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Cracked piston on 2017 c300 coupe

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by Honey, May 22, 2020.

  1. Honey

    Honey Member

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    Hi, My 2017 Mercedes C300 coupe broke down recently. Started to jerk and lose power and white smoke was coming out the exhaust pipes. So I had it towed to the dealership. This is what they said

    "Mercedes"-Hey Honey, so looks like your probably going to need a new engine!! Still confirming but looks like one of the pistons cracked. You're under warranty so its totally covered. I should know for sure in the next day or 2 but plan on keeping that loan car for awhile, may be a couple weeks

    "Mercedes"-Honey just wanted to give you an update. It turns out they don't have to replace the whole engine. They are replacing the turbocharger and they have to replace one of the the pistons.

    "Honey"-Hi Dan, thank you for contacting me. To be honest I do not feel confident in that repair. What kind of warranty is Mercedes willing to put on the engine once the repair is performed. There could be underlining problems as a result of that day when the car broke down. After some research and speaking with the other service centers "SD Mercedes, MB El Cajon" I would feel more confident and safe to have that engine replaced. (MB El Cajon said they are replacing one of those engine a week ).

    "Mercedes"- I understand but nothing is wrong with the engine. We replaced the engines sometimes as well but in this case there is no damage to the cylinder sidewalls so there is no need to replace the whole engine, only the piston was cracked. That does cause underlying damage to the turbocharger as well which is why we are replacing that too. Unfortunately mercedes makes dealerships prove every warranty repair we do is needed so they will only allow us to replace what is damaged. The warranty is the same 4 year 50,000 warranty that came with the car at time of purchase, no extension or anything when a warranty repair is done :(

    "Mercedes"- Basically one of the pistons cracked, which is why you had so much smoke the oil got through and it was burning oil. So we inspected for any damage in the engine, there was no other damage other than the piston being cracked. We replaced the piston then also the turbo charger and the catalytic converter due to all the smoke and burning oil. Refilled all the fluids and everything then test drove and all is good. The technician has his report on the paperwork as well with much more details on what he did (little over my head lol).


    What should I do? Should I be getting a new engine since that is the remedy at other mercedes service centers?
    Thank you
     
  2. John Laidlaw

    John Laidlaw Senior Member

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    Welcome Honey
    usually over there you have more power over MB than we do!
    For me, provided you get the car back with all this work done and its working, you're no worse off than you were before the failure so I'd personally accept. If anything goes wrong throughout the remainder of your warranty you'll get it rectified anyway.
    On that subject is it a 3 year warranty you have? If so, for sure extending it is the right thing to do, that might be a negotiating point - discounted extended warranty?
     
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  3. OP
    Honey

    Honey Member

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    Thank you, I am worried that the car may have a problem down the road as a result of the engine failing and then me be out of my warranty because I only have 1000 miles until it expires
     
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  4. bembo449

    bembo449 Senior Member

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    Think i agree with john on this but id request the warranty on the engine start again and not just run to the end of the original warranty
     
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  5. ajlsl600

    ajlsl600 Senior Member

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    Think as said. But get the warranty extended by them. Or failing all else you. There is a good chance that's the end of the matter. I would want a Detailed account of all work done and why, cause. Then collect info on as many other cases as poss then wait. If work carried out as factory directed. Should be end of the matter..
     
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  6. malcolm210

    malcolm210 Senior Member

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    Welcome! Totally agree with the above, you are between a rock and a hard place on this accepting the repair and negotiating an extension to the warranty is the best way out.
     
    Last edited: May 22, 2020
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  7. LostKiwi

    LostKiwi Senior Member

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    I was under the impression MB warrant parts and repair work for 2 years? I'd push for that.
     
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  8. OP
    Honey

    Honey Member

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    Thank you
     
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  9. OP
    Honey

    Honey Member

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    I will definitely look into that. Thank you
     
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  10. OP
    Honey

    Honey Member

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    Thank you. Who would I negotiate the warranty with? My service advisor?
     
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  11. OP
    Honey

    Honey Member

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  12. OP
    Honey

    Honey Member

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    Thank you. Can you suggest other places I can collect more info?
     
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  13. 00slk

    00slk Senior Member

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    Why did the piston crack? Bad batch, school boy error on assembly plant (dropped piston on the floor, picked it up and carried on fitting it or just real bad luck that one piston failed due to no fault?
    Just thought I would throw a spanner in the works.
    I take it that Mercedes will be crack testing the remaining pistons before reusing them?
     
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  14. LostKiwi

    LostKiwi Senior Member

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    Very good point.
     
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  15. Botus

    Botus Senior Member

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    ...yes, I'd be looking to hunt down other incidences of the piston cracking and how they were treated and if other's played up post repair.

    does it run as nicely as it did ? just as smooth no strange noises or vibrations?

    I guess it must be fairly common or the repair wouldn't have been just the piston.... usually they would just swap the engine over, so I guess it won't be the first one they did like this and they know its OK.

    4 years 50k miles seems odd?
    3 years and 60k miles more usual

    I would get extended Mercedes warranty... even if you have to buy a big service and pay out for the warranty, both together could be £900 but that is still a bargain to get the piece of mind for a further year.... ( you can more or less exchange £ for $ these days)

    other non merc warranties would claim the earlier repair means they aren't paying out.... and a new engine if it did come to that in the next 12k miles would be in the region of 7 to 11 k out of your pocket (so its an utter steal for the piece of mind)

    https://www.mbelcajon.com/new-vehicles/ that's a long way from here...
     
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  16. Botus

    Botus Senior Member

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    you could always chop it in for another.... car's don't last like they used too (and put the warranty costs towards a new toy instead)
     
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  17. malcolm210

    malcolm210 Senior Member

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    Yes, my son pays circa £700 a year for his extended warranty to cover 20k miles pa. I would imagine you will be offered a 1 year warranty on the repair and could pay to extend during your ownership. You may be able to negotiate a better deal no harm in trying, good luck with it and you may be worrying unnecessarily the repair may be fine.
     
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  18. ajlsl600

    ajlsl600 Senior Member

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    Internet, Google, search other forums collect info on any other engine issues like yrs. Keep a file. If yr able to make a decent warranty deal with Benz you may not need to bother.
     
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  19. ajlsl600

    ajlsl600 Senior Member

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    I think benz know about this failure, methinks one piston failure unusual, I have seen this when skirts, pins have cooling jets that block, come loose or even fall out. Does this motor have skirt oil jets and if so pressed or bolted in if failed piston wrecked at skirt cut away would say this the issue if not, faulty Piston, unlikely or coolant circulation in that area of block (soon know)
     
    Last edited: May 22, 2020
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  20. LostKiwi

    LostKiwi Senior Member

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    Apparently (from a quick Google) there is an issue with gudgeon pins knocking in the piston leading to piston failure on the M274 engine.
    Personally if this is true I'd demand all 4 pistons, rods and gudgeon pins be replaced as a minimum.

    The mileages for failures seem to be around 50,000 to 70,000 miles.
     
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