Looking for a piston for a 91 350 sdl per previous post. Cheapest I can find new $295.50. Can get a piston for 94 3.4l for $125 Anybody know the difference between these?

The differences between a piston for petrol engine (what's that M104?) and a diesel engine piston will be huge. For starters the compression ratio in the two engines is very different. On the whole diesel engines have a higher compression ratio than petrol engines and thus need stronger (and often heavier) pistons / components.

Just looking at the the swept volume displacement and saying "Oh that's almost 3.5 litres so it will do" won't work. Look at the specifications of the engines on wikepedia =>

List of Mercedes-Benz engines - Wikipedia, the free encyclopedia

Mercedes-Benz OM603 - Wikipedia, the free encyclopedia

Mercedes-Benz M104 engine - Wikipedia, the free encyclopedia


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You might be able to get more information about the piston you require on this site

MAHLE Product Catalogue

Mahle may have made pistons for your engine. You'll have to check.

Kolbenschmidt might have made them - I don't have a link for their catalogue though.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

these are both the 3.4L L6 diesel 603.9 engines. I've been working off and on on diesels for 30 years and am not quite that stupid to think I could put a gas piston in a diesel engine. The ring kits for these pistons are the same part number. The only possible difference I can think of is wrist pin diameter and connecting rod width. The top profile of the pistons is identical. Thanks for the sites listed.

I apologise I was barking up the wrong tree.

I didn't realise they made 3.4 litre OM603s - I thought they were just 3.0 and 3.5s

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If the rings are the same part number then you're about half way there! The Mahle site is good for piston dimension information (if they ever made them)

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Check the weight. Depending on revisions / replacements one of the pistons could have an oil cooling channel.

IIRC there were at least 4 different piston revisions for the 3.5.

And it is 3.5L (well 3.449 if you want to get picky!).

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Ah ha - now I see what's happened...

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

I think one is from 1994 and one is from 1991. But I'm not sure.

__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

Sixto could weigh in on this to offer some clarity I would think. I have a 91 3.5L out of a 350SD. Your welcome to the piston for free. But, a few headbolts stripped out, and would require quite a long drillbit to reach down through the cam towers to drill them out. On another note, how are you recovering so far?

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1987 300SDL #1, 1987 300SDL #2, 1980 240D, 1982 300SD, 1994 S350, 1990 350SDL, 1991 350SD, 1985 300D, 2005 E320CDI

Gone, but not forgotten: 1981 300SD, 1982 300SD, 1987 300SDL, 1983 300TD, 1980 300CD, 1981 300SD #2, 1987 300D, 1987 300TDT, 1980 300D

Also, why do you only need one piston?

That said, EPC only shows one part number (A6030301617) for the 603.970, .971, and .972. Odd they don't show any revisions since I've seen other documentation about the oil cooling channel being added back in around 1995.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

I have to correct myself, there are actually 4 different pistons listed,
A6030301617 - up to engine 971 018445
A6030301817 replaced by,
A6030301917 replaced by,
A6030302117 - as of engine 971 018446

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Recovery going well, left knee replaced last Nov., right hip in August. In therapy and walking without a cane. Thanks for the offer, I still can't ride that far in a car. If you drill the head off the bolts, the head will lift off, then you can get on the bolt with a pair of vise grips, a block of wood on the block and a pry bar between the vise grips and wood, a little upward pressure and the bolts should unscrew. Don't know how easy the bolt head will drill though. Could be a bugger. You should be able to sell the head if it is OK. I'll have to wait awhile before I could come up to help but will think about it as an option. Thanks for the offer!

Gross stupidity. I violated one of my own rules, Alzheimer's strikes again. Didn't tape off the holes when I pulled the intake crossover. Put on a new timing chain on, the master link went flying off through the air. Had another master link. Guess where the lost one went. Bang, crunch, busted piston.

Great to hear about your recovery. I'm see if I can locate a drill bit (cobalt pref) long enough to safely pass through the cam towers and drill them out. Here it is on the stand just after the swap when we removed it. It's been in the shop, on the stand, just fighting gravity for months. Look close, I think it knows the end is near. Ha.

Attached Thumbnails

 

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1987 300SDL #1, 1987 300SDL #2, 1980 240D, 1982 300SD, 1994 S350, 1990 350SDL, 1991 350SD, 1985 300D, 2005 E320CDI

Gone, but not forgotten: 1981 300SD, 1982 300SD, 1987 300SDL, 1983 300TD, 1980 300CD, 1981 300SD #2, 1987 300D, 1987 300TDT, 1980 300D

Three years!

Well, then, you are certainly smarter than all the engineers at General Motors!

They thought they could do it in the 1980s.

__________________
Strelnik
Invest in America: Buy a Congressman!

1950 170SD
1951 Citroen 11BN
1953 Citroen 11BNF limo
1953 220a project
1959 180D
1960 190D
1960 Borgward Isabella TS 2dr
1983 240D daily driver
1983 380SL
1990 350SDL daily driver alt
3 x Citroen DS21M, down from 5
3 x Citroen 2CV, down from 6