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Discussion Starter · #1 ·
I have a 2015.5 Volvo XC60 T5 FWD model that ran 52k miles. I did my maintenance at a local shop with the spark plug changed this March. And it lost power last week with a check engine light on. I towed the vehicle to dealership and they did a diagnosis saying that the spark plug tip is broken and it may damage engine. Asking 4k to replace the cylinder head and do the further diagnosis. My car has CPO warranty but they refuse to cover the repair since I use a 3rd party ( Bosch 96318) spark plug. They tried to blame the shop who did the maintenance.
I awared that they are scaming for money and asked the shop who changed spark plug to diagnosis the engine problem. The fished a borescope through the spark plug hole and found the piston ring is melting and it scored the cylinder wall. They think it's because of the detonation. Spark plug broken is not the cause but the consequences. Now what need to change is not the cylinder head but the whole engine block.

So here is my question, is that possible that the newly changed spark plug damaged the engine and led to the detonation. Or it's just the engine's issue that lead to the detonation. Both of the party tried to blame the other and the bill of fixing the engine is super high.
 

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I believe this is the proverbial rock and a hard place. I'd say you're unlikely to get the dealership to admit it should be covered without paying for a lot of diagnostic up front. Even then it's a huge risk. They have already made a statement and are unlikely to change their minds in your favor.

I don't know what I would do in that situation. I would start by busting out that CPO paperwork and looking for the exemption they're talking about. Under the Moss-Magnuson Warranty Act I would not think they could void the warranty because you used an aftermarket sparkplug. But someone more knowledgeable (maybe @Tech) can chime in.
 

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You can't see piston rings with a borescope. So while you may want to believe what that shop says, they are not telling the truth.

If you have aftermarket spark plugs that are damaged, the broken parts of the plug likely caused the scoring. Volvo is not going to cover that.
 

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Discussion Starter · #4 ·
Maybe I did not use the correct terminology, they let me see the piston from the borescope, and I did see the piston shape changed due to melting. And I also have the screenshot from their camera. So I believe the detonation happened.
I may guess what lead to the detonation, maybe a badly installed spark plug may lead to it?

128215

You can't see piston rings with a borescope. So while you may want to believe what that shop says, they are not telling the truth.

If you have aftermarket spark plugs that are damaged, the broken parts of the plug likely caused the scoring. Volvo is not going to cover that.
 

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2012 S60 T6 AWD
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I was also inclined to say that you can't see piston rings with a boroscope, but I guess if the engine is that messed up, it's the exception.

Regardless of whether or not the spark plug was the cause or effect, you're out of luck with that dealer. You could probably bring it in for a failed timing belt tensioner (obviously unrelated), and the dealer would probably try their damn best to blame it on the spark plugs as soon as they noticed they weren't OEM. They love to find excuses, and on this one they may actually be right.
 

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I did a couple quick searches of a couple sites and can't find anything saying those plugs are for your vehicle. Are you sure they are correct?
 

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I also agree OP used wrong spark plug.
I used Bosch 9615 Iridium on my 2012 XC60 3.2 and had no issues. Bosch 9615 is also for 2015 XC60.
 

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Discussion Starter · #9 ·
Umm, just double check this is a 2015.5 xc60 with 2.0T 4cylinder Drive-E engine. If that is the case, I think I got some clue for the shop to cover the repair.
 

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Trying to find an aftermarket Sparkplug for the 2.0T motor is very difficult .. the Champion 9412 is one of the only ones i could find listed .. This Champion Plug has a listed heat range of 9
The higher a spark plugs listed heat range, the colder the plug is ..
The Bosch 96318 that was installed in your motor has a listed heat range of 6 .. this is a much hotter plug
Run a plug that is too cold and you will tend to get misfires and fouling of the plug
Run a plug that is too hot and you run the chance of pre-ignition.. the Bosch plug was 3 steps hotter than normal.. in a turbocharged motor it's almost guaranteed that you experienced pre-ignition.
Detonation will cause things like rings to break ... however pre-ignition results in much higher temperature and cylinder pressures and will result in melting of rings and pistons.

Chances are the sparkplug tip did not "break off" .. it melted off

in my opinion, whoever installed the Bosch plugs into your motor should take full responsibility ... Have you removed and inspected the other 3 spark plugs? check the electrodes for signs of overheating or melting..
 

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Discussion Starter · #13 ·
Trying to find an aftermarket Sparkplug for the 2.0T motor is very difficult .. the Champion 9412 is one of the only ones i could find listed .. This Champion Plug has a listed heat range of 9
The higher a spark plugs listed heat range, the colder the plug is ..
The Bosch 96318 that was installed in your motor has a listed heat range of 6 .. this is a much hotter plug
Run a plug that is too cold and you will tend to get misfires and fouling of the plug
Run a plug that is too hot and you run the chance of pre-ignition.. the Bosch plug was 3 steps hotter than normal.. in a turbocharged motor it's almost guaranteed that you experienced pre-ignition.
Detonation will cause things like rings to break ... however pre-ignition results in much higher temperature and cylinder pressures and will result in melting of rings and pistons.

Chances are the sparkplug tip did not "break off" .. it melted off

in my opinion, whoever installed the Bosch plugs into your motor should take full responsibility ... Have you removed and inspected the other 3 spark plugs? check the electrodes for signs of overheating or melting..
Yeah I do see some sort of coating on the other spark plugs and the break one's ceramic also melt down a little bit.
One interesting catch, from this page it seems champion heat range 9 is the same as bosch 6. https://www.boschsparkplugs.net/heat-range-conversion-chart-2
 

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I still can't find anything saying those plugs are for that car. If you put that car in on Autozone's website and look up those plugs, it says they are not for that car.
 

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Discussion Starter · #15 ·
I still can't find anything saying those plugs are for that car. If you put that car in on Autozone's website and look up those plugs, it says they are not for that car.
Thank you so much guys. I will search for more prove and evidence and argue with the shop. Let me know if you find other strong strong evidence.
 

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You should be asking them for evidence. Where did they come up with those plugs for that car?
 

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Thank you so much guys. I will search for more prove and evidence and argue with the shop. Let me know if you find other strong strong evidence.
It should be a pretty easy conversation ... ask the to show you any evidence that the Bosch plugs that were installed in your car are the right application for it .. They will not be able to find it listed .. You can go onto the Bosch website and do a parts search for your motor and it will not come up with a compatible spark plug for it ...

Generally the sparkplug tip temperature between heat range steps is about 100 degrees Celsius ... so going from a 9 to a 6 would show about a 300 degree C hotter tip temp.. more than enough to cause pre-ignition ...

You can easily prove that the wrong part was used on your vehicle.. there is no debating that.. they will not be able to find any documentation that the plug used had an application for your car .. It's up to them to prove to you that the incorrect part did not cause the damage ..

Ask them to install 3 step hotter plugs into their own personal vehicles and drive around with them installed for awhile ..
 

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You should be asking them for evidence. Where did they come up with those plugs for that car?
The Volvo spark plugs are not difficult to find or buy and they're not that expensive. I'm unsure why any shop would use something else.

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