Rod Bender True Stories - How it Broke and Why - Page 5 - PeachParts Mercedes-Benz Forum

pawoSD · #61 03-25-2008, 03:39 AM

Quote:

Originally Posted by Bio300TDTdriver

Don't you 2 ever sleep? It's 1:00 on the east coast.

I am still up....and its 3:36am

My question about the rod benders is how is it that some are out there with 200k+ or 250k+ on them with original engines and no signs of failure. Seems odd that these "fluke" engines could have made it so far. Are those just the lucky ones? There's a 350SD for sale near me here that just had a "new engine put in 15k ago" according to the seller. Its a mint, beautiful car, and they only want $6500 for it. Seems fishy. Not that I could (or would) buy it....just wondering why not all of them seem to suffer the fate. ???

t walgamuth · #62 03-25-2008, 07:40 AM

Quote:

Originally Posted by jcciem

PHP Code:


			
could one conclusively say: "350's are junk, stay away from them?"

just wondering.

As a proud owner of a '91 350SD I strongly disagree with the above allegation! There at least three of us on here who own 1990/1991 350SD's or 350SDL's that currently exceed 500,000 miles. Quite an accomplishment when you think how few were built in comparison to all of the 240D's, 300D's, and 300SD's put together. But in my seven years on this forum, there is a non-stop extolling of the virtues of the 240D, 300D, 300SD, my favorite of course "the bulletproof engines". If you put all of the hundreds or perhaps thousands of 240D, 300D, 300SD, owners on this forum together I don't think you have three in the whole bunch, that exceed 500,000 miles. With that huge expanse, of time from the first 240D to the last 300D, if these vehicles were so spectacular, so reliable, so bulletproof, wouldn't you think between all of these owners with such widely available vehicles there should be huge groups, in each category (240D, 300D, 300SD) with mileage meeting or exceeding 500,000 miles? Where are you? Where are you hiding? It's the limited production, mighty '90/'91 350SD/SDL's that are the true reliability, high mileage champions. Rod benders, I've never disputed it, nor do I do so now. However it would appear that among the small group of '90/'91 350SD's and 350SDL's owners on this forum, we own the most reliable long mileage vehicles here. The 350SD's and 350SDL's apparently have had their connecting rod failures, but what exactly is the major engine failure in all of the thousands of 240D, 300D, and 300SD's, that's sending them to the crusher long before they reach 500,000 miles? Enough of the constant bad mouthing against the 350SD/SDL's. I really can't take it any more. Lets concentrate on finding the causes of all the catastophic engine failures on the 240D, 300D and 300SD's that's sending most of them to an early
(pre 500,000 mile) grave!

'87 560SL 150,000
'94 SL500 40,000
'91 350SD 515,000 that's right 515,000 miles not kilometers

I think maybe you should go eat worms.

Tom W

t walgamuth · #63 03-25-2008, 07:41 AM

Quote:

Originally Posted by Brian Carlton

Do you have any evidence of a head gasket failure that occured prior to the subject connecting rod failure on a 603.970 or 603.971?

Did your vehicle suffer a connecting rod failure? I don't believe that it did.........and, therefore........your head gasket failure is irrelevant to the topic.

You've got a theory with no supporting evidence.........evidence that should be available from those who suffered the rod bearing failure.........if the evidence exists.

We're discussing your theory..........correct?

I could come up with a theory that a rock was kicked up off the roadway and got sucked into the intake and magically went though the turbo and into the combustion chamber and bent the rod. I don't have any evidence of that..........but, I'd like you to believe it because my machinist came up with the idea. Would that be acceptable to you? I think that this rock theory has some merit.........and I'm going to put it forth in the future..........how about that?

So.....you have no evidence to support any other theory.

Tom W

#64 03-25-2008, 07:46 AM

Quote:

Originally Posted by t walgamuth

So.....you have no evidence to support any other theory.

No evidence has been found to support any theory. The only people that know the real reason(s) are MB's R&D engineers.

t walgamuth · #65 03-25-2008, 08:10 AM

If they put in stronger rods and that did not solve the problem and the next engine they built had 3.0 instead of 3.5 liters that suggests that the displacement was the problem.

That is evidence.

They are not saying what the problem is for liability reasons, obviously

Tom W

Lampbum2 · #66 03-25-2008, 08:13 AM

Mercedes has upgraded rods for these engines, I priced them for $200.00 @ rod.

