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$20k engine repair

Old Jan 27, 2022 | 08:51 PM
  #1  
Bart Sloan's Avatar
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G550 2016
$20k engine repair

Hey All,

Bought a used 2016 G550 a few months ago. Engine light came on and I took it to the Mercedes for service. They charged around $1k to diagnose (pressure test to see where a suspected leak is coming from). They then tell me I need to replace the right cylinder head for $20k. (“The valve guides are worn. cylinder 3 exhaust valve, 65% leakage. This is the main reason for the recommendation of the cylinder head replacement​”).

I asked what they think the cause was. They said it could have been because the previous owner removed the resonators. But maybe not. I’ve asked multiple times and they avoid the question as to what else could be the cause.

They’re also quoting 10k to put resonators back in.

I don’t want to fix it until I know the cause, because I imagine it could happen again.

Car is no longer covered by a warranty.

Am I just out of luck here and have to cough up the $30k to fix this. Any ideas for recourse?

We had the car inspected by Mercedes a few months back days after purchase and they didn’t notice the missing resonators, so I’m thinking there’s some negligence there, especially since they first suggested that was the cause (in writing). Another option is that the dealer may be liable because the car wouldn’t have passed a smog check without the resonators.

Dealer gave word that it was inspected but stupidly I don’t have a copy of the report.

If a 5 year old Mercedes engine breaks down are you just out of luck?

Should I screw the Mercedes service techs and find a non Mercedes tech?

Thoughts?


Last edited by Bart Sloan; Jan 27, 2022 at 09:09 PM.
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Old Jan 27, 2022 | 09:11 PM
  #2  
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So sorry to hear your new purchase has the engine problem this early in the ownership.

Definitely find out from other members if there's an Independent Mercedes repair facility who can give you a second opinion.

Also regrading the resonators, I'd say look up the eBay and I am sure you find a used one off the internet.
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Old Jan 27, 2022 | 09:48 PM
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The valve guide wear is not from missing resonators. The resonator increases back pressure (when present) and reduces back pressure when it isn't there as well as changing the sound. None of that will cause abnormal valve-train wear on one cylinder.

The guide wear could be from many things. Like the seller putting a bad head on it and took the good one. Or it could be a defect from the manufacturer. Typically the guides wear more evenly and have close tolerances. What you could do is find a shop to replace the valve guides on #3 and you don't need a new head for that. It is a $5 part with lots of labor hours. Possibly a new valve too, but still cheap comparatively ($50?).

The recommendation for the cylinder head replacement could be because they don't know how to do valve work so they replace the part the valve guide is attached to and that is a massive unnecessary expense. They may also believe the head is machined wrong and for that reason you would need a new head. But don't suggest the head was machined wrong because they'll just say yes, that is it.

Last edited by hard top; Jan 27, 2022 at 09:51 PM.
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Old Jan 27, 2022 | 09:58 PM
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I think the dealer sticking it to you right up the bum with an extremely large jar of Vaseline. Find a really good Indy mechanic who has access to a good engine machine shop and save yourself a boatload of cash.

As for the resonators being the cause, higher the normal exhaust rates/temperatures can burn valves, but it seems to me that removing the resonators should not push things to that point, but it may be a weak design. Find a used set somewhere or find a good aftermarket alternative exhaust.

As for smog, in general, it depends on what state. In general, for Federal emissions, anything from the second O2 sensor back is usually okay, but for California and like states, it may be an issue.

Last edited by Floobydust; Jan 28, 2022 at 06:22 PM.
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Old Jan 28, 2022 | 07:28 AM
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Originally Posted by Bart Sloan
Hey All,

Bought a used 2016 G550 a few months ago. Engine light came on and I took it to the Mercedes for service. They charged around $1k to diagnose (pressure test to see where a suspected leak is coming from). They then tell me I need to replace the right cylinder head for $20k. (“The valve guides are worn. cylinder 3 exhaust valve, 65% leakage. This is the main reason for the recommendation of the cylinder head replacement​”).

I asked what they think the cause was. They said it could have been because the previous owner removed the resonators. But maybe not. I’ve asked multiple times and they avoid the question as to what else could be the cause.

They’re also quoting 10k to put resonators back in.

I don’t want to fix it until I know the cause, because I imagine it could happen again.

Car is no longer covered by a warranty.

Am I just out of luck here and have to cough up the $30k to fix this. Any ideas for recourse?

We had the car inspected by Mercedes a few months back days after purchase and they didn’t notice the missing resonators, so I’m thinking there’s some negligence there, especially since they first suggested that was the cause (in writing). Another option is that the dealer may be liable because the car wouldn’t have passed a smog check without the resonators.

Dealer gave word that it was inspected but stupidly I don’t have a copy of the report.

If a 5 year old Mercedes engine breaks down are you just out of luck?

Should I screw the Mercedes service techs and find a non Mercedes tech?

Thoughts?
Don't go back to that dealer. $10K for resonators? That's insane. I've heard of catalytic converters costing $4K-$5K to replace, but not the resonators. They are essentially just mufflers, and the decrease in back pressure from having them removed didn't cause your motor issues. Literally millions of vehicles run aftermarket exhausts which reduce back pressure, and there aren't millions of vehicles running into valve issues.

Find an independent shop that can do motor work and have them do a valve job. How many miles are on the truck?
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Old Jan 28, 2022 | 08:01 AM
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Sorry to hear.

Resonators have nothing to do with this. It’s an MB design defect, one of many on the M157/M278 engine.

Search the 166 sections of the site and you will find many posts on valve guides and cylinder scuffing.
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Old Jan 28, 2022 | 10:13 PM
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Some very useful insight in this thread for you, OP.

Also interested in how many miles are on your truck.
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Old Jan 31, 2022 | 10:44 AM
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Not exactly the same situation in terms of engine issues, but maybe a guide in how to proceed.

https://clubgwagen.com/forum/viewtopic.php?f=34&t=19250

Last edited by shiann; Jan 31, 2022 at 01:25 PM.
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Old Mar 18, 2022 | 11:12 AM
  #9  
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My S550

A few small issues during my ownership over 38000 miles...now dynamic seals no longer work.
<Might join the Tesla bandwagen.
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Old Mar 20, 2022 | 10:58 PM
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Originally Posted by autoluke
A few small issues during my ownership over 38000 miles...now dynamic seals no longer work.
<Might join the Tesla bandwagen.

Dynamic Seats?
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Old Mar 21, 2022 | 07:12 AM
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YES/typo Software was reprogrammed last month, and has returned to failure mode.
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