Today: What to Do About Missing Piece?

Dear Car Talk

Dear Car Talk | Nov 05, 2013

Dear Tom and Ray:

I had a spark plug blow out. The tip of the spark plug fell into the engine. Will that hurt it if I can't fish it out? I drained my oil, but it didn't come out, and I am trying to avoid taking the head apart. Thanks for any advice.

-- Stephanie

TOM: Well, like the goldfish my brother once swallowed, these things all come out eventually.

RAY: Actually, are you sure it went into the engine? If the spark plug blew out because it was improperly tightened, the tip also could have blown out. It could have hit the underside of the hood and dropped to the ground.

TOM: That may be why you can't find it -- it isn't in there!

RAY: If you're pretty sure it fell in there, then I'd look for a shop with a borescope. A borescope is just like the thing they used for your last colonoscopy, Stephanie, except it's for cars. It allows the mechanic to snake an optical tube through a small opening -- in this case, the spark-plug hole -- and look inside an otherwise mysterious, dark space.

TOM: If he sees the piece in there, he can try any creative way he can think of to remove it. A magnet won't help you, in this case, because of the particular metals involved.

RAY: But at times, we've been able to remove foreign objects from cylinders using a coat hanger with a blob of silicone adhesive on the end.

TOM: Or sometimes, by blowing compressed air into the cylinder, you can force the piece out.

RAY: But if he can't get it out using whatever tools are at his disposal, then you've got some decisions to make.

TOM: If the piece is clearly metallic, like the electrode, it's likely to do some damage to a valve if you run the car. In that case, it makes sense to remove the head and get the thing out.

RAY: Right. Otherwise, you'll end up paying to have the head removed AND paying for a valve job.

TOM: If it's something that's small and appears destructible, like a piece of porcelain, then you can start up the car, and let the piston crush it and send the remnants out the tailpipe (see goldfish, above).

RAY: And if you can't find it -- so you aren't even certain what, if anything, is in there -- then you probably need to take a chance and try starting up the car.

TOM: I'd let your mechanic do this. His ear is better-tuned to expensive-sounding engine noises than yours is.

RAY: Right. He's bred to home right in on people who need rebuilds.

TOM: What he'll do, with an assistant, is start the engine. If it sounds normal, then he'll know that either the piece was never in there, or it was something that got quickly chewed up and spit out by the cylinder.

RAY: If it makes loud, frightening noises, he'll shut it off immediately to limit any damage, then he'll run a credit check on you and, if you pass, give you an estimate for some serious engine work.

TOM: Good luck, Stephanie.

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