Robin 993DX

I am pretty sure I have one cross threaded spark plug, ironically it is a plug that's right out in the open on the bottom bank easy access.

Don't ask me how, because I swore it was like that from the factory. But can't remember if it could be the stupid me.

Going on almost 90k miles I have not bothered changed it since 30k miles.

The upper plug looks perfect after I removed it recently.

What should I do? I know there are the heathcoil thread thing I can do.... what do you guys suggest?

Crimson Nape Racing

The same thing happened on one of my older 911's. I just used a little extra muscle and let the new plug force its way in. I suppose it cut its own threads like a self tapping screw. Not the "proper" solution, but it worked in that case anyway. After several times, the plug was as easy to replace as any of the others.

Robin 993DX

Yikes! I guess I will leave it in as it is...

amfp

Robin,

I recall reading a response from Joel's @ PCA Q's. Found this in his archieves, fyi:

"It is possible to try re-threading the spark plug in such a way that it would be correctly threaded and oriented, instead of cross-threaded and angled. I would practice on a different one where you aren't having trouble, say #2 next to it. If you can do this by hand, that is, using the socket but not the wrench, then it might be OK. I would oil the spark plug threads lightly first. The risk of course is of getting any shavings into the cylinder. As you feel it starting to thread, immediately back it out and inspect & clean the threads (e.g. wipe off any shvaings with a shop towel that won't shed).

I would expect to repeat this procedure any number of times, counting how many turns you are advancing each time. If you remove and clean it each half turn, or each full turn, you may be able to get this right without much risk of losing shavings into the cylinder. In other words, thread 1/2 turn, remove & clean, thread 1 turn, remove & clean, do 1-1/2, etc."

Jack of Hearts

Agree with previous posts....if it's not too bad you can usually chase out the hole. One method I've seen (but never used) is to take a hacksaw and cut a slot in an old plug, so it is more like a tap, then gently thread it in, a small amount at a time (as Reiser suggests). After you have the threads serviceable, you can attach a small pipe to your shop vac and vacuum out the cylinder before finally reinstalling the plug.

But that's all if it's not too bad. How bad is it? How do you know it's cross-threaded?

JoH

PS: I always use a tiny bit of Never Seize on any plug going into an aluminum head.

4sound

Snap On makes a tool that will clean up the threads. Its like a tap, but not as sharp. If there are enough "Threads" left in the head, you should be ok.

Robin 993DX

Well.... for the life of me I couldn't loosen the plug. And I am afraid it will break if I try it too hard.

As far back as I can remember the first time I tried to change that plug it was tight, and went back in the same way. Since then I have not tried to do anything with that plug.

Crimson Nape Racing

chances are it is "just" stuck. I understand not wanting to break the plug. I would try using a few tricks for removing stuck bolts:
1. soak the snot out of it with liquid wrench or something like it and tap the plug (gently) with a hammer to work the liquid wrench into the threads.
2. heat the plug w/a propane torch.

I am far from an expert, but I have never heard of plug breaking off in the head. I would try #1 above with a big ol honkin breaker bar on your wrench. You'll probably break the socket before the plug.

John H

Isn't there a DIY on p-car.com for this?

Porscheaddiction

I have had it happen to me luckily the plug snapped just as it began to loosen. I was using a breaker bar btw. Now every spark plug change I make sure I use anti
seiz.
Chris

Red rooster

Could be worth taking the car for a drive before trying to get this plug out .
A bit of temperature in the head will help -aluminum expands more than steel .
The slot in an old plug is a good idea. Used that one myself and it works !!

Good luck

Geoff

Robin 993DX

Thanks for all the good advice...

So assuming I try to get this plug out and then it:

(1). Snaped... What then?
(2). I pulled all the threads out and there is no way to get a new plug to thread in... What then?

Just want to evaluate all of my worst case alternative before I proceed.

Jack Esposito

Usually when you snap a plug off, it is the porcelain piece that breaks not the metal hex attached to the threads.
The trick to getting the plug to thread back in correctly is getting the plug aligned square to the hole. If you machine a few threads off the end of the plug, that will allow the plug to drop into the hole for better alignment before you start turning into the threads.
I had to fight with one of my plugs to get it aligned properly. Luckily I hadn't threaded it in much before I realized it was cross threaded.

Good Luck

Jack

sonny1

Robin, start by unscrewing a little at a time, then screw back it in, it takes patience but it will bulge, then go buy a spark plug thread chaser, there are different kinds, preferably the ones with smaller outside diameter on the main body so it will fit easely in the head bore, and start chasing the thread, make sure you have it as straight as posible,lubricate the threads with cutting oil while you are taping it.,you should be out of the woods soon.,I know I have been there lots of times,btdt,cheers! Sonny.

Red rooster

Be careful!! A really jammed plug will snap just below the socket hex . Then its head off and a pantomime getting the rest out !
My suggestion of getting the motor hot was not a theoretical idea !! Its amazing what a difference a few degrees can make .
Big thing , as has been said , is too go at this slow . Once it gets moving you are on the way but still dont rush !!

This is a PIA.Good luck

Geoff