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  #1  
Old 10-23-2005, 06:38 PM
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I heard there's bad diesel engines years (85-87)? Is it true?

I love diesels...don't we all? Well, at a old mercedes shop a few months ago I asked the mechanics which years to buy or not buy and they said stay away from 85-87 or something like that. All before are great and all after are good they said.

Well, today I stopped at a mechanic shop (junkyard) looking for some parts and got talking to this old guy that seemed really knowedgeable about cars...I spotted this diesel mercedes in the yard and we got looking at it! It was an '87 300SDL. He said it was the best old benz you can get! It had a 6 cylinder turbo and I questioned him about bad years and he said this 87 6 cylinder was best.

Anyone got a suggestion what engines are the best old engines?

Are the 5cyl. engines better?

thanks for any help,

Caleb

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  #2  
Old 10-23-2005, 08:18 PM
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The early six cylinder engines with the #14 aluminum head are prone to cracking, especially if overheated. Later versions of this engine have increased stiffness to reduce the risk of a crack.

However, there are many forum members with these heads that have over 250K on the engine without problems.

The 617 has a cast iron head, but, it's not immune to cracking either. Don't ask how I know this.

The OM603 six cylinder engine is more fuel efficient, smoother, and much quieter than the five cylinder OM617.
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  #3  
Old 10-23-2005, 08:22 PM
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The 5 cyl :617, is considered to be the most reliable, they only made them unitl '85. Oh and the 4 cylinder version (240D's) are also in the same class...

The 6 cylinder: 603 is a total goddess but a bit more finicky. They are known to have some head cracking issues, as well as the later version's would bend a rod from time to time.(I believe that was a 3.5 litre version of the 603)

look through the archives with the search engine, you will find plenty of stories to keep you entertained and informed for hours.

good luck and happy reading
J
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  #4  
Old 10-23-2005, 08:31 PM
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You must have heard about the 350
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  #5  
Old 10-23-2005, 09:05 PM
BusyBenz
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With all due respect for the above response, and these guys do know what they are talking about, I'll add my 2 cents.....

What you heard isn't, and wasn't false, but I do believe those mechanics were telling you something, but only something they heard!

The people on this forum are better knowledges, I believe, and will tell you what is real as opposed to hear-say.

To be specific about the OM617, or OM603, or other variations of Mercedes-Benz diesel engines, you will hear truth positive, or first count, observations about these engines, bodies, full account, in this forum!

I have been a member of this forum for only less than two years and the wealth of knowledge here is short only by less than incredible! You are conversing with the brightest and best knowledges about Mercedes-Benz automobiles. Listen to what they say, and take their advantage of their experiences!
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  #6  
Old 10-23-2005, 09:16 PM
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The 603 is better! After driving the 300SD around for a couple of days I miss the machanical scream of a 603 at 5k rpm. The 617 sounds like a pissed of John Deer, not that it doesn't have its charms.

Other then a few 14 heads cracking you really can't go wrong buying any diesel in those model years. Drive both and buy whatever model you prefer.
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  #7  
Old 10-24-2005, 06:09 AM
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Caleb,

All in all, the engines are great but don't buy any diesel engines found in any S-Class sedans after 1987. Simple and straight forward.

To summarize it, the OM617 5 cylinder engine is great for someone that wants and engine that's tough as hell and pretty much bulletproof. However, that engine's roots date back to the 70s so it isn't high on the refinement scale. The OM603 six cylinder engine on the other hand as some issues here and there and requires more care than the 617, but is more powerful and much more refined. These are just S-Class engines. I believe all MB diesel engines made after 1986 had aluminum heads, and so they share the typical characteristics of the 603 (actually, until a certain year in the mid 1990s, all MB diesel engines from 1986 belonged to the OM603 family - someone correct me if I am wrong here).
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  #8  
Old 10-24-2005, 06:39 AM
Mark Tamburrino
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Thats close

602.911 (1986-89 190D 2.5)
602.961 (1987 190D Turbo)
I have never driven a sdL, so 5k rpm might seem o.k. with a 603, but that many revs in a 617 just seems wrong, like it is wearing out at a much higher rate. Not to hi-jack the thread, but there is a million dollar industry in the making of load banks. These burn electricity produced by industrial generators and are used mainly to make the diesel engine driving the generator work closer to its max power. By over-reving and under loading(generators can't really vary speed according to load-they stay at high revs) the diesel engine wears out faster. Glazed cylinder walls for one thing, I don't remember the rest. In summary, I like the 617 but the final drive ratio/ # of revs at highway speed has got to be changed. I believe it will not be overloaded if it did 1000rpm less at 70mph. Wonder if a 2.47 differential from a 126 would work in a 123 chassis, or five spd with o/d.

