C43 Fun Haver

hopefully I attached that NCU correctly. A little good news for anyone this may apply to if you haven't seen it yet.

PeterUbers

Thanks!

MB18436572

Thanks!!!

jonUF02

How the heck would they even diagnose such a problem from just misfire codes? I wonder if anyone has had this extensive repair done, essentially full replacement of cylinder heads.

C43 Fun Haver

yeah i've seen a few get replaced at my dealer, my ML had the left head replaced due to valve leakage. Tech would check the codes and if it aligns with something head/block related next step is probably a leak test and compression.

rwhyde

The misfire codes is just the first step to determine the rot of the problem. It could simply be an ignition coil or spark plug failure or worn out. Then internal service problem identification will require a compression test and potentially a leak down test to further isolate the problem to an internal failure and whether it is head or piston/cylinder issue. Once they have that data, then they can move to the next step of the major repairs. It is non-trivial to pull a head on these engines.

atxE55K

I went through this in late 2021 and early 2022 on my 2015 ML63. It started with the check engine light coming on and an OBD code for a misfire in cylinder 5. That went on for a month, followed by the car going into limp mode more and more often. I put a new plug and coil pack in cylinder 5 and it did not fix the problem. I was worried that it was an issue with the valve. I took it to the dealer, who completely misdiagnosed the problem. They wanted over $10,000 to fix a bunch of things that I was convinced would not address the primary cause. They refused to do a compression and leak down test. This was incomprehensible to me.

I went to a local M-B independent where they did a compression and leak down test. Turns out cylinder 5 was way out of specification. They recommended pulling the head, which requires pulling the engine. Once the engine was out and the head was off, it was clear that there was an issue with the valve guide, valve, and the valve seat in cylinder 5. This meant a new head from M-B. The shop stayed in close touch and they were very transparent, which was a welcome relief from my experience with the dealer.

Long story short, $20,000 later the car is running great. No CEL, no codes and no limp mode. Hopefully, M-B will do the right thing and cover the cost of my repair.

I will keep you posted.

C43 Fun Haver

Please do keep us posted. That's absurd that the independent shop would not due a leakage or a compression test.. Only thing i could think of is that this engine has do a manual compression and leak down test.. Cannot due that through Xentry in my experience. My cylinder head was replaced under warranty about 2 years/20k ago and cylinder 5 was the culprit... I forget the actually values but compression wasn't horrible, leakage was extreme on the exhaust valve.

atxE55K

It was the MB dealership that would not do a compression or leak down test. I had already replaced spark plug and coil pack on cylinder 5, so I was pretty sure it was the valve issue that others have seen. I mentioned all this to the service writer at the dealership and he still refused to perform the tests.

The independent replaced the fuel injector, which did not fix the problem. Then the independent did the compression and leak down test, and it was clear that cylinder 5 had a problem. Once the cylinder head was removed, it was easy to see that the exhaust valve in cylinder 5 was the problem.

I have never been able to make the Xentry perform a compression test.

C43 Fun Haver

i completely misread your first statement about where the car went first, my bad. Sorry to hear you went through the ringer with the dealership.. Hopefully you get to see any money come back.. doubtful but hopefully..

atxE55K

It turns out that my ML63 was originally purchased in Canada and my local MB dealership said the MBUSA extended warranty does not apply to my vehicle.

Time to check with an MB dealership in Canada.

atxE55K

I reached out to a dealership in Canada and learned that they are aware of the warranty extension for exhaust valve issues with M-B USA. But at this time M-B Canada does not have the same coverage or extension.

Time to reach out to Mercedes-Benz AG and Mercedes-Benz Canada.

byroncheung

Does anyone know if excessive oil consumption would be a symptom of this problem?

atxE55K

It is possible. Does your check engine light frequently come on? Does your vehicle go into limp mode? These are the telltale signs of a bad exhaust valve in cylinder #5. If you have a bad exhaust valve, then oil could be leaking through the valve guide and into the combustion chamber.

byroncheung

A while back it has a CEL and limp mode on and off, which went away after replacing spark plugs and hasn’t come back since. But oil consumption is gradually getting higher and higher now it’s at a qt / 500 miles, makes me wonder if this is the cause.

atxE55K

A compression and a leak down test will answer the question. Start with cylinder #5, which is where this issue occurs most frequently. If cylinder #5 is within spec, then test the remaining cylinders.

BoxMan2008

I test drove a 2015 E63S over the weekend that I am very interested in purchasing. The current owner had the same issue with cylinder #5 at around 83,000 miles on the car. He had an independent shop replace both cylinder heads. I just saw the extended warranty information. I am going to reach out to
him to see if he can hopefully get his money back. The car currently has 87,000 miles on it and runs great.

Are there any recommendations out there on how to avoid this issue from reoccurring? Such as Lucas upper cylinder fuel additive or using a good quality fuel system cleaner every 5,000 miles or so.

atxE55K

I believe (and hope) that the new cylinder heads addressed the underlying valve guide issue.

14’GL63

Bought my wife a used 14’ GL63 with 114k miles a few months ago (Currently has 119k). Previous owner informed me that he would get random #5 cyl misfire codes. After a few trips to the local dealership, they did the compression and leak down tests. MB approved replacing the #2 bank head. They are almost done with the repair and I just got a call from the dealership telling me that MB-USA also approved the #1 head. Score

Rashy55k

Hello All ,

Wondering if this warranty applies to my vehicle? Sorry the PDF was kinda confusing to read but I recently purchased a 2014 E63S with 87k miles with no current warranty that I know of wondering if this will cover if my fears come true Car runs like a bat out of hell only at idle do I feel the slightest hiccups. Car did recently pass smog check here in CA but when I hooked it up to my diagnostic tool it showed a Cylinder 5 misfire but no CEL and a couple days later the code went away also only getting a weird MAF code which was weird to me as I these cars dont have MAF's? Possible vacuum leak causing idle hiccup? so far only replaced coil that seemed to make it a bit better but hiccups at idle are still there. Hoping its a simple fix but after reading the Cylinder 5 horror stories and seeing this post wondering if it will cover my car if worse comes to worse?

Rashy55k

It covers even if you're not the original owner?

BlownV8

Yes,

täglich

@atxE55K, what came of this? Did Mercedes cover your repair?

atxE55K

Mercedes has not yet covered the cost of my repair.

Mercedes USA will only cover the repair for cars purchased in the US. As far as I know, Mercedes Canada has not authorized an extended warranty for this problem.