spark plug replacement

I just finished changing mine; thanks to you and everyone else who posted all the encouraging experiences and advice. I used a regular 5/8" deep socket to unscrew the old plug, a magnet to get it out of the well, a piece of 1/4" ID vinyl tubing to get the new one back in and threaded to be ready to torque to spec. Much easier, I think, than trying to maneuver the plug & socket combination, had I used a magnetic or rubber-insert socket. Actual time on the job was around 45 minutes. Next time will be faster .

 

cross threading, bolts snapping....

all this talk has me a little gun-shy on changing the plugs myself!!!

 

That's just beginner's apprehension. Changing the plugs on my Prius was a lot easier than changing the single plug on a pressure washer I've got. I missed all that bad-vibe talk, thank goodness. I can't imagine snapping any bolts involved in this operation, and using something like the rubber-tubing trick to insert the new plug makes cross-threading the plug impossible. If you are at all mechanically ept, go for it.

 

Hi mfa, how many miles did you have on your old plugs before you changed them? I've got a new set of NGK's ready to go here. I was gonna pull them about 100k miles (next service) but I'm thinking of putting it off a little longer, seeing as everything is still running super smooth right now.

I've currently got 99000 miles clocked up. Given that the engine is still running very smoothly, I'm wondering how long I should hold off on this?

 

Some people recommend changing as soon as 60K miles. I did mine at 96,053. The engine ran a little ragged at shutdown, and the old plugs didn't look real great. New plugs look great, but the engine still shudders when it shuts down . It's such an inexpensive maintenance item, I'd tend to take the conservative approach.

Update: I just changed my PCV valve at 124,779 miles, and feel it was overdue. I would seriously consider combining spark plugs and PCV valve changes every 100K miles or so, since they're both hard to get at, and the same amount of vehicle disassembly makes both easy. Spark plugs and PCV valve are about the same cost as well.

 

I completely understand. A while back I tried to unscrew one of the plugs and it just won't move at all. I wouldn't dare to use a breaker bar - afraid of breaking the ceramic or worse. The car had less than 30K miles. I was just curious to see if I could take the plugs out to take a look and maybe add a tiny bit of anti-seize. (Later on there were posts showing the plug manufacturer actually recommended against anti-seize for some plugs.) I gave up eventually.

 

Maybe somebody used a breaker bar to install them . You're not likely to break the ceramic, if the breaker bar is used properly, but there's a lot of "worse" that might happen if you get really unlucky.

 

That's not good, what are you going to do when they need replacing?

If you've got enough room to use one, the best type of breaker bar for plugs is the type where the bar slides so that you can use it as a "T". This allows you to put equal force in either direction and seems to make it a lot less likely to bust anything.

Another tip is to try alternating the torque clockwise/anti-clockwise. Especially with a fixed "T" (non-ratchet) breaker bar.

 

Drive to the dealer, open my wallet, and close my eyes...

 

If it's seized and they have to go to any extreme measures to get it out then they wont hesitate to charge you for it. Most places that do this sort of work know plenty of trick for loosening stubborn parts though. You'd be amazed how much easier something can be after just some relatively mild impacts with the right tool.

For example get a steel tube that will fit over the insulator and contact the metal part of the plug. Tap it firmly firmly a few times with a hammer and then try removing. Repeat as necessary and with a bit of patience it will eventually come.

 

There is nothing wrong with using a 3/8" breaker bar to loosen the spark plugs, applying gradual torque.

What is the worst that can happen? The porcelain tail will snap off. This may happen if you are not using a socket with the rubber cushion insert for spark plugs and the inside of the socket contacts the tail.

So if the tail breaks off, you will need to fish it out with long nose pliers, apply a vacuum or use compressed air to remove any loose particles in the spark plug well, then remove the spark plug metal shell. This is not the end of the world and if you break a plug, you will learn a good lesson in the process and hopefully won't break others in the future.

Cross-threading the spark plug holes in the aluminum head is something you want to avoid at all costs. If this happens then you'll need to seek professional help. This can be avoided by making sure the plug turns easily as you rotate the socket extension by hand, prior to applying the torque wrench for tightening to 13 ft.-lb.

 

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A lot of people get into breaker-bar (or torque wrench) trouble by using an unsupported extension (usually too long) on the socket. The socket has to remain on the plug's axis, with zero offset.

 

Unfortunately, I belong to the group that has broken the porcelain tail of a plug. I was unable to fish or vacuum the piece out, and due to worry that the fragment would score the cylinder during combustion, I towed the car to a garage. They used a scope type device to fish the fragment out.

Not the end of the world, but it made for an expensive spark plug replacement.

 

How did the fragment get into the cylinder? Hard to believe the insulator would break low enough to have pieces fall into the cylinder directly, but I guess it could happen.

 

Hi mfa-prius. My understanding is that he didn't get any fragments into the cylinder, that the fragments were merely in the spark-plug "well", and that the main body of the plug was still firmly in place.

However he couldn't clean these fragments out of the well to his satisfaction, and so was worried that if he continued with the removal he might get some fragments into the cylinder. So that's why he had it towed to the dealer to let them sort it out.

 

Ah; I wondered if that might be the reason. I would have given it a few shots of compressed air, but not everyone has shop air handy... Those wells are pretty deep and not terribly accessible. I wonder just how bad it would be to get some in a cylinder, anyway.

 

Hey guys,

This exercise in buffoonery happened a couple of years ago, so my recollection is suspect. Unlike my understanding of the geometries of a spark plug well and beyond, which is clearly limited. I am under the impression that the plug well ends where the cylinder begins; or put another way, that the tip of the seated plug is in the cylinder. If this is wrong, then my interp of fragment location and dangers is way off.

After I pulled the plug out and saw it was cracked, I was able at first to see the ceramic fragment sitting on a lip in the plug well, but my attempts to retrieve it caused the fragment to fall further into the well, beyond my ability to see. At that point I figured the fragment would be in the cylinder, and be a danger of scratching the cylinder wall as it was blown around during combustion, or get caught up in a valve. Either possibility seemed like a bad idea to chance.

I'm not really sure how I cracked the plug. I was using a 6 inch (I think) extender on my wrench. My recollection is that I tightened rather than loosened the plug initially. I'm probably capable of that sort of error, and I know the other plugs came out without fanfare.

 

102k miles, plugs done.

they smell like burning plastic

 

At 164,000 miles my check engine light came on. A trip to Advance Auto told me it was spark plug change time so I found this thread. It wasn't difficult at all. Besides what's already mentioned, I did move the air filter out of the way. The only issue I ran into was when my spark plug socket wouldn't come out when I installed it. To solve the problem, I just ran a string through the socket and pulled up when I was done.