Brian Carlton · #67 03-25-2008, 10:08 AM

Quote:

Originally Posted by t walgamuth

So.....you have no evidence to support any other theory.

Tom W

Again, the discussion was your theory.

In your theory, there should be evidence to support it. The fact that there is no evidence of head gasket failure prior to the rod bending event tends to discount your theory.

My theory is the theory of the rock. I'm going to put forth that theory in the future if you continue with your theory. I have no evidence of the rock internal to the cylinder and you have no evidence of a head gasket failure.

We both have poor theories.

Brian Carlton · #68 03-25-2008, 10:12 AM

Quote:

Originally Posted by ForcedInduction

No evidence has been found to support any theory. The only people that know the real reason(s) are MB's R&D engineers.

By Tom's theory, we must conclude that the engineers do not know the true cause of the problem. If the bending of the rod is caused by a head gasket leak, it hardly makes any sense to strengthen the rod slightly.

So, to accept Tom's theory, one must also conclude that M/B is clueless to the problem.

t walgamuth · #69 03-25-2008, 10:44 AM

My theory is possible and there is good reasoning to support it.

You have not proposed anything better but have decided to attack my theory for some unknown reason.

The rock theory is impossible and you know it.

Tom W

airbus · #70 03-25-2008, 12:29 PM

Sorry guys, I couldn't help myself

http://www.peachparts.com/shopforum/showthread.php?t=217481

Hatterasguy · #71 03-25-2008, 12:33 PM

Quote:

Originally Posted by Bio300TDTdriver

Don't you 2 ever sleep? It's 1:00 on the east coast.

No, sleep when your dead!

JimSmith · #72 03-25-2008, 05:03 PM

I have posted "my" theory on this several times.

I bought one of these, a taupe 1991 350SD with a cream leather interior in pristine condition with about 75,000 miles on the odometer. I loved the car. Fit my family, was safe and got reasonable mileage. And it was a Diesel that I was certain would last forever. The rod bending phenomena was already known to MB and to the small group of owners posting on various sites on the relatively new internet car forums. I was blissfully ignorant.

At about 155,000 miles it began to have a loping idle and would blow a puff of smoke out, that would sometimes turn into a smoke ring. I took it to the dealership and assumed I was going to have to rebuild the head. I was not happy about this but figured the aluminum head demon had bitten me. The service writer at the time tells me it is more likely a bent rod. I ask why and he sort of shrugs and tells me they have seen it before. More often than failed heads or failed head gaskets.

The dealership service head cheese calls me and tells me they took the head off and I have a bent rod on two cylinders. I don't recall which two. I tell them I will be over to have them show me how they made that determination. I went over and they showed me they measure the height of the piston at TDC and compare it to the others. 4 are good, two are low. Bent rods. I ask about the head. No problem. They even suggest that if I have it repaired the head is likely good to go as is. I throw a **** fit, and ask how I could have bent a rod. I am told there is nothing I could do to bend a rod. The car won't let me. I ask how it happened and they say they don't know, but it does happen. I am an MB Club member and at the time they gave 25% on parts and 10% on labor. I get an estimate, something under $7k. I authorize the repair.

I examined the head and the head gasket while I was there. Nothing I saw, and the mechanic doing the rebuilding confirmed there was no sign of any head component or head gasket failure. I tell them I want the guides and seals changed and the valve seats reground. This adds a few hundred bucks to the repair. So it is around $7,500 with new all kinds of stuff.

I get the car back. It has a 12,000 mile, one year warranty. At about 13,000 miles it is smoking again. I now go back in and ask what, specifically they did. They try to tell me it is likely the turbo seals. I tell them until they can explain how the 7,500 dollars I just spent fixed the rod bending problem, I am not going to do anything. The service manager tries to calm me down, saying all kinds of meaningless crap about how the problem was rare and they are sure they fixed it even though he can't tell me what changed. I tell him the guy who wrote up the original repair order told me it was bent rods before the head came off and that sure makes it sound like more than a rare problem.

I go home and start searching the internet. I find MBShop.com and a link to a bunch of links about this problem. It is clear I am being screwed by an old man at the dealership who runs the service department. I go back with about 50 printed pages of stuff I gleaned off the internet about this problem, including groups forming to press MB with a class action suit, and go to the sales department. I start a loud discussion about the subject, and likelihood I would be better off buying a VW Diesel, with the sales guy I now deal with, who reminds me he did not sell me the car. He gets up and says he is going to speak to the management.

