M156 head bolt problems
 

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Thanks to bhamg for compiling these pertinent threads!

Mod "splinter" PM'd me to say this thread will become a sticky shortly. Thanks splinter! Very interested in seeing where it takes us!

Thanks for getting it done. Makes it easier to track all of the threads.

I have a few friends that work as techs in the dealer and from talking to them you the bolts are the issue. The bolts tend to stretch causing a leak. New head bolts have been made by mb. In most cases this will be done under warranty if that is your care is still under warranty. I personally don't care as if this happens i will just do a nice head work by roger the guy that does all my cars and but some ARP bolts in. Hope this helps.....

We have seen this problem on many cars. We have worked with ARP to design a head stud to work with the M156/M159. The material used is Custom Age 625+ and is much stronger than any torque to yield bolt. We have these in stock and ready to ship, and we suggest these to anyone that is about to remove the heads from an engine.

http://weistec.com/images/m156studs1.jpg

http://weistec.com/images/m156studs3.jpg

http://weistec.com/images/m156block2.jpg

For more information, please click on the link below. Thanks!

http://weistec.com/m156studs.html

Weistec Engineering

I agree That this is the Best option to go with , i don't know why anyone would want go any other way....

I have a year+ left on the factory warranty. If we see higher rate of failure as many of the M156 cars approach and exceed the 40k mile mark I'll get my extended 7/100 warranty refunded from MB and head to Weistec to have the ARP replacements installed and some additional head work done upon the expiration of the original warranty. The situation is still very fluid but I think we'll know a lot more by the end of 2012 as to how widespread the problem is (will be).

Another head bolt failure, this one on morganb's car, post #156:

https://mbworld.org/forums/c63-amg-w...ad-news-7.html

Thanks for posting the sticky. This needs lots of follow up.

Quote:
Originally Posted by bhamg https://mbworld.org/forums/images/buttons/viewpost.gif
My guess is that MB has already tested many of the old style head bolts that have been pulled from engine assembly as well as normal parts stock. They know what to expect...we don't. The situation reminds me of the infamous Ford Pinto case - and no, I'm not comparing deaths to engine replacements or drawing parallels between our concerns and those of the Ford victims - that I case-studied in B school. These are very different cases. Nonetheless, apparently the Pinto case revealed to the public-at-large a corporate decision-making process heretofore unknown.

Abstract
The cases involving the explosion of Ford Pinto's due to a defective fuel system design led to the debate of many issues, most centering around the use by Ford of a cost-benefit analysis and the ethics surrounding its decision not to upgrade the fuel system based on this analysis.

ANALYSIS
Although Ford had access to a new design which would decrease the possibility of the Ford Pinto from exploding, the company chose not to implement the design, which would have cost $11 per car, even though it had done an analysis showing that the new design would result in 180 less deaths. The company defended itself on the grounds that it used the accepted risk/benefit analysis to determine if the monetary costs of making the change were greater than the societal benefit. Based on the numbers Ford used, the cost would have been $137 million versus the $49.5 million price tag put on the deaths, injuries, and car damages, and thus Ford felt justified not implementing the design change. This risk/benefit analysis was created out of the development of product liability, culminating at Judge Learned Hand's BPL formula, where if the expected harm exceeded the cost to take the precaution, then the company must take the precaution, whereas if the cost was liable, then it did not have to. However, the BPL formula focuses on a specific accident, while the risk/benefit analysis requires an examination of the costs, risks, and benefits through use of the product as a whole. Based on this analysis, Ford legally chose not to make the design changes which would have made the Pinto safer. However, just because it was legal doesn't necessarily mean that it was ethical. It is difficult to understand how a price can be put on saving a human life.

