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View Poll Results: M156 head bolt data poll
0-20k miles
8.59%
20-40k miles
25.78%
40-60k miles
28.91%
60-80k miles
15.63%
80-100k miles plus
18.75%
Head bolt failure
2.34%
Voters: 128. You may not vote on this poll

M156 head bolt data poll

 
Old 08-09-2016, 11:00 AM
  #26  
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Just happen to my 2009 C63, bought the car a few months ago currently at 62K miles. Car is out of warranty, however the dealer with working with MB to get it taken care of.
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Old 08-09-2016, 01:36 PM
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We used Weibull analysis at work to determine the failure rate of poorly designed parts. Think of it as predicting when popcorn is going to pop. Some kernels pop early, most right in the middle, and some pop very late, but in the end, they are ALL going to pop.

And I bet that Mercedes has the Weibull curve plotted for these head bolt failures. I also bet they have weighed the option of paying for a retrofit versus covering the few that fail in the warranty period along with the good will partial coverage of cars bought new but outside of warranty.

Last edited by glennhl; 08-09-2016 at 04:27 PM.
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Old 08-09-2016, 04:12 PM
  #28  
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2007 Mercedes E63 AMG Pano, 2002 Audi A4 1.8t
i did a full factory coolant flush not to long ago to hopefully prolong the headbolts for a bit longer. planning to do a headstud job within the next 6 months.

117k here
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Old 08-09-2016, 05:30 PM
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It's not the coolant, it's a design flaw and material flaw perhaps.
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Old 08-09-2016, 06:03 PM
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Originally Posted by Merc63 View Post
It's not the coolant, it's a design flaw and material flaw perhaps.
pH of the coolant could accelerate the process though.
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Old 08-09-2016, 06:24 PM
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^ this
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Old 08-09-2016, 09:03 PM
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Oh you think the coolant is going to eat away the metal? Ok I guess you have caustic acid as coolant lol.
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Old 08-10-2016, 07:49 AM
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Originally Posted by Merc63 View Post
Oh you think the coolant is going to eat away the metal? Ok I guess you have caustic acid as coolant lol.
No, but corrode it, yes.

Additives in coolant are supposed to inhibit corrosion. It breaks down, coolant becomes less alkaline which can prohibit corrosion/rust.

Maybe I'm not understanding the HB issue, but aren't the failed bolts caused primarily by excessive corrosion?

If they were 404 SS with the same female head none of them would be failing.

I'd bet if the coolant was flushed as frequent as oil changes it would have prolonged failure.
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Old 08-10-2016, 09:29 AM
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No it's a design flaw. The cross sectional has minimal material at the head.
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Old 08-10-2016, 09:42 AM
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Originally Posted by Merc63 View Post
No it's a design flaw. The cross sectional has minimal material at the head.
And corrosion. Have you seen any failed bolts that haven't been corroded?
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Old 08-10-2016, 01:43 PM
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^ this again. heat corrosion and torque all play a role in its failure. some more than others, otherwise these would have failed upon first time reving the engine out. design flaw nontheless
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Old 08-18-2016, 12:27 AM
  #37  
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3% failure rate according to this unscientific but interesting poll. Would love to see a larger sample size. Head bolt era guys should weigh in!
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Old 04-22-2017, 09:40 AM
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So, I spent an hour tallying the failures from the forum, in a post on this thread, but then got denied posting due to inactivity and my research was lost when I tried to go back.


Anyway, here's what I was doing:


I wanted to update the failures for C63, so I gathered everything and found 13 members that reported failures of headbolts on C63.


What I came up with is:
We know when the new headbolts were implemented and how to look for those.
But:
We never saw a picture of a snapped but not rusted old school bolt.


If rust is a factor, what if Mercedes DID implemented anti-corrosion measures, pre-dating the new bolts implementation.


So I set out to refine the information at hand, by the manufacturing date, because in US, this can pre-date the year of the car, by as many as 2 years.
So I set out to guess by subtracting one year from the model of the car.




So I found a total of 13 reports of failure.


Of these only 3 were 2010 cars and of these only one posted that the car was made in the first quarter of 2009.


All other cars were 2008 (model 2009, guessing made in 2008).


Again, my research got deleted, cause I took to long to hit post.


Now, a factor that can skew researching my idea is that some people did not have the Mercedes antifreeze anymore, possibly negating the anti-corrosion measures.
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Old 03-05-2019, 09:05 PM
  #39  
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Bump?
Objectively a <3% failure right by this poll.
I have near 100k miles on the car, only wear item replacement in recent years and plan to drive this until one of us dies... hard to justify a $$$ preventive repair with such a low failure.
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Old 03-05-2019, 09:38 PM
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Originally Posted by Dogtag114 View Post
Bump?
Objectively a <3% failure right by this poll.
I have near 100k miles on the car, only wear item replacement in recent years and plan to drive this until one of us dies... hard to justify a $$$ preventive repair with such a low failure.
116 poll responses out of north of 10,000 C63s produced is statistically meaningless
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Old 03-05-2019, 10:10 PM
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Originally Posted by BLKROKT View Post
116 poll responses out of north of 10,000 C63s produced is statistically meaningless
agree... are there real stats somewhere?
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Old 03-05-2019, 11:07 PM
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Originally Posted by Dogtag114 View Post
agree... are there real stats somewhere?
Nope. But you can be 100% sure that a) as the PFL cars age and the defective headbolts prone to failure continue to rot in coolant, the failure rate will increase, and b) whatever the number is, its underreported due to poor knowledge, diagnosis and reporting of the root cause.

Its not a question of if they will fail, its when.
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