He comes back and tells me the management has agreed to give me full Blue Book value for my car (about $7k back then, before considering it was smoking and had a rod bender engine in it), the full $7,500 they charged for the repair as a trade on any new or used car in inventory. I find a silver 1998 E300D TurboDiesel. We work a "deal" out and I go to a Benz dealer in New Haven to see what kind of deal they will give me. Basically a plain white with black MB Tex car, no significant options, slightly higher asking price and they offer me $3500 for my 350SD. I took the Carriage House of New London deal.

Based on much reading I did at the time the issue, as I see it, is the rods don't have an infinite fatigue life, as built. This is due to a combination of issues, many interdependent, some not. But the production methods seem to be producing borderline rods. Not all are good, not all are bad. Due to dimensional tolerances of finished parts, their starting material properties and their as heat treated properties, all of which have tolerances. You get bad ones and the rods suffer fatigue failures at something over 65,000 miles. Mine failed in all likelihood around twice that mileage. After that the rate of failure is lower meaning if you survive the first 200,000 you likely have next to zero chance of a fatigue failure because the rods met the design specifications with a bit of margin.

Redesigning the rods to be heavier may help, until you stress them at full speed. Higher mass means higher stresses. This is not, in an already settled and now dimensionally controlling environment, a path to success.

I have heard all kinds of theories about hydrolocks, ingesting chunks of the scum that collects in the intake manifold downstream of the EGR valve, flexible blocks and so on. I see no hard evidence those are the problems. And, the displacement selection of an engine in Germany is made to comply with tax codes. You will notice all car companies have offerings at the break points. When designing a new engine the manufacturer always designs around the "bread and butter" models in the line up. 3.0 liters is a break point for turbocharged engines. Insurance is paid, by the way, on hp rating regardless of body style. They figure 200 hp has a fixed potential for damage liability, regardless of whether or not it is in a coupe or sedan or station wagon.

As for those bulletproof W123's, well, I have only ruined one mechanically (my son ran it without oil after it had well over 300,000 mles) yet I have retired several due to body rot. Better rustproofing in later cars makes them last longer. And, a 240D is so loud to drive it 500,000 miles averaging 70 mph or so means you will likely suffer a hearing impairment. A W126 or W140 is another story altogether. But I don't think you will find W140s and later cars in use in Beirut or other rough cities twenty five years after they have gone out of production, in significant numbers. The bulletproof label is one that has been earned, literally. I have never been stranded by a W123. I do not think I could say the same for the W140 - I doubt it would run without any electricity, for example. A W123 will. And an ordinary Joe like me can keep a W123 running indefinitely.

Jim

t walgamuth · #73 03-25-2008, 05:17 PM

Quote:

Originally Posted by JimSmith

I have posted "my" theory on this several times.

I bought one of these, a taupe 1991 350SD with a cream leather interior in pristine condition with about 75,000 miles on the odometer. I loved the car. Fit my family, was safe and got reasonable mileage. And it was a Diesel that I was certain would last forever. The rod bending phenomena was already known to MB and to the small group of owners posting on various sites on the relatively new internet car forums. I was blissfully ignorant.

At about 155,000 miles it began to have a loping idle and would blow a puff of smoke out, that would sometimes turn into a smoke ring. I took it to the dealership and assumed I was going to have to rebuild the head. I was not happy about this but figured the aluminum head demon had bitten me. The service writer at the time tells me it is more likely a bent rod. I ask why and he sort of shrugs and tells me they have seen it before. More often than failed heads or failed head gaskets.

The dealership service head cheese calls me and tells me they took the head off and I have a bent rod on two cylinders. I don't recall which two. I tell them I will be over to have them show me how they made that determination. I went over and they showed me they measure the height of the piston at TDC and compare it to the others. 4 are good, two are low. Bent rods. I ask about the head. No problem. They even suggest that if I have it repaired the head is likely good to go as is. I throw a **** fit, and ask how I could have bent a rod. I am told there is nothing I could do to bend a rod. The car won't let me. I ask how it happened and they say they don't know, but it does happen. I am an MB Club member and at the time they gave 25% on parts and 10% on labor. I get an estimate, something under $7k. I authorize the repair.

I examined the head and the head gasket while I was there. Nothing I saw, and the mechanic doing the rebuilding confirmed there was no sign of any head component or head gasket failure. I tell them I want the guides and seals changed and the valve seats reground. This adds a few hundred bucks to the repair. So it is around $7,500 with new all kinds of stuff.

