Did Mercedes ever fix the rod bending problem in the 3.5L or are they all junk?
Gary C.
'85 300D
89 300TE Gasser

As far as I know, the problem was never really cured. They are not all junk though, many folks have had good luck with them, unfortunately as many as half seem to bend rods somewhere along the line.

Unless you plan to buy one with a bad motor and put in a three liter short block, I would avoid them unless I could buy them very very cheaply.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Only Mercedes rebuilt engines are somewhat safe from it.

Unless the owner can hand you a receipt from Mercedes for an engine, avoid all 3.5L S-Class diesels.

I don't think a mb built engine replacement is safe either. Several folks report having a bent rod with them too.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I'd not avoid all... certainly if the body/interior warrants a 3.0L swap.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

the entire rod bending problem isnt the rods themselves (for the most part) its the heads that crack and dump oil into the combustion chambers. so i would guess that i would replace the head and the rods everything else is probibally fine.

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Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

The head on my car was never cracked. The rods bend because they don't have an infinite fatigue life considering the manufacturing tolerances on dimensions and mechanical properties/heat treatment. I tried my best to get a straight answer from MB and didn't. But, when mine was rebuilt by the dealership, it had the same head put back on. There were no problems with the head, period. Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

That's just a pure guess. The real problem is not known and nobody can say for sure. Only MB knows what the problem was and they won't even acknowledge there was a problem.

Since mb won't say, if indeed they actually know, we are left with educated guesses and wag's.

My favorite theory developed by myself and my favorite machinist over a few st pauli girls, is that the block went over the line in stiffness when they overbored to create the 3.5 and is a bit too flexible, causing head gasket sealing problems. The gasket seeps a little and then a little more and when it gets so it leakes enough to fill the combustion chamber with liquid (it only takes about 1.5 cu in.) then when you start the motor the piston comes up and the hydrolock bends the rod just a little. When the rod bends just a little it also twists a little and begins wearng the cylinder a little oval. The situation just gets worse progressively until you have a truly atrocious situation.

Personally I would buy one only with the plan of substituting a 3.0 block when the rod bending problem occurrs, since the 3.0 almost never bends a rod.

Other wise the 3.5s are a pleasure to drive, very very torquey, smooth powerful and reasonably economical.

But I doubt that you would give up all that much with a 3.0 block.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

The only problem with that hypothesis (not a theory since I'm sure you haven't successfully tested it ) is that other engines like the M104 or OM603/2 are more likely to develop head gasket leaks, yet they don't seem to bend their rods. Also I've never heard of coolant losses or other faulty head gasket symptoms associated with the 3.5L rod bending.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

never trust (a) mercedes.

I've asked this before. Apparently it is pot luck with those engines. Some people love them and some hate them. I don't have the world's best luck, so I wouldn't buy one. I have all the trouble I can handle already.

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" We have nothing to fear but the main stream media itself . . . ."- Adapted from Franklin D Roosevelt for the 21st century

OBK #55

1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
The Dee8gonator 1987 560SEC 196,000 miles - Sold
Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
2016 AMG GTS 12,000 miles

Would the complete motor from a 86-87 300SDL bolt in with out modifications?

It it always the same cylinder?

Mercedes rebuilds these motors at their facility in Berlin, beautiful work. The rebuilt motors (not a short block) come with a 48 month or 50000 mile guarantee. A competitive source for these motors is I.G. Burton in Milford De.
302 424 3042. You can see the motor at www.scaffolding.com/mb.

If you purchase a 350 sdl with an original motor, you certainly should factor in the cost of a replacement motor from MB. Any other option would be a waste of money.
Constantine