Rovel

I start to think that M156 head bolt failure rate is really overrated by the internet. I am saying this by reading the thread on this forum where tons of people report high mileage cars with M156 on original bolts, and by looking at the condition of the bolts that I pulled off of my car.


My car is 2007 E63 AMG with 68K miles currently and is well maintained. I expected to see much rustier bolts, but they were just fine with few of them showing some surface rust. I think I could've leave them alone and the engine would survive a long time without replacement too. What do you think?

If you're looking for video DIY I have a video here:

Yuille36

I agree totally with you. This issue is over rated. When I removed my head bolts, they were in great shape with limited surface rust, but nothing that would call for replacing them. Now that I look back, it was a waste of money. But I think that it was cheap insurance, knowing that I wouldn’t have issue in the future. If I had to do this all over again, I’m would just save my money until an issue arose. 😁

cfmistry

Nobody really knows what the failure rate is. Nobody. Not even Mercedes-Benz (since most of the failures are well out of warranty).

As you have read in the thread, there are many early M156s with high mileage on original headbolts. The issue clearly affects a small minority of cars (Certain batch of bolts? Certain assemblers? Poor maintenance? Cars driven hard before warmed up?- my thought).

The consensus for some time has been that they’re NOT worth replacing unless you are a DIY guy with a lot of free time on your hands.

There is a lot of poor information about this topic, from both people who have had failed headbolts and people who have never owned an M156 engine.

insame1

I think the big issue is there is no warning signs. If one fails it cold hang a valve a destroy the engine. There is a reason the 07-09 cars are such a good price. I spoke with my very trusted mechanic about a ppi on an 07 eye and after our conversation I bought an 06 e55.

Rovel

E55 engine is definitely more reliable. When I was shopping around I test drove several E55s and decided to buy E63 which felt like a more refined car overall. However, M156 is not as bad as the internet makes it to be. I think the failure rate is low, and the rate of hydro locked engines is negligible. I think I could've leave my engine alone. I think the internet blew it up because of the way Mercedes Benz handled the cases and treated buyers.

coupesedan

the issue is the failure mode. something like timing chain wear is easy, just wait for the death rattle and replace as necessary.

having a bolt snapped off in the block is an absolute PITA to remove. if you actually manage to hydrolock an engine well that’s on you

Windowguy

I like my E63 a lot. Much more refined and updated than the 2006 E55 that I had.

How does one know if they should go through the expense of replacing the head bolts? I have not read of anyway that you can check except by taking a bolt out. If you do that then you might as well replace them. I got a decent deal on my car and I can do some work like brakes and oil changes on my own but the head bolts are beyond my comfort level. The only maintenance that I can think of that would help would be coolant flushes.

Rob.

Rovel

E63 is the car to be loved, for sure. There is no way to know if the bolts are going to fail or not.

If the bolt does fail, 90% of the time you'll start losing coolant. So check your coolant level often. Note: the level is different when cold vs hot. The tank doesn't have marks, so I added two marks on the tank using sharpie for cold and hot. You can do the same and then check regularly. If you ever start loosing coolant, have a technician check as it could be leaking from somewhere else like hoses. If there is no leak then the mechanic can check the coolant for exhaust fumes. Head bolt replacement after the failure should cost around $2-3K depending on where you live and where you get the job done/parts bought.
The other 10% of possibility is that too much coolant gets inside the engine and hydro locks it.

Like I am showing in my video, I think my bolts were just fine and didn't need to be replaced. There is a thread on this forum where folks with high mileage still have their original bolts. I am just a little paranoid and had to replace them for peace of mind. If you feel the same way, then replacing them one at a time will cost you half the money. In retrospective, I should've not spend the money now and drive and enjoy.

This was the most advanced DIY I undertook and I was nervous. With the help of the forum members and videos, I felt comfortable doing it and documented the process in my video.

Yuille36

Rob, that was my way of mitigating the head bolt issue was to flush my engine coolant every two years, vice every four years. When I finally had the head bolts replaced out of prevention not due to failure. I actually seen that my mitigation strategy had worked as there was minimal corrosion on the head bolts, to the point that my mechanic stated that if it was his car, he wouldn’t change them. But hindsight is 20/20. Had I known that my bolts were in this good shape, I wouldn’t gone thru the expense.