I get the car back. It has a 12,000 mile, one year warranty. At about 13,000 miles it is smoking again. I now go back in and ask what, specifically they did. They try to tell me it is likely the turbo seals. I tell them until they can explain how the 7,500 dollars I just spent fixed the rod bending problem, I am not going to do anything. The service manager tries to calm me down, saying all kinds of meaningless crap about how the problem was rare and they are sure they fixed it even though he can't tell me what changed. I tell him the guy who wrote up the original repair order told me it was bent rods before the head came off and that sure makes it sound like more than a rare problem.

I go home and start searching the internet. I find MBShop.com and a link to a bunch of links about this problem. It is clear I am being screwed by an old man at the dealership who runs the service department. I go back with about 50 printed pages of stuff I gleaned off the internet about this problem, including groups forming to press MB with a class action suit, and go to the sales department. I start a loud discussion about the subject, and likelihood I would be better off buying a VW Diesel, with the sales guy I now deal with, who reminds me he did not sell me the car. He gets up and says he is going to speak to the management.

He comes back and tells me the management has agreed to give me full Blue Book value for my car (about $7k back then, before considering it was smoking and had a rod bender engine in it), the full $7,500 they charged for the repair as a trade on any new or used car in inventory. I find a silver 1998 E300D TurboDiesel. We work a "deal" out and I go to a Benz dealer in New Haven to see what kind of deal they will give me. Basically a plain white with black MB Tex car, no significant options, slightly higher asking price and they offer me $3500 for my 350SD. I took the Carriage House of New London deal.

Based on much reading I did at the time the issue, as I see it, is the rods don't have an infinite fatigue life, as built. This is due to a combination of issues, many interdependent, some not. But the production methods seem to be producing borderline rods. Not all are good, not all are bad. Due to dimensional tolerances of finished parts, their starting material properties and their as heat treated properties, all of which have tolerances. You get bad ones and the rods suffer fatigue failures at something over 65,000 miles. Mine failed in all likelihood around twice that mileage. After that the rate of failure is lower meaning if you survive the first 200,000 you likely have next to zero chance of a fatigue failure because the rods met the design specifications with a bit of margin.

Redesigning the rods to be heavier may help, until you stress them at full speed. Higher mass means higher stresses. This is not, in an already settled and now dimensionally controlling environment, a path to success.

I have heard all kinds of theories about hydrolocks, ingesting chunks of the scum that collects in the intake manifold downstream of the EGR valve, flexible blocks and so on. I see no hard evidence those are the problems. And, the displacement selection of an engine in Germany is made to comply with tax codes. You will notice all car companies have offerings at the break points. When designing a new engine the manufacturer always designs around the "bread and butter" models in the line up. 3.0 liters is a break point for turbocharged engines. Insurance is paid, by the way, on hp rating regardless of body style. They figure 200 hp has a fixed potential for damage liability, regardless of whether or not it is in a coupe or sedan or station wagon.

As for those bulletproof W123's, well, I have only ruined one mechanically (my son ran it without oil after it had well over 300,000 mles) yet I have retired several due to body rot. Better rustproofing in later cars makes them last longer. And, a 240D is so loud to drive it 500,000 miles averaging 70 mph or so means you will likely suffer a hearing impairment. A W126 or W140 is another story altogether. But I don't think you will find W140s and later cars in use in Beirut or other rough cities twenty five years after they have gone out of production, in significant numbers. The bulletproof label is one that has been earned, literally. I have never been stranded by a W123. I do not think I could say the same for the W140 - I doubt it would run without any electricity, for example. A W123 will. And an ordinary Joe like me can keep a W123 running indefinitely.

Jim

Very good post, Jim. Where did you find the information about the rods suffering from fatigue?

Tom W

JimSmith · #74 03-25-2008, 05:22 PM

To be absolutely clear, Tom, I made it up. After looking at my car and reading about another 30 to 50 cases posted on the internet at the time, I concluded that is the only way some can fail and some can be good. As I noted on the other thread, relatively few can be bad and make a large number of MB customers very unhappy. I believe the design is sound analytically, but not compatible with the production methods used to make rods. Not enough margin and that was likely due to the competition for real estate inside the engine when everything got tighter as the displacement was enlarged. Jim

JimSmith · #75 03-25-2008, 05:23 PM

Almost every other scenario makes the likelihood of any population of engines being immune as miles are built up less likely. Jim