I took my car in for a routine annual service at a local garage. During the service, a piece of debris from a broken spark plug fell into the engine. The garage says it was 'just one of those things' that could not be prevented, and I have to pay for the cost of repair (including sending the head away to a specialist). Is this right - ie is it really the case that reasonable care on their part could not have prevented this happening?

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    I think it comes down to what it's reasonable to expect. So my question is - should a competent mechanic be able to change a spark plug without getting debris in the combustion chamber, or is it possible that some debris would fall in even though they took all reasonable precautions? – David Williams Sep 8 '17 at 19:20
  • Sounds unusual ;However, I have had 2 platinum center electrodes fall out of 2 Bosch plugs in one engine. Fortunately , as far as I know they did not do any damage. – blacksmith37 Sep 8 '17 at 21:27
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    Thank you, Blacksmith. I believe it was a bit of the ceramic insulation that broke off and fell into the combustion chamber. Surely that should be avoidable? – David Williams Sep 8 '17 at 22:37
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    What kind of car is it and was the engine run? – Ben Sep 9 '17 at 1:55
  • It's a Ford Focus 1.6 Titanium. After looking for the piece of debris, they couldn't find it and thought perhaps it had dropped on the floor and got lost. They road tested the car, and returned it to me. I drove it about 5 miles and then the engine warning light came on. The engine was also sounding not right - I guess mis-firing. They now want to strip it down to get deeper in to find the debris, and repair any damage. – David Williams Sep 9 '17 at 8:09

Usually, reputable garages would in these kinds of circumstances pay for the accident. However, reputable garages have a higher labor rate than non-reputable garages, so you get what you pay for. I would first try to negotiate with the garage, then find out about the consumer protection laws in your country if that doesn't help.

About sending the head to a specialist: I don't believe there's any reason to do that if there's no reason to suspect the head is bad. I presume the idea is that if the head is removed from the engine, it's a good opportunity to test if it is good, but considering you didn't require a typical repair of a damaged head gasket, there should be no reason to suspect the head is bad. How much did the specialist service cost, and what percentage it was of the final price? I probably would have omitted this specialist step if all that happened was just a broken piece of spark plug in the engine.

  • Great comprehensive answer. +1 – Pᴀᴜʟsᴛᴇʀ2 Sep 8 '17 at 17:15
  • Thank you, that's helpful. They are a small, but well regarded local garage. It's interesting that you say that the head repair is not necessary. I've no reason to believe it was not 100% fine when it came into their hands! – David Williams Sep 8 '17 at 17:34
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    From a consumer protection point of view, I think it comes down to whether the garage acted to the standard of a competent professional. Should a competent professional be able to avoid this problem (ie not drop debris into the engine, and then run the engine), or is it simply impossible to ensure that no such debris gets into the combustion chamber even if you take all reasonable care? – David Williams Sep 9 '17 at 8:21

Not an answer per se; but in similar situations I've had great luck putting the contaminated cylinder to BDC by hand, filling up the cylinder with foamy shaving cream, and then adapting a shop vac nozzle to fit over the spark plug hole.

Somebody holds the shop vac in place while somebody else cranks the cylinder back to TDC slowly by hand - mindful of any binding.

I have a borescope to inspect the success, but if you didn't you can sift through the vacuum canister to verify the offending contamination was removed.

My "answer" would consist of no, that's perfectly avoidable by any competent mechanic. And certainly should have been rectified at no cost to the customer. A proper spark plug socket would not let any insulator pieces fall out past the socket and into the cylinder.

  • Thanks guys. I'm afraid my unfamiliarity with this site means that I have probably not used it properly; but thank you all for your help. @juhist – David Williams Sep 12 '17 at 10:05
  • Some Mustangs came with only ceramic connecting the treaded portion to the hex portion. These tended to break leaving the threaded portion in the plug bore. There are workarounds for this. – TomO Sep 12 '17 at 21:30

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