1984 300D 210k +/- Needs odo repair
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  #9  
Old 10-24-2005, 09:04 AM
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A 300SD at 5000 rpm would have a piston speed of 77000 fpm.
A 300SDL at 5000 rpm would have a piston speed of 70000 fpm.

A 300SDL has a stroke that is less than 91% of the OM617.

Thus, at 5450 rpm, the 603 piston speed would match that of an OM617 doing ~5K.

5K in an 603 is like 4550 in an OM617.
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Last edited by DslBnz; 10-24-2005 at 09:11 AM.
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  #10  
Old 10-24-2005, 09:19 AM
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Quote:
Originally Posted by DslBnz
A 300SD at 5000 rpm would have a piston speed of 77000 fpm.
A 300SDL at 5000 rpm would have a piston speed of 70000 fpm.

A 300SDL has a stroke that is less than 91% of the OM617.

Thus, at 5450 rpm, the 603 piston speed would match that of an OM617 doing ~5K.

5K in an 603 is like 4550 in an OM617.
You are comparing piston speed vs. rpm's.

If you were to compare forces vs. rpm's the comparison would be more significant. The forces involved with accelerating the piston are proportional to the square of the speed.
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  #11  
Old 10-24-2005, 10:10 AM
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Wow, there is really some experience on this forum! Thank you for the replies and info!

Brian Carlton,
I notice you have both engine types...so as a first time Mercedes buyer, which type should I get? I have read about the extra expense of the 603 motor! It is too much for a first time MB owner?

I currently drive diesel rabbit's and have driven an '83 300D, but this 300sdl in this junkyard looks so sweet! It is black and has a recent paint job! The guy said he used to race his cop friends with it! He said it does an easy 100 on the highway and has had it to 140mph! Anyways it has sat for 8 years and has just 130,000 origianal miles on it. I'm not sure he ready to sell it yet, but he's coming around...I told him to let me know when he's ready to let her go! (I think I can persuade him, he liked my interest in it)

I guess I will have to look for the engine # and see if it was a later built engine.

Anyways, I love tinkering with cars and have done all my own work on my rabbit(no engine teardown yet) and don't mind doing all I can to keep 'em running! I just don't want to be 4 grand into a car purchase and then need lots of expensive parts.

Any idea what average price per year to drive an old MB is? Not purchase, but upkeep and repair?

Thanks y'all! This forum is great!

Caleb
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  #12  
Old 10-24-2005, 10:21 AM
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Quote:
Originally Posted by PagodaLover
You must have heard about the 350
YES! the 350's are the hottest and sexiest!
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  #13  
Old 10-24-2005, 10:23 AM
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Quote:
Originally Posted by DslBnz
A 300SD at 5000 rpm would have a piston speed of 77000 fpm.
A 300SDL at 5000 rpm would have a piston speed of 70000 fpm.

A 300SDL has a stroke that is less than 91% of the OM617.

Thus, at 5450 rpm, the 603 piston speed would match that of an OM617 doing ~5K.

5K in an 603 is like 4550 in an OM617.

My 3.5 will not spin beyond 4200 (dash tach).
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  #14  
Old 10-24-2005, 10:34 AM
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Quote:
Originally Posted by andmoon
YES! the 350's are the hottest and sexiest!



Many a man has been led to his ruin by a hot and sexy thing.
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  #15  
Old 10-24-2005, 10:34 AM
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Quote:
Originally Posted by mrbisset
Brian Carlton,
I notice you have both engine types...so as a first time Mercedes buyer, which type should I get? I have read about the extra expense of the 603 motor! It is too much for a first time MB owner?
Oh, I suppose that I should advise you to buy the older and simpler 617 engine otherwise I'll be crucificed on here.

But, in reality, the 603 is a fine engine. It's more sophisticated but it's quite expensive if you need to go inside it for any reason.

The final determination should be based on condition. If the vehicle is in good shape and had maintenance records, I wouldn't dismiss a 603 for a first time M/B owner.

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