Plug hole Dirty or Stripped?

Guys,

I just changed the spark plugs in my friends 2000 XJ, everything went fine I thought, then we turned it on and heard a clicking leak type noise. I had a suspicion that it was the # 1 spark plug, so I took it out, looked at it, seemed ok, and tried to put it back in. Got maybe 1 turn out of it before it caught. Pull it out again, and this time it was definatly eating at the threads on the plug. It wasn't forced when I put it in in the 1st place, and the old one certainly came out fine, so WTF? Is it easy to strip the threads on the plug holes? I wouldn't think not since it's iron. Anyway, I put the plug back in till it caught and my buddy made it home OK, but god damn am I mad right now. It seems every friggin time I touch his jeep something goes wrong, which isn't me, I'm pretty damn good at this stuff.

Anyway, please chime in, I have to fix this tomorrow at lunch. Should I chase it, tap it, or pour gasoline on it and light a match? :explosion

Also if anyone knows the size/ pitch that would be great.

Thanks,

Todd

The spark plugs answer to some standard thread - the two automotive sizes are M14 and M18. I don't recall the pitch, but we've got M14 plugs, and a chaser for M14 spark plug threads will work fine (just go to the parts house for one.)

TIP - if you are going to chase the threads, buy some greae when you get the chaser. Pack the flutes with grease, and only go about 3-4 turns at a time. Each time, pull the chaser, clean the thing, and put new grease on it.

Why grease? Because, if you loosen any chips, they'll get caught in the grease. Better that than they got caught in the piston rings...

If the chaser doesn't work, you're probably looking at a Heli-Coil or some other insert, and that will be a little more involved (it can be done without pulling the head, but get someone that knows what they're about to help you if you haven't done it before...)

5-90

Well reading what I said initally, do you think that the hole could be stripped, or is it salvagable?

Well, I keep chasers and inserts around as a matter of course - since my two boys seem to like cars with aluminum heads (I don't know why...)

Go ahead and try the chaser - it's 10 minutes' work, it's a cheap solution, and if it fixes it, groovy. Iron heads are pretty tough, but plugs have steel sleeves for the threads. If it comes to the head or the plug, the plug's gonna win, and there's not a lot you can do about it (I used to just put Heli-Coils into aluminum heads automatically when building performance engines - and not just in the plug holes...)

The chaser and grease will probably run you about $10-15, and if it fixes it, you're just ducky. Remember - a chaser is NOT A TAP! It's not designed to cut threads, just to correct malformed ones. Therefore, you shouldn't get a lot of chips, but it's a possibility - I've seen it before, and that's why I suggested the grease.

Anyhow, try the chaser and put the plug back in - if you can get five or so threads to bite, you should be golden. If not, make arrangements to install a Heli-Coil - it can be done in the driveway, but you'd better have some idea what you're doing (and the kit is rather spendy, so that's another reason to try the chaser first.)

Without actually seeing the hole myself, I couldn't really tell you what's going on in there - and I don't like to guess...

5-90

Sounds like the plug did'nt seat. Pull the plug and use a flashlight to look into the empty bore, hopefully its only grime that fouled the threads up. If you did cross-thread it youll see it right away. The head itself is harder steel than the plug, the plug usually galls first and leaves metal debris/plating in the threads of the bore. All may not be lost. (If you didn't torque the shit out it that is!)

You can subtly feel the threads line up in the taper as you start, it can take a while to feel it line up. Make sure you oil the plug's threads first and be very cautious, if it hangs up, rotate it opposite and then back again like your retapping.

So I ran and got the thread chaser this morning, $6, not bad. I'll be trying this at lunch to see if we can get the plug in more. Oddly the jeep runs fine, but makes a clicking vacuum leak noise which is annoying. I'll let everyone know how it goes.

The Chaser worked perfectly, all fixed now. Thanks everyone for your help.

I only use my finger to start plugs or at most spark plug socket with short extension and then my fingers, I *feel* it start, if I feel ANY binding I back off and rotate backwards then try again. I also found a 2" long piece of vac hose over the end of the plug works well to, you can still *feel* it go in...

Yep - and for final tightening, I use three fingers and a "flying saucer" ratchet (like a "palm ratchet," only rounder and about 2" across...) for torquing. Since I also use never-seez on the plug threads, it's actually enough.

Funny - my kids used to watch me do it all the time, and it seems like I had to fix a plug hole for them about every other month anyhow. Don't worry - I used to charge them $50 each time I did it, so they did learn. Eventually.

Cheap lesson harshly learned. I made a total of about $400 off of that.

5-90

5-90 said:

Yep - and for final tightening, I use three fingers and a "flying saucer" ratchet (like a "palm ratchet," only rounder and about 2" across...) for torquing. Since I also use never-seez on the plug threads, it's actually enough.

Funny - my kids used to watch me do it all the time, and it seems like I had to fix a plug hole for them about every other month anyhow. Don't worry - I used to charge them $50 each time I did it, so they did learn. Eventually.

Cheap lesson harshly learned. I made a total of about $400 off of that.

5-90

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That's a riot, maybe they'll get better than you one day and charge you money :shocked:

Maybe, but I found that charging them to fix when they made some dumbass mistake motivated them to learn just a little quicker...

Considering they both played hockey (spendy) and constantly got into fights with each other at home, that wasn't my only little money spinner. Besides, I ended up spending most of it back on them anyhow - for school, for gear, for food, or whatever. It all evened out in the end.

5-90

5-90 said:

Maybe, but I found that charging them to fix when they made some dumbass mistake motivated them to learn just a little quicker...

Considering they both played hockey (spendy) and constantly got into fights with each other at home, that wasn't my only little money spinner. Besides, I ended up spending most of it back on them anyhow - for school, for gear, for food, or whatever. It all evened out in the end.

5-90

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Like your style sir!

Thank you.

Consider it was A) a means to make sure their lessons "took" a little quicker, and B) a way to supplement what I spent on them, so I could keep my own hobbies, it came in handy.

5-90