Hi folks! I hope you all had an excellent Christmas!
I'm a newbie to this group and I'm wondering if any of you have, or might
know of one, a 123 series, 5 cylinder, 3 litre diesel Mercedes (with the
chrome bumpers) that might be available to buy. I'm looking for one and
understand that Mercedes ceased making these around 1985. If any of you can
offer some information on these seemingly rare cars, I would be most
Many thanks indeed.
Happy New Year!
I have an '84 300D so I take notice of other 300D's on the road and
there are plenty of them! For a start, check eBay to get an idea of
what they are going for, but be aware that the diesel engines only last
around 250,000 miles, perhaps to 300,000 or better if they have been
Well, I guess there is a lot of unacceptability with 300D engines. How
many mercedes diesels have you seen that made to 500,000 miles without
internal engine work? Mine lasted 260,000 miles before it lost enough
compression to make it hard to start, this is about average from what I
hear from the experts.
George Mann wrote:
Well, my unacceptable non-turbo 1980 300CD engine only made it to 208,000
before the timing chain broke. I've put another 60,000 miles on that engine
since the rebuild. In all fairness, the cylinder walls were not all that worn
when I took the motor apart. I went to the first oversized piston which is
0.25 mm oversized and the crankshaft journals were like new. But I have a
1985 300D with approximately 200,000 miles on it and it still does not burn oil
between oil changes. And then I have a friend who drove his 1979 240D to nealy
400,000 miles without any engine work before he sold it. So who really knows
how long those engines last?
All of [-m,my 300's have made it beyond 500K. They were all original
617's as fitted in the W115's.
In all my years of owning and servicing MB diesels, I have only seen
three types of failures within 300K.
One is damage to a motor from excessive lack of oil changes (fairly
Another is running out of oil, usually do to a hole in the oil pan
To continue my involitarily aborted post...
The third is the result of broken timing belts.
The problem I see most often however is tight valves. This results in lost
compression, hard starting, and can eventually lead to a valve job do to
Please see my other post.
There are only 3 things that normally go bad on a diesel.
1. Valve seals.
3. Timing chain/tensioner.
The 3-litre 617's are bullit-proof! All of mine exceeded 500K with only the
rubber valve seals and timing chain having been replaced.
Timely oil changes and valve adjustments are the most critical factor in
the longevity of a motor.
Also, you will need to use a good fuel treatment/injection cleaner every 6-
When I rebuilt my engine at 260,000 miles I found that the intake valve
guides were worn out (sloppy!) while the exhaust guides were still good.
Valve springs were good. The clyinder walls showed very little wear, so
I replaced the intake guides, did a valve job w/ new seals, honed out
the clyinders and put new rings on the cleaned and inspected pistons.
Now I have all my compression back, it starts in freezing weather with
just the glow plugs, and doesn't smoke a bit-- cold or warmed up. The
timing chain had previously been replaced.
I'm not sure why the intake valve guides failed, I suspect that the EGR
dumping exhaust into the intake might have had something to do with it
*if* the intake guides were made of a softer material than the exhaust
guides. Had the intake guides held up better the intake valves would
have kept their seal with the seat better instead of dancing around and
losing compression. The exhaust valves had quite a bit of carbon built
up on them from the low compression. The engine used maybe half a quart
between 4,000 mile oil changes so the oil rings held up. Compression
(top) rings? I don't know if they were weak or not, but I replaced them
anyway as they would have shortly failed with the increased compression
after a valve job.
So, would this engine had lasted 500,000 miles with regular oil changes
and 15K valve adjustments?-- I have to say in this particular case, no.
George Mann wrote:
When I opened my 1980 617 engine after the timing chain snapped, I found cracks
in the cylinder head, worn exhaust valve stems, worn exhaust guides, lots of
polish on timing chain rollers and just a bit of cylinder wall taper. I was
the second owner of the car as I purchased it with 67,000 miles on it. The
original owner changed the oil every 5,000 - 8,000 miles. As far as I can
tell, the engine was never overheated yet the head developed cracks.
By the way, I have a friend with a 1981 300D and that engine uses a quart of
oil every 800 miles. Could that be bad valve seals or? I would like to think
the 617 engines are 500,000 mile engines but my non-turbo 617 didn't even come
close to your mark. Will my engine make it to 500,000 if I change the oil every
3,500 miles like I've done since the rebuild?
I've been using 15W - 40 Chevron Delo but according to Chevron it was the first
motor oil to make it over one million miles between rebuilds on Cummings, Cat
and the other large diesels. Chevron reformulated Delo oil a couple of years
ago so I'm too worried. Chevron claims that their Delo 15W - 40 rivals
synthetic oil in low engine wear. They also say that the synthetics only
exhibit advantages at very low temperatures. I believe both Delo and Shell
Rotella are made from type two base stock. And... I like Delo because it's
readily available at Costco.
I have always heard the "500,000 mile" ability of the diesel Mercedes engine,
but I can't think of the last one I have seen for sale or even one that someone
owns or has owned. The reality from what is written here and what I have seen
personally is that 300,000 miles is about the most you can expect, and thats
with the finest of care. And yes, I know there are the traveling salesmen or
taxi drivers who drive their cars 150,000 a year and can reach 500,000 mile
with little trouble, but that kind of mileage per year is NOT the norm.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.