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2011 Toyota Sienna (3.5L): Spark plug porcelain broke off and fell into a cylinder & scored the walls of the cylinder

We have a 2011 Sienna (~74K miles on it). We bought it as a toyota certified used car about 4 yrs back with 40K miles on it & bought platinum warranty until 100K miles.

A little over a month back, the check engine & VSC lights came on in my Sienna. So, I took it to the dealer to get it checked. The dealer had to take the whole engine apart just to diagnose what happened. Finally, they came back and told us that a small porcelain part of the spark plug in cylinder 5 chipped off & fell into the cylinder, and over time it has scored the walls of the cylinder causing the cylinder to loose compression. To fix it, the dealer says they’ll have to replace the short block in the engine, and it’s going to cost me around $8000. The extended warranty says that spark plugs are not covered, so they are not going to cover the cost of the repair. The car has now been sitting with the dealer for more than a month & I have still not been able to convince them or toyota corporate to pay for the repairs. Very frustrated now!

My question is: does this actually happen? Is it even possible for the porcelain to chip off from the spark plug & fall into the cylinder? What are my options?


A manufacturer purchases components such as spark plugs from a vendor/supplier.

If that spark plug fails, and causes damage to the engine while the engine is under warranty, it’s not covered because the engine itself didn’t fail.

Your best bet is to find a used engine from a wrecked vehicle.


Assuming that the spark plug piece was the only loose part found in the cylinder and assuming that your copy of the warranty does make clear that spark plugs aren’t covered, then I think you’re stuck here. The used engine suggestion is probably the best way to go. You could price having the work done by a good local mechanic (if you trust them to do work of this magnitude), but possibly the dealer will cut you a break on the diagnostic charges if they finish the work.

When extended warranties are discussed here (and usually discouraged), it’s often pointed out that they have many exclusions that can come back to bite you. Unfortunately this appears to be a good example of that.

I wonder if something caused the porcelain on the tip of the spark plug to crack. I had the problem on a 1990 Ford Aerostar. I had a misfire that was traced to a spark plug with a broken spark plug porcelain tip. The plug was replaced, but in the backyard with of mind, I had the thought that something had caused the porcelain to break. I was right. I began having problems 6 months later. When the engine was torn down, there was a hairline crack in the cylinder head. Enough coolant hitting the spark plug caused the porcelain to break. My engine was replaced under warranty. I would have the mechanic check the head for a hairline crack. The magnaflux method might reveal this hairline crack in the cylinder head. If this is the case, the engine should be replaced under warranty. Ironically, my present vehicle is a 2011 Sienna.


have the plugs been replaced since you bought the van? What brand of plugs were they? If they have been replaced who did the work?

lion9car - thanks! Yes, I was more concerned about whether this kind of a thing does actually happen, or if the dealer’s diagnosis is incorrect.

Triedaq - thanks for the great answer! I am going to go and ask that question to the dealer. That is certainly a possibility given that this did not happen while anyone was replacing the spark plug (@Rod_Knox the spark plugs are original toyota parts - never been changed given that the first required replacement of spark plugs for a 2011 Sienna is at 120K miles). It sounds strange to me that the spark plug would just crack voluntarily.

I’ve never had that happen to me before, but it seems like it is definitely possible. Infrequent thing to happen for sure, but possible. A spark plug sort of starts out as a hollow bolt, and then the hollow part is filled with a high temperature ceramic insulator material. It has to be made that way b/c the spark voltage is so high and the temperature & pressure inside the cylinder so extreme using anything else would either allow the spark to short out or melt.

Guesses for possible reasons for a failure such as this

  • manufacturing defect – unlikely as parts are closely inspected.
  • damaged during shipping – possible, but the plugs are usually visually inspected by the mechanic to check for such a problem
  • damaged during install – possible, more likely than either of the above
  • damaged while in use – possible, esp if coolant was spraying on the plug due to a head gasket problem or if the engine was pinging due to an ignition timing problem, faulty ping sensor, use of wrong octane of gas, bad gas, or the cylinders were carbonized causing pre-ignition.

Sorry, I know this doesn’t address your actual question, but hopefully provides some ideas at least. Absent evidence from indepent inspection of the plug that failed, I think you’re best bet is to accept you’ve had an unexpected engine malfunction for which nothing can be done, and move on from that. You might ask what they think about simply rebuilding only that one cylinder rather than the entire engine.

Let’s clarify some things, please

You bought this car from a Toyota dealer?

