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Old 09-24-2010, 12:48 PM
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Join Date: Sep 2010
Posts: 11
choices! '84 300sd or rebuilt '92 300d for wvo?

Hi everyone. I'm shopping for a diesel Mercedes for two tank waste veggie oil conversion and I was wondering what would be best. I know the older ones are great as long as you do it properly and change to hoses that can handle the bio fuel. My question is, which would you choose for this project? I'm looking at a 92 300d that cosmetically looks great and had the engine and trans. rebuilt 60k miles ago. This one sounds great and was leaning towards it but I noticed the 92-95 300sd is on the list of cars to avoid on another Mercedes forum. Do you think an 84 300sd with 250k miles on it would be a better candidate for WVO? Is the 84 significantly easier to work on? I'm looking for ease of conversion, ease of maintenance and reliability since it will be a daily driver. They are both the same price so which of these cars would you choose for the project as an amateur mechanic?
Thanks for any help!

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Old 09-24-2010, 12:55 PM
92 300D 2.5L OBK #59
Join Date: Feb 2007
Location: Central FL
Posts: 1,108
There is a difference between the SD and the D. The D is a W124 with an OM602 motor that is very reliable. The SD is known as a rod bender. Others are more knowledgeable then me in about that.

I'd go with the W124 with the OM602 engine.

Years to Avoid?
92 300D 2.5L OM602 OBK #59
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Old 09-24-2010, 12:56 PM
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Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,569
You mention 3 different cars...
is a 92ish SD in the choices (350L "RODBENDER" block)
or just a 92 300D 2.5Turbo?
either way, I'd stick with the pre86SD personally. the block can handle gook better, and you don't have the IP issues of the newer vehicles.
are you running WVO or Bio?
WVO does not need special fuel line, just heat. BIO does not need heat, just special fuel line...
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
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Old 09-24-2010, 03:03 PM
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Join Date: Sep 2010
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ah thanks a lot guys...My choices are between the 92 300D 2.5 turbo and the 84 300SD. I noticed the 92 SD on the list to avoid so i just wanted to mention that. Good to know it's not the same as the car I'm looking at. I'm going to run wvo, not biodiesel, so thanks for letting me know i dont need to upgrade my fuel lines. Like I said the 92 has a fairly fresh rebuild on the engine and trans and obviously just looks newer all around. So on one hand I have the 84, which I like the body style better and may handle the wvo (much?) better? and on the other hand I have the much fresher (cosmetically and mechanically) 92 300D 2.5 turbo. Any more thoughts?
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Old 09-24-2010, 03:06 PM
mespe's Avatar
Join Date: Feb 2005
Location: Cleveland, Ohio
Posts: 1,848
ALOT of experience with the M617 (5 cylinder turbo) and WVO
Closing the store
on your smart phone or tablet.
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Old 09-24-2010, 03:11 PM
is thinning the herd
Join Date: Mar 2010
Location: Columbus, Ohio
Posts: 3,339
The 300SD (w126) is not a rod bender. The SD was made up until 1985. The 300SDL (w126) from 1986 to like 89 was also not a rod bender. The 350SDL (w126) WAS a rod bender, and the 300SD 92+ / S350 (both W140 chassis) were rod benders.

I'd say WVO the W126 with the OM617. People seem to have more experience with the 617 and WVO. Shame to tear up a nice W124 on the stuff.
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Old 09-24-2010, 04:30 PM
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smoke gets in your eyes
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Location: Eastern TN
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There is a value question separate from price. An 84 SD and a 92 2.5 priced the same - everything else being equal, the SD is overpriced or the 2.5 is a steal.

How much documented history is available for each car? How recent is complete suspension work? Any records of major transmission work? Do all the amenities function per the owner manual, particularly the AC?

Do you have details and documentation on the 2.5 rebuild? There are few hands most of us here would trust to properly rebuild an MB engine. I'd ask why it was rebuilt. A 2.5 chain can snap requiring head work and possibly new pistons. The turbo boost system can malfunction resulting in low power and an opportunity for a questionable shop to recommend a rebuild. I'd almost prefer they continued the ruse and not actually touch the bottom end than cut corners and shorten the life of an otherwise good engine.

87 300D
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Old 09-24-2010, 04:44 PM
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They're both $1500. a/c on the 84 blows cold. a/c on the 92 blows hot. When I asked why the 92 was rebuilt he said "the bottom end went out." He also told me the cv joint on the right rear is starting to make a little bit of noise.
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Old 09-24-2010, 05:00 PM
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smoke gets in your eyes
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Location: Eastern TN
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[Sixto thinking out loud] 84 SD with cold AC was probably cared for, 92 2.5 without AC probably not.

Are these cars openly listed for sale? A 2.5 offered at $1500 and still for sale has more wrong with it than meets the eye. Is rust an issue where you are? Accident history? Mary Kaye livery?

A $1500 SD with working AC wouldn't last around here.

87 300D
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Old 09-24-2010, 07:38 PM
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Location: Left Coast
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Get the SD.
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Old 09-24-2010, 08:21 PM
Join Date: Aug 2010
Posts: 111
None. VO is terrible for all diesel engines.

Pick the one you like and buy/make BioDiesel. Leave the raw vegetable oil for the hackers that don't know what they're doing.

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