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  #1  
Old 02-28-2019, 10:08 PM
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603.97 Questions (Yes, the Rod-Bender)

I'm now rolling a '91 350SD and loving it. I'm familiar enough with the 603.96, but the .97 has me asking a couple of questions I can't find answers for. So...A couple questions for those with more knowledge than I...

1: The car has 169K miles on it (just clicked over this evening). Engine is perfectly smooth, super quiet, leak-free, has ZERO blowby, has ZERO chain stretch, produces ZERO smoke, and seems to use no oil (I haven't owned it long enough to keep track long-term). Is this engine a survivor? Has it been replaced? Have the rods been redone? Is there even any way to tell? I have some paperwork on the car, but there's a wide gap from ~1994-2006 in its history, so not much help there.

2: I can hear the turbo in the cabin when under full boost (and only when under full boost), a faint whistle and a hushed "whoosh". My SDL never made turbo noise and I'm not sure if its normal on this car. I know there's some sort of difference with the turbo, not sure what. They're both Garrett. I've been unable to find an exhaust or intake manifold leak, the turbo makes 14PSI boost, the wastegate appears to operate properly, and the exhaust pipe is solid all the way to the rear of the car. To be clear, we're not talking about a lot of noise here, the only way to even hear it is to have the radio off and the HVAC fan on low speed.

I'm not so much worried about #2 since it seems to have no impact on how the car runs or drives. I'd be lying if I said I wasn't just slightly worried about #1 given the reputation these cars have (and my own admission multiple times on this forum that I'd never own a 3.5). We all have our faults right?

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'11 Honda Accord EX - "The Daily" 73K
'91 560SEL - "Delta 88" 193K
'91 350SD - "Jest-D" 176K (Sold 12/20/20)
'94 BMW 525i - "The Red Car" 181k
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  #2  
Old 02-28-2019, 10:55 PM
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I don't have rod bender, but it might be worth looking look for a metal tag on the engine block with the term Tauschaggregat. That would mean a replacement engine. My understanding is these were improved versions.
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  #3  
Old 02-28-2019, 11:20 PM
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Well that's more information than I had to go on earlier. A search of that term goes to a few threads on this forum and elsewhere saying where to look and what to look for. I can say with certainty that it's not a replacement engine now. Still has the serial number embossed in the block by the IP and no "Tauschaggregat" tag anywhere on the engine or bell housing. #17 head casting.
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'11 Honda Accord EX - "The Daily" 73K
'91 560SEL - "Delta 88" 193K
'91 350SD - "Jest-D" 176K (Sold 12/20/20)
'94 BMW 525i - "The Red Car" 181k
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  #4  
Old 02-28-2019, 11:29 PM
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You can check the datacard to see if that’s the original engine.

They don’t all bend rods. If 5% do, that’s a lot.

My uneducated opinion is EGR contributes to bent rods. Do what you will with that hypothesis.

Sixto
98 E320s sedan and wagon
02 C320 wagon
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  #5  
Old 03-01-2019, 12:07 AM
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Quote:
Originally Posted by sixto View Post
My uneducated opinion is EGR contributes to bent rods. Do what you will with that hypothesis.
EGR delete was the very first thing done to the car. One of the myriad problems I had with it was due to the EGR valve being stuck wide open. Engines don't run well on their own exhaust, the noises they make proclaim it loudly...
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'11 Honda Accord EX - "The Daily" 73K
'91 560SEL - "Delta 88" 193K
'91 350SD - "Jest-D" 176K (Sold 12/20/20)
'94 BMW 525i - "The Red Car" 181k
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  #6  
Old 03-01-2019, 12:27 AM
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Congrats on the new car Diseasel. I had looked into those cars years ago on several ocassions my research lead me to believe the oval pistion and bent rod were a result of poor fuel quality on this side of the pond. It was 2012 in canada when diesel fuel quality was that of europe in the 90s. Of course thats just my opinion I know lots of other speculation exists.
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  #7  
Old 03-01-2019, 03:52 PM
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I have 195k on my 603.971, 50k are mine. Original engine. Quite sure I do not have the rod bending problem. I do have a few other issues : no apparent blowby, some oil leaks, an injector that has started *pinging*, ... they are just waiting for me to get some free time or an alternative daily driver. Engine purrrrrs, starts right up, still has egr. I cannot hear my turbo from inside the car but it must work - I've been told if it didn't work I'd be complaining about power - not really sure I would recognize the sound anyway - my w140 is Quiet.

