350SDL 6-cylinder diesel: not as good as the older 5-cylinders?

Benzdom · 06-15-2009, 11:07 PM

I just heard an interesting comment about the quality of diesel engines.

The newer 126 8-cylinder engines have many more troubles than the older 5-cylinder engines.

What's your take on this?

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TMAllison · 06-16-2009, 02:57 PM

The 3.5L diesel was a 6 cyl which has come to be known as the "rod bender". Said to have been the worst engine MB has made.

It was used in later W126 SDL's and all W140 300SD's and S350's from 90(?) up through 95. Some of the later long block crate replacement motors were said to have used updated rods. Some of them apparently failed too

The 5 & 6 cyl 3.0L diesels (eg: 617's, 602's & 603's) have all proven very reliable as has the 606 family.

Benzdom · 06-16-2009, 03:28 PM

Thank you, TMAllision.

I'm currently considering either buying a 2000 C230 or an older Turbodiesel.

Considering the economy, the turbodiesel would probably the saver bet.

Your valuable info is very much appreciated.

Goatman · 06-25-2009, 03:26 PM

The updated motors used a new block that allowed the cylinders to stay round. That's what bent the rods....

Best 6 banger combo is the 3.5L with the replacement block. Second best is the 3L 6 in any form.

And to answer your question, the 6 bangers' are worlds better than the 5 cylinder timing chain eaters.

POS · 06-26-2009, 08:09 PM

You'll get better mpg out of a modernish 6-cyl MB gas engine than you will an older TD.

Benzdom · 06-26-2009, 10:09 PM

I found that out.

I must really say I'm very much in favor of buying a 2000 or so E-class.

As much as I like my old 300D, I'm in the mood for some smooth power and speed.

Goatman · 06-27-2009, 01:58 PM

Driving an S-class TD vs the old 300D's is like driving a Volvo and calling it a MB... No comparison. I was looking for a 300D untill I drove an SDL. Then I had to have one.

TMAllison · 06-27-2009, 05:04 PM

Like the SDL, tuna boats also wallow when manuevering aggressively and are underpowered for thier size.

Newer vs older tech (if one can afford it) is usually a no brainer.

Goatman · 06-28-2009, 07:02 AM

Plenty of power on the SDL, you must be thinking of the 300D's...

240D 3.0T · 06-28-2009, 07:30 AM

Quote:

Originally Posted by Benzdom

The newer 126 8-cylinder engines have many more troubles than the older 5-cylinder engines.

I think you mean 6-cylinder, and yes, its true.

Early 3.0L engines were prone to cracking the head if allowed to get too hot.
All 3.5L engines are at risk for bending rods. It was a poor engine design and MB never officially acknowledged there was even a problem.

The 3.0L is a great engine if combined with a later head casting (#17-22), ironically, from the 3.5L.

bgbrown125 · 07-19-2009, 08:34 PM

I have one of the good ones. My 1991 350SD has 242600 miles on it and will still haul #$@! I've owned it for about eight years and it has been and still is one awesome car.
The engine failures that you speak of usually occur fairly early in life IF they are going to occur. Statiscally, less than 50% of the engines ever fail. Granted that is a high probability of failure. "All" is not a fair word.

kayooh · 07-29-2011, 05:58 AM

Quote:

Originally Posted by bgbrown125

I have one of the good ones. My 1991 350SD has 242600 miles on it and will still haul #$@! I've owned it for about eight years and it has been and still is one awesome car.
The engine failures that you speak of usually occur fairly early in life IF they are going to occur. Statiscally, less than 50% of the engines ever fail. Granted that is a high probability of failure. "All" is not a fair word.

The problem should be contributed to a factor other than a faulty design by MB if ALL engines are not affected.

Any thoughts on this?

oldsinner111 · 08-03-2011, 06:49 PM

could have been a metalurgy problem also.When I was a Machinist,some of our bearing races grew .030.

sdlcrazier · 08-19-2011, 08:20 PM

Quote:

Originally Posted by Goatman

Plenty of power on the SDL, you must be thinking of the 300D's...

300sdl is no doubt powerful, quiet and smooth.

bgbrown125 · 03-13-2012, 03:58 PM

I've heard the same "bad" issues with the 350SD. HOWEVER, I had a 1991 350SD for over a decade and sold it a couple of years ago with 275000 miles on her. She would fly and I never had any motor issues with her at all. Great Car! Some of them did have issues...I had a good one!

