB gassers they aren't a common issue.The key to owning one of these old but reliable cars economically is knowing well about them. I've been too busy or lazy to perform certain repairs/maintenance on mine many times and have had to pay someone to perform them, but still without going bankrupt. The key is knowing well enough about the car that when something happens, you're confident enough to order your own parts and go to a trusted mechanic and say "this is what I want you to do... nothing more, nothing less" and be 99.99% correct. That's my case. Most of the work that I don't do is done exactly as I say and I've never been wrong so far. You have to know the car very well or else you can be talked into changing parts that are perfectly fine. I've been told silly things like that the timing chain must be changed every 100K miles along with the water pump when I know a 300SD with its original chain at 322K miles! I've also been told that the injectors need to be changed every 100K miles, that the shocks need frequent changes, etc. If I didn't know enough about the car I could have been cheated. Also, these cars are so simple to work on that you can convince your MB-scared backyard mechanic to work on it for you without much effort.
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Joined: Aug 2004
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From: Milford, CT
1987 300SDL aka the "Money Pit"
If you think a 300SD has an ignition coil then you need to have two things going for you to own one:
1. A good mechanic that knows them and can keep it running.
2. Not being afraid of paying that mechanic $3k-$5k a year to keep said W126 going.
Sorry these are old cars you really should be a diy'er or know something about these cars at least. If not ownership just is not pratical. Try a newer W210 or another newer car insted.
1. A good mechanic that knows them and can keep it running.
2. Not being afraid of paying that mechanic $3k-$5k a year to keep said W126 going.
Sorry these are old cars you really should be a diy'er or know something about these cars at least. If not ownership just is not pratical. Try a newer W210 or another newer car insted.
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Joined: Mar 2004
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From: Kansas City, MO, USA
1989 560SEL, 1999 S600, 2005 S600, 2008 S550 4Matic
Hey take it easy on the guy Hattie. I just finished changing the spark plugs, spark plug wires, distributor rotor and cap on my 300SD. Runs much better now. 
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Joined: Aug 2004
Posts: 240
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From: Milford, CT
1987 300SDL aka the "Money Pit"
Yeah my diesel runs so much better now with Bosch Plat 4's and a new K&N. I may even bring it to Jiffy Lube to get the oil changed. 
But according to the ebay sellers these cars all go 500k miles will little maintaince so I may just skip the oil change because I wouldn't want it not to make 500k!
I'm not trying to be hard on the guy just trying to help him avoid getting burnt on an old car.
But according to the ebay sellers these cars all go 500k miles will little maintaince so I may just skip the oil change because I wouldn't want it not to make 500k!
I'm not trying to be hard on the guy just trying to help him avoid getting burnt on an old car.
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From: middle of shit - saudi arabia
560SEL
a good maintained diesel benz is a very faithful car.. good maintainence doesnt mean to be dealer maintained but some professional mechanic should be incharge of the car..as well as consumeables replaced religiously on time.. the diesel engine will outsmart many gasoline counter parts in reliability and longevity!!
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Thread Starter
MBWorld Fanatic!
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From: New York, NY
06 SV650S, 11 Santa Fe
Thanks for the help. I wasn't really thinking when I typed that. The issues I had seen people talking about were with the glow plugs but all I could remember when I was writing my post was that it was an ignition problem. I'm not looking at buying the car, a friend of mine is. And he is definitely a DIY kind of guy so he'd have no problems doing basic maintenance by himself.
Thread Starter
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From: New York, NY
06 SV650S, 11 Santa Fe
He has to get it now. We killed his jeep over the weekend. We managed to burn through 6 quarts of oil in 400 miles on the highway. Every time we'd stop smoke would billow out from under the hood. So he's decided its time for a new vehicle.
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Joined: Aug 2004
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From: Milford, CT
1987 300SDL aka the "Money Pit"
I was being sarcastic. Actually back about 50+ or so years ago some diesels in tractors for example would start on gas and then switch to diesel or some sort of junk oil.