When looking through the online Startek docs for the W126 '91 350SD or 350SDL I haven't noticed any glaring differences with my manuals or what I find poking around in/on the engine.
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  #8  
Old 03-01-2019, 10:24 PM
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Quote:
Originally Posted by sixto View Post
You can check the datacard to see if thatís the original engine.
I did exactly that this evening. Both engine and transmission are original to the car. I swear I'm a lightning rod for this kind of stuff. SDL had factory original engine and trans as well, #14 head had never been removed until I took it off to have the valves done. Crack free and warp free. Maybe I should buy a lottery ticket...
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'11 Honda Accord EX - "The Daily" 73K
'91 560SEL - "Delta 88" 193K
'91 350SD - "Jest-D" 176K (Sold 12/20/20)
'94 BMW 525i - "The Red Car" 181k
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  #9  
Old 03-07-2019, 08:12 PM
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Just to close out this thread in case someone runs across it in the future, the excessive turbo noise was caused by missing rubber gaskets at the false firewall and side rails of the hood. Stole the missing parts off the SDL and transplanted them over and it made a profound difference in the amount of noise making it in the cabin. Who'd have thought? Seems that's all it was since the noise level is now comparable with that of the SDL and I changed nothing else.
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'11 Honda Accord EX - "The Daily" 73K
'91 560SEL - "Delta 88" 193K
'91 350SD - "Jest-D" 176K (Sold 12/20/20)
'94 BMW 525i - "The Red Car" 181k
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  #10  
Old 03-07-2019, 08:51 PM
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Unhappy RIP

Sorry about your 300SDL. I just saw that. :-(
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  #11  
Old 03-08-2019, 01:12 AM
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Quote:
Originally Posted by Mikebear79 View Post
Sorry about your 300SDL. I just saw that. :-(
It sucks and I'm still upset about it (probably will be for a long time), but it was a valuable learning experience for me. Ironically, the SD has a perfect interior and nearly perfect body (easily a 9.5/10), but has tons of mechanical and electrical problems. All of them are things I've ironed out or repaired on the SDL.

I bought the SDL back from the insurance company and still stayed in the black compared to what I had in it. Now I have a parts car with all the parts and electrical bits I need to make the SD perfect. So the SDL (or parts of it at least) will live on in the SD. Since the SD doesn't need interior or paint work, when I finish transplanting parts, I'm basically done for a minimum of money laid out.

Funny how things like that work out...
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'11 Honda Accord EX - "The Daily" 73K
'91 560SEL - "Delta 88" 193K
'91 350SD - "Jest-D" 176K (Sold 12/20/20)
'94 BMW 525i - "The Red Car" 181k
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  #12  
Old 05-14-2020, 05:46 PM
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Hey guys, I am the owner of one of these 1991 350SDL beauties and I'm trying to figure out what's wrong. I didn't really know where to post so I figured I would try out this thread. About a year and a half ago, the accelerator lost power while I was driving and wouldn't respond even when I pushed it to the floor. I pulled over and put it in park, it started smoking. Thick white smoke. I went to turn it off and it began dieseling. I finally manually turned it off with the stop lever under the hood. Hauled her home behind our truck and have since been trying to figure out what's wrong. It's gotten to the point where she won't start, but the engine will turnover. I checked the injectors and got any gunk out of them, I tested the glowplugs and the relay (all but one are operating properly), and I carefully replaced the seals on the injection pump. I've read so much about these cars being rod benders with oil leaking into a cylinder and I just don't know what to do. Any help would be appreciated. I'll provide as much information as I can!
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  #13  
Old 05-14-2020, 08:52 PM
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Have you drained the oil? Milkshake??

