Mercedes-Benz Forum banner

2006 ML 350 w/ a hole in the #6 piston?!

4K views 20 replies 9 participants last post by  MB-SV 
#1 ·
Yup, you read it right a hole in the piston. Has any one ever heard of this sweetheart of a problem? At 107000 while driving at posted highway speeds we felt a sudden stream of misses. After some diagnoses the hole in the #6 piston was found with a bore scope. Of course it's out of warranty, so now what?
I'm just digging to see if any more experienced benz owners have heard of or would accept such a problem?

By the way, always Mobile 1 full synthetic, MB plugs, routine changes, etc. It did have the seemingly normal balance shaft issue and replacement about 40k miles ago.

Thanks,
n8
 
#2 ·
That really sucks...
Makes you wonder if these things are designed to fail around 100K miles forcing you to trade in and buy again??

In my day, the only time I ever melted a piston is when I had the wrong timing, or not enough fuel for proper combustion. Usually when I was trying to squeeze 300 turbo hp from a 2.0 VW Golf twin cam motor.:D (Got 258hp to the wheels eventually)

Bore scope your other cylinders and see if they show signs of detonation, or check the spark plugs for detonation issues. You will probably see they were hot also, and #6 just was the weakest link. Fault has to be in timing control, maybe an error in the famous cam sensor?
Doubt you were spraying NOS, added boost or were using a stand alone ECU, so the factory tune that ran for 100+K miles is proven. Only area for error then is an input error, so my gut says cam or crank sensor.

Either way, you wont like the prices to repair or replace the engine especially since they have the nice shiny new turbo 2012 ML550's on the lots. Sure they will happily take yours as a trade plus less ca$h than you will need for the repair as a down payment.
 
#3 ·
Sorry to hear this. I have not heard any piston issues with the ml350 engine. That same engine is used in most the Mercedes models over the years and besides the balance shaft issue, I have not read too much bad press on this engine. Unfortunetly you may have had one of those "fluke" incidences. Unless something was done wrong back when the balance shaft was replaced and it finally showed. Best of luck. I'm sure there are many used engines avail for a swap.
 
#4 ·
Not heard of this problem, plenty of other problems with 2006 ML350 that are less severe.
 
#5 ·
The 06 ML500 I had was flawless.Not one issue during 4 years of ownership! Don't be so quick to discuss problems unless you have experienced them. As for this piston problem has the OP had this vehicle since new?? This is the type of issue that can be caused by lower than suggested octane fuel. Perhaps the OP or the previous owner if there was one used lower than reccommended octane fuel on a regular basis and the preignition (knock) did this damage. Other than that it could be a manufacturing defect. Perhaps MB will step in even if its beyond warranty.
 
#13 ·
I have a '07 ML320 cdi with 135000 miles. Can anyone tell me what is the function of the fuel rail what it controls and how come when it fails it could also cause some other electronics ie NAV to stop functioning for a short period.
FYI when the car stalled out previously I thought I was having vapor lock issues but was told I needed a new electronic harness.


Sent from my Autoguide iPad app
 
#14 ·
Back on topic

Thanks for all the input from everyone. Since starting this post I've gathered that no one else has had a similar hole in the piston problem, but other problems have emerged that are also frustrating. I can say that while I've owned the ML I've only used the highest octane available. I never noticed a decrease in performance, engine lag, or any symptom at all previous to the sudden stream of what felt like misses on the highway which lead to the discovery of the hole in the piston. So, my choices for moving forward are limited and perhaps you all have some opinions.

My ML has 107k on it. So do I:

1) Replace w/ MB engine, about $11k?
2) Replace w/ salvaged engine, about $7500?
3) Trade in and move on w/ the dealership buying it ($6k) and MB chipping in some ($2k) towards the price of a NEW MB?

Finally, does anyone have any advice on talking w/ and dealing w/ MB beyond the dealership? So far they seem untouchable.

Thanks for sharing your knowledge.
 
