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GU8 CRD
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Discussion Starter #1
Hey guys, yesterday when changing the plugs in my tb42e I discovered that the old plug in cyl #2 was only screwed in halfway. Because this is the first time I have changed the plugs since I have owned the car, I don't know how long this plug has been in for, but I'm guessing a couple of years at least.

Of course the new plug won't go past the half way mark either. I stuck a borescope down the hole and I can still see the threads at the bottom of the hole, although they look a bit ratty. Because of the angle of the scope to the threads, I can't really tell if the cause of the half threaded plug is cross threading or something else.

I know a helicoil will work, but I see there are gadgets called “thread chasers” of which there is one type that works from the outside of the hole and another type that works from the inside of the hole. If possible I'd prefer to go the thread chaser route first, but has anyone fixed a similar problem with one of these that can offer an opinion on it's success or otherwise? Ta.
 

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nissan
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Ohhh mate i dont think you can buy them the way you want to......
To do it properly you would need to take the head off,sorry to be a pain in the bum but thats the only way it can be done...

You would need to start from the inside and work out to get a the TRUE angle and thread other wise you could double threaded it then the head is r00&ed.
Oh as to the helicoil idea scrap it......
Think of what the spark plug does and the need for a tight seal....
Then you will see why the only way to do it would be the way i was talking about.
 

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GU8 CRD
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Discussion Starter #3
Well I bit the bullet and picked up a "spark plug rethreader" for 20 bucks at a local engineering supply store and gave it a crack. Using a bit of grease to trap the filings and taking it very slow and easy, the plug now screws all the way in quite nicely. I think in my case some one just simply forgot to seat the plug properly at some stage in the past. There is a cavity between the thread and the seat of the plug machined into the head, so this makes an unseated plug look a lot more unseated then it actually was if crud gets past the seat into the cavity.
 

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nissan
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Close call mate if it was cross-threaded it would of been painfull....
To the wallet that is,glad it got sorted for a minimal cost...
 
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