It was certified by Toyota, not somebody else?

You purchased a genuine Toyota extended warranty?

I asked that last one because, believe it or not, service writers and salesmen will also sell you an aftermarket extended warranty. It may sound strange, but I’ve seen it happen

Yes, bought a Toyota Certified used car, from a Toyota dealer with Toyota Extracare platinum warranty.

In that case, I believe they are trying to play a BS game, and are hoping you will go along

I would expect this from some shady aftermarket extended warranty company, who typically sell products that aren’t worth the paper they’re printed on

Were it my van, I would fight it tooth and nail

Bottom line . . . you bought the certified used Toyota from the dealer, even went so far as buying the factory warranty from them, and Toyota and the dealer won’t stand behind the product

I urge you to call BS

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I think you’re stuck on this and I agree with Tester; the best option is to find a low miles engine.

For future reference, it would be a good idea to change spark plug much earlier than 120 or so K miles.

Age and miles can sometimes cause a plug to fail. There’s also the possibility of an EGR system fault which could have contributed to the plug failure.

Personally, I’m of the opinion they should cover this but many extended warranties are made for squabbling over.

“age and miles can sometimes cause a plug to fail”

Let’s put things in perspective . . . OP’s van is 6 years old with 74K. Not that old, not that many miles. Not due for plug replacement by mileage OR time, according to op

“many extended warranties are made for squabbling over.”

Agreed . . . but OP bought the genuine Toyota factory extended warranty, from the dealer

IMO this BS scenario shouldn’t even have played out in the first place. In effect, it means Toyota’s factory extended warranties are akin to toilet paper

I’m fairly certain this van doesn’t have EGR

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I won’t do anything until Bob Moore’s COO, Customer Service Girl or the Mazda GM contacts me to contribute financially to the problem they helped create.

For pete’s sake Kevin your on the wrong thread.


Look, Toyota buys lots of parts from contract suppliers, assembles them into engines, and sells them with warranties. Does Toyota make its own gaskets, oilseals, water pumps, radiators, piston rings, fuel injectors, etc.? Maybe some of those things, but not every one. For them to try and say that spark plugs are a wear item and not covered might be true if the spark plug was worn out, but it is not. It is broken, and the owner did not break it, nor did any unauthorized service break it. It was not supposed to need service yet, so it was not negligence that caused this problem. For them to try and run from responsibility is just plan BS, and the owner should take this to the regional office of Toyota and to the fraud section of the State agency that licenses car dealers, too.


That Toyota dealer and the warranty administrator are apparently trying to use the “Weasel clause” :frowning:


Don’t know if this might help, but how do the dealer and Toyota know WHEN the porcelain chip (or chips) fell off?
Could it have occurred during the original warranty period but was not detected until later (during the extended period with the different terms)? If so, it can be argued that the original warranty (including the 5 year powertrain warranty) should have covered it.
5 years on a 2011 car just expired, and your ~8000 miles per year driving can be compared against the amount of scoring to estimate when the original fault occurred.

@tpruthi, you might contact Toyota directly and explain the situation to them. Given that this is a CPO van, they might be willing to pay for the repair. If you don’t get satisfaction from the first person you talk to, and I doubt you will, ask to speak to the supervisor. If i was in this situation, I would explain that I bought the van because I was impressed with Toyota reliability and customer care, and bought the CPO to get the added assurance that Toyota checked everything to make sure there would be many thousands of miles without problems. That might work, and I’d bet it’s true. If you don’t get satisfaction, ask for the name and address of the next person up the food chain and send them a letter explaining the issue in full detail. If you still don’t get the repair free, get the name of the next person up the line and continue until you get to the president of Toyota America. Attach a copy of each pervious letter, and copy every previous person in the letter chain. I’ve heard this actually works sometimes. Best of luck, and don’t give up yet. Toyota is a huge company and it seems to me that they should provide relief in situations like this even though they may technically not have to. Just because they can act like Takata doesn’t mean they should.


Another idea, if OP has no valid claim due to the used car warranty wording, maybe there’s still some kind of valid claim based on the spark plug manufacturer’s warranty?

I have doubts the spark plug debris caused scoring of the cylinder, It is possible, but I think there are other issues. Previous overheating, coked or broken piston rings, running too lean due to bad injector come to mind.

You have a fight on your hands, sucks you have to fight this for
"bought platinum warranty until 100K miles." and spark plug is not covered.

Second Party or dealer warranty?