100% correct. If this was a seat belt bolt that sheared off or a smog sensor going bad creating lots of pollution, DOT and the EPA would be all over it. But if the engine in your $65K+rich guys car blows up, the govt could care less. MBZ is most likely looking at the cost compared to the potential loss of brand reputation based on BMW M3 and Porsche 996 engine failure experience. Chances they will stone wall owners that don't have failures and work a deal out with those that have failures out of warranty. The cost to retro fit the head bolts at a dealer is most likely around $3-$4K

... if you don't cause any other damage from the coolant leak :)

I've been wondering whether it's possible for a head bolt to fail one at a time or whether it's always case of immediate, concurrent multiple failures leading to rapid coolant loss. I think we have found an answer...and it is not good IMO. Can an engineer weigh in as to how ONE bolt can fail while the others are seemingly OK, or (as I believe) it's a case of where the others only LOOK OK, they are in fact also not clamping at original torque values and imminent failure is just around the corner.

I would imagine the extra stress on the adjacent bolts would soon cause them to fail. I generally do not drive hard so I could imagine adjacent bolts lasting for some time but eventually the next bolts will go.

I am wondering if only one fail, will it result in slow coolant loss which is something I can monitor by checking it it weekly?

Cheaper for MBZ than doing the pro-active/goodwill route. If the cost is $3k-$4k, then the aftermarket route with the ARP bolts would be the better choice. James from ACG quoted 15 hrs to R&R them. Wonder why no-one has jumped on a class-action since this, at the moment, seems more prevalent than the cam wear issue based on reported failures to date.

I check oil level weekly by dipstick. I check coolant levels every 3-4 months. Try as I might I don't think that behavior will change...nor for me, should it. But if I had to guess I'd say that multiple bolt failures would quickly follow the failure of the first (single) bolt.

single bolt failure will result in pressure release from all other bolts, given that there will be an outlet at one location, and therefore not necessarily cause all others to fail. All it takes is one to fail which will result in hydrolock...all it takes is one, and coolant release, resulting in serious damage...

We also need to compile mileage statistics at time of failure.

Thanks Merc63.

I was talking with an mb tech on friday and he told me that they are always replacing the head bolts on the C63! This now has me very concerned. I have 3+ years/60000kms left on the warranty and am wondering if I should do some preventative maintenance (i.e. upgrade the head bolts). Do you think the dealer would pay for the change or will I have to wait for them to fail....

I haven't been on the forums for a long time since I sold my E63 quite a while ago. But the other day I saw my SA (who is also my Porsche SA; same dealership.) He told me about the TSB and that it applies to a serial number range of motors. It covers day one to early 2010. He couldn't give me a copy because he said MB doesn't want it floating around. But it is on STAR TekInfo, so anybody can get it.

And apparently if I still owned my car, the 'solution' would be to have a CEL and coolant loss 'happen' right before the warranty is up. Then the new head bolts would be installed. I have had a very positive and long time relationship with my dealer. I'm assuming you get the drift here. ;)

Here is an E63 with a blown engine due to failed head bolt(s) from last year: https://mbworld.org/forums/w211-amg/...ne-09-e63.html It was an '09 E63 with 26k miles and another failed one from another poster near the end of the thread.

As I mentioned, if you have a good relationship with your SA and your dealership, then 'arrange' to have coolant loss and a CEL before the warranty is up. The combo of coolant loss and CEL is the criteria for the new head bolts to be installed under warranty. :y

That said, I have a feeling that in the long run MBUSA will do after warranty fixes for this issue since it's now well known and they are fully aware of it.

I'm doing another set right now on a CL63. The bolt doesn't have to fail for there to be an issue. The most common way I've seen the issue manifest itself is slow coolant loss. The heart of the problem is the bolt head design. The original bolt heads that fail are a torx head design. This creates a thin cross sectional area between the bottom of the torx where the socket goes to tighten the bolt and the shoulder of the bolt. The new bolts are inverted torx which are. Much thicker. I'll take some pics tomorrow and post them here. If your car is in the Vegas area and has the issue I'll take care of it for you.

"Has the issue"...I assume you mean the slow coolant loss, yes?