White smoke? Sounds like water. Seems these engines can breach the HG multiple ways.

Mine went oil into the coolant. Notionally the oil is always higher pressure, and that’s all it is. The car ran like a top. Told my info to take his time and he did...

Going to run JD Cool Gard II in there after. Though I’m a big G-05 fan, the JD coolant is a superior chemistry for mixed metal engines.
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Current Diesels:
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1991 350SD (113k)
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1985 300D (233K)
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  #14  
Old 05-14-2020, 10:49 PM
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Quote:
Originally Posted by hwil1231 View Post
Hey guys, I am the owner of one of these 1991 350SDL beauties and I'm trying to figure out what's wrong. I didn't really know where to post so I figured I would try out this thread. About a year and a half ago, the accelerator lost power while I was driving and wouldn't respond even when I pushed it to the floor. I pulled over and put it in park, it started smoking. Thick white smoke. I went to turn it off and it began dieseling. I finally manually turned it off with the stop lever under the hood. Hauled her home behind our truck and have since been trying to figure out what's wrong. It's gotten to the point where she won't start, but the engine will turnover. I checked the injectors and got any gunk out of them, I tested the glowplugs and the relay (all but one are operating properly), and I carefully replaced the seals on the injection pump. I've read so much about these cars being rod benders with oil leaking into a cylinder and I just don't know what to do. Any help would be appreciated. I'll provide as much information as I can!

Sounds like head gasket or turbo seals. There is a potential problematic oil feed to the head just ahead of the number one cylinder on the 603 blocks. Gasket failure can feed oil into the first cylinder.

Just remove the connector to the turbo to see if it is the turbo seal. Strange it will not start though.

Also removal of the number one glow plug. To see if the cylinder is spitting oil out. Tie down the injection pump shutoff first of course. I do not think the bent rod syndrome just starts up out of the blue like you experienced. It takes time and wear to allow the oil to get past the piston. Nothing Is written in stone. The not starting leads me to suspect the chain may have jumped timing over the other choices. Easy to check on these engines.

As for the rod bending issue. Mercedes never released the cause officially. To the best of my knowledge. Perhaps for liability reasons. The block is substantially weaker than the 3 liter block. Was obvious on examination. I still feel that plays into it. Why some fail and others may not. Could be as simple as the block casings quality varied a lot. Take your pick of theories. If I had one I would not idle it a lot.

Yet as they say. Opinions are like rectums. Everyone has one.

It is also not too late to start your own thread. That will produce far more help than I can give with my limited experience. This is probably the best support site for these older Mercedes diesel cars.

Last edited by barry12345; 05-14-2020 at 11:10 PM.
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  #15  
Old 07-11-2020, 11:31 AM
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Quote:
Originally Posted by barry12345 View Post
Sounds like head gasket or turbo seals. There is a potential problematic oil feed to the head just ahead of the number one cylinder on the 603 blocks. Gasket failure can feed oil into the first cylinder.

Just remove the connector to the turbo to see if it is the turbo seal. Strange it will not start though.

Also removal of the number one glow plug. To see if the cylinder is spitting oil out. Tie down the injection pump shutoff first of course. I do not think the bent rod syndrome just starts up out of the blue like you experienced. It takes time and wear to allow the oil to get past the piston. Nothing Is written in stone. The not starting leads me to suspect the chain may have jumped timing over the other choices. Easy to check on these engines.

As for the rod bending issue. Mercedes never released the cause officially. To the best of my knowledge. Perhaps for liability reasons. The block is substantially weaker than the 3 liter block. Was obvious on examination. I still feel that plays into it. Why some fail and others may not. Could be as simple as the block casings quality varied a lot. Take your pick of theories. If I had one I would not idle it a lot.

Yet as they say. Opinions are like rectums. Everyone has one.

It is also not too late to start your own thread. That will produce far more help than I can give with my limited experience. This is probably the best support site for these older Mercedes diesel cars.

Thank you! I'll check out that stuff and see what's up. I was initially thinking it was the head gasket, but wasn't too sure how to test that theory. I don't have the service manual, but I'm trying to find one for a reasonable price.

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