#18 ·
Thanks for all the input from everyone. Since starting this post I've gathered that no one else has had a similar hole in the piston problem, but other problems have emerged that are also frustrating. I can say that while I've owned the ML I've only used the highest octane available. I never noticed a decrease in performance, engine lag, or any symptom at all previous to the sudden stream of what felt like misses on the highway which lead to the discovery of the hole in the piston. So, my choices for moving forward are limited and perhaps you all have some opinions.

My ML has 107k on it. So do I:

1) Replace w/ MB engine, about $11k?
2) Replace w/ salvaged engine, about $7500?
3) Trade in and move on w/ the dealership buying it ($6k) and MB chipping in some ($2k) towards the price of a NEW MB?

Finally, does anyone have any advice on talking w/ and dealing w/ MB beyond the dealership? So far they seem untouchable.

Thanks for sharing your knowledge.
You say you have used the highest octane available. Was it always over 91 octane? Seems that you purchased the vehicle as a preowned. There is really no way to determine what the previous owner did with regard to fuel. In regards to your actual question, my take is to trade for a new one and between the dealer and MB I would think you could negotiate a better than $2000 chipping in. Try to get a face to face meeting with the area rep for a start.
 
#15 ·
I would trade to a new model, and use the $7500 you were going to spend on an used engine + $6000 trade value + MB's $2000 "chipping in" as a down payment. Then you have a new with warranty W166 model. And these new ones have a redesigned 302 HP GDI engine. (Whether that's for good or bad.)
Still a sucky situation as you would expect MB engines to not have this issue.
Hopefully yours was a one off fluke.

I have seen posts where MB Corporate was a joy to work with, or a nightmare of uncaring snobs. Mostly seems that when you are within warranty, they will do whatever to make you whole.
 
#19 ·
Thanks again for the replies everyone, I really appreciate the feedback. So yeah, I'm leaning towards the trade in but I'm not quite there yet. I need to get all my numbers in line and making sense before I agree to continue to pay MB month after month. SOSH, you're right on with your question and I've thought about that. My position is that I bought a CPO vehicle that carries a legacy and certain expectation to perform for a lot longer than 107k. I know that the fuel I put in it was always 91 octane or better, always. I'd like to assume that if MB CPO'd it, they were comfortable with it's condition at that time. That's why I'm thinkin' it's a fluke, phantom metal fatigue, something extraordinary!
Again, thanks for the feedback. I'm only hoping to learn from other's experiences and share mine here. Man I hope no one else has this hole in the piston problem though!!!
 
#20 ·
Resolution (ish)

All,

So over two years since the onset of this endeavor. I thought I'd share what I've learned in case others have reports of a similar issue.

Here's the skinny; what was thought to be a "hole in the #6 piston" is now speculated to have been carbon (the dark circle looking hole thing) in a field of shinny metal on the piston head. By the way, the bore scoping and the report of a probable hole in the piston came from a popular certified MB dealer / garage here in the Fox Valley of Wisconsin.

The truck sat for nearly a month before I was ready to deal with it, I was moving at the time great fun! When starting and driving for the first time in nearly a month it ran fine! Weird. Continued driving produced a few more periods of misfires and bent spark plug electrodes, but pulling the plug and re-gaping fixed the problem.

I still have the truck and my wife drives it daily!

After discussions and head scratching sessions with my local MB service tech, he made a simple and I think very appropriate suggestion. Low grade fuel with ethanol may be to blame for the build up of carbon on the piston, and once I began running higher octane fuel without ethanol the carbon gets released and bangs up the spark plug finally getting lodged in the valve. He thinks a chunk of carbon released and wedged the exhaust valve open. So when the MB garage did a compression test, it was low and the dark carbon to a grainy bore scope camera looks like a hole!

The woman I bought the truck from said she had to sell it because she could not afford the payments. Well when your cash strapped where will you try and save money? Everywhere! Like I say, a simple and logical explanation!

So that's my story. Good luck in your future trouble shooting days!
 
#21 ·
Great followup report, certainly emphasizes importance of using fuel grade recommended by Mercedes. Glad to hear of your successful resolution. Best of luck with the ML.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top