06-16-2009, 02:57 PM	#2
TMAllison Super Member Garage is empty, add now Join Date: Jun 2008 Location: Bay Area, CA Posts: 835 Drives: 09' E320	The 3.5L diesel was a 6 cyl which has come to be known as the "rod bender". Said to have been the worst engine MB has made. It was used in later W126 SDL's and all W140 300SD's and S350's from 90(?) up through 95. Some of the later long block crate replacement motors were said to have used updated rods. Some of them apparently failed too The 5 & 6 cyl 3.0L diesels (eg: 617's, 602's & 603's) have all proven very reliable as has the 606 family. __________________ T. Allison 85' 300D 311k miles 99' E300 311.5k miles (totaled) 09' E320 Bluetec 66k

06-25-2009, 03:26 PM	#4
Goatman Senior Member Garage is empty, add now Join Date: Oct 2008 Location: MA Posts: 335 Drives: 1987 SDL; 2001 Chevy 2500HD CC, 8.1L, Allison special order; 1970 GTO LS2, 4L60E, under construction	The updated motors used a new block that allowed the cylinders to stay round. That's what bent the rods.... Best 6 banger combo is the 3.5L with the replacement block. Second best is the 3L 6 in any form. And to answer your question, the 6 bangers' are worlds better than the 5 cylinder timing chain eaters. __________________ 2x Grand Champion

06-26-2009, 08:09 PM	#5
POS Member Garage is empty, add now Join Date: Nov 2005 Location: Texas Posts: 134 Drives: 1966 250SE Cab, 1985 500SE Euro, 1985 190e 2.3-16 AMG, 1986 300E LeMons Car	You'll get better mpg out of a modernish 6-cyl MB gas engine than you will an older TD. __________________ 1994 w124 E320 wagon 1985 w201 190E 2.3-16v AMG 1986 w124 300E LeMons race car 1971 w109 300SEL 6.3 vintage race car

06-27-2009, 01:58 PM	#7
Goatman Senior Member Garage is empty, add now Join Date: Oct 2008 Location: MA Posts: 335 Drives: 1987 SDL; 2001 Chevy 2500HD CC, 8.1L, Allison special order; 1970 GTO LS2, 4L60E, under construction	Driving an S-class TD vs the old 300D's is like driving a Volvo and calling it a MB... No comparison. I was looking for a 300D untill I drove an SDL. Then I had to have one. __________________ 2x Grand Champion

06-27-2009, 05:04 PM	#8
TMAllison Super Member Garage is empty, add now Join Date: Jun 2008 Location: Bay Area, CA Posts: 835 Drives: 09' E320	Like the SDL, tuna boats also wallow when manuevering aggressively and are underpowered for thier size. Newer vs older tech (if one can afford it) is usually a no brainer. __________________ T. Allison 85' 300D 311k miles 99' E300 311.5k miles (totaled) 09' E320 Bluetec 66k

06-16-2009, 03:28 PM	#3
Benzdom Junior Member Garage is empty, add now Join Date: Jun 2009 Location: Santa Monica, CA Posts: 52 Drives: 300D	Thank you, TMAllision. I'm currently considering either buying a 2000 C230 or an older Turbodiesel. Considering the economy, the turbodiesel would probably the saver bet. Your valuable info is very much appreciated.

06-26-2009, 10:09 PM	#6
Benzdom Junior Member Garage is empty, add now Join Date: Jun 2009 Location: Santa Monica, CA Posts: 52 Drives: 300D	I found that out. I must really say I'm very much in favor of buying a 2000 or so E-class. As much as I like my old 300D, I'm in the mood for some smooth power and speed.

06-28-2009, 07:02 AM	#9
Goatman Senior Member Garage is empty, add now Join Date: Oct 2008 Location: MA Posts: 335 Drives: 1987 SDL; 2001 Chevy 2500HD CC, 8.1L, Allison special order; 1970 GTO LS2, 4L60E, under construction	Plenty of power on the SDL, you must be thinking of the 300D's... __________________ 2x Grand Champion

07-19-2009, 08:34 PM	#11
bgbrown125 Newbie Garage is empty, add now Join Date: Jul 2009 Location: NC Mountains Posts: 6 Drives: 1994 SL500 E320	350SD I have one of the good ones. My 1991 350SD has 242600 miles on it and will still haul #$@! I've owned it for about eight years and it has been and still is one awesome car. The engine failures that you speak of usually occur fairly early in life IF they are going to occur. Statiscally, less than 50% of the engines ever fail. Granted that is a high probability of failure. "All" is not a fair word.

08-03-2011, 06:49 PM	#13
oldsinner111 Senior Member 1999 Mercedes-Benz S-Class Join Date: Jun 2010 Location: tennessee Posts: 494 Drives: s320 and 300sd	could have been a metalurgy problem also.When I was a Machinist,some of our bearing races grew .030. __________________ 1999 S320 plus 125 nitrous shot hp,modified grille area,and cold air intake,wrapped exhaust manifold,wrapped air duct,cold air,ceramic pads,no cats Borla exhaust one muffler14.4 1/4 mile 1983 300 SD not stock Mobil One ATF diesel rated oil both cars

03-13-2012, 03:58 PM	#15
bgbrown125 Newbie Garage is empty, add now Join Date: Jul 2009 Location: NC Mountains Posts: 6 Drives: 1994 SL500 E320	I've heard the same "bad" issues with the 350SD. HOWEVER, I had a 1991 350SD for over a decade and sold it a couple of years ago with 275000 miles on her. She would fly and I never had any motor issues with her at all. Great Car! Some of them did have issues...I had a good one! Attached Thumbnails

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