There isn’t a way to check for broken head bolts, other than removing them. One, could remove the ignition coils and spark plugs and then bore scope each cylinder to check for coolant leaks, this could indicate a possible failed head bolt or head gasket.

The only other indicators would be CEL, rough idle, low coolant level, light smoke in the exhaust, or engine failure due to hydro lock 😩.

But keep in mind that there are thousands of M156 equipped AMGs out there that still have original head bolts with no failures.

Some say that the M113K is a better engine with fewer issues, I doubt think. Each engine has its own unique issues, but I personally love the M156 engine, so much in fact that I have owned 2 E63 and 1 C63 with this engine.

My advice would be to put aside some money if your really concerned about this issue.

I’m no longer concerned about this issue with my E63, and have more peace of mind, and a lighter bank account. 😪

Rovel

Update: Tasos Moschatos watched the video and said that in his opinion it was the right time to change the bolts. I trust his wisdom and glad I replaced them. But the bolts didn't really look that much rusty in one looked at them in real life.

tw2

If you aren't replacing them consider more frequent coolant changes. Refreshing the anti-corrosion chemicals will probably go a long way to preventing deterioration in the exposed bolt shafts.

Yuille36

I have been doing this every 2 years, hoping that this procedure would mitigate the issue. And when I finally removed the head bolts, it definitely looks like it has.
After inspecting these head bolts very closely and wiping them done, both my mechanic and I both agreed that we could have left these in, had we had known this ahead of time.
And the bucket lifters looked good as well, with no obvious signs of wear on the cams lubes.

tw2

They look reasonably good. Well you now have piece of mind that it will run forever which I would say would make it well worth it.

SGTzAMG

its a peace of mind. its a hit or miss with early model with M156. not ALL are affected, BUT for some, it will eventually happen.

Just replace them as well as the lifters/tappets; its a huge weight off y our shoulder each time you hit the road knowing that these are good and assure that your engine will be A ok

Rovel

If you have money, or can do it yourself, or can’t get over the thought that it’ll fail, then sure - replace them.

Otherwise, change the coolant often and enjoy the car. Even if it fails, chances are high that you’ll lose coolant and that’ll be the sign.

Like I am showing in my video, I think my bolts weren’t that rusty and wouldn’t fail soon. But if one wants to replace them one at a time proactively, this forum including my another video is very useful.

Yuille36

I changed mine as preventative maintenance, as my car was one of those identified with bad head bolts by engine number. They were replace one at a time, so the entire heads need not come off. I also replaced my bucket lifters with the SLS ones that are graphite coated, and surprisingly enough my lifter noise is gone. 😁. But honestly, even with the added expense, I’m glad that I did it, for peace of mind. I have to say that, this has been my most expensive repair to date. I will say from the data, typically the failures occur after the 90,000 mile mark for early 07 E63 with the identified defective head bolts.

w211E63_Sac

Hi there,
I am about to replace the head bolts on my '07 E63 AMG (M156) engine as well. Did you perform yours? Can someone please look at the parts list that I have?

M156 Updated Headbolt [x20] 156-016-07-69
Actuator Bolts [x4] 910105-012018
Timing Case Bolts [x8] 000000001150
27MM Short Socket for Crank
Mercedes Cam Timing Tool M156 *If you are in Sacramento and have one, I can buy it from you.
Diamond Washers Cam Phaser [x4] ??? (need part number)
Engine Marker - Sharpie
Engine Lubricant - Lubriplate 105
Front cylinder head/timing cover gaskets [2x] 1560162221
Valve cover gaskets [2x] 1560162421
Spark plug gaskets for valve cover [8x] 1560162121
Diamond Washers [4x] 1560510275
What type of silicone to use?

Any other specialty Mercedes tools that I'll be needing?

Also, any advice is welcome!

Yuille36

Since my head bolts were done at my preferred shop, I can't tell you the part numbers. They ordered all the parts that were needed. Sorry.......

M5 LOL

I wouldnt mind LTs/Tuned/ROW E63. The M156 has its issues, but compared to what I see working on BMWs all day they are damn near toyotas LOL. I mean still the E55 is daddy, but the M156 is a lot of fun, its just not faster :wink