Spark Plug Nightmare - Crossed/Stripped Thread
Discussion
Nightmare......Tried changing my plugs today. Got to the third from the front on the drivers side and ran into trouble. Damn thing won't go back in properly and I'm sure I've stripped the thread a little. What can I do to get it sorted? Anyone have any experience of this? Could the first couple threads be ground out with everything still in situ?
Any advice gratefully received
Thanks
Ryan
Hi Ryan,
As an engineer I would say that it would be most difficult to carry out any thread correction with the head in situ.
The best solution, (if you really have stripped the thread out), is to Helicoil the plug thread and this will sort it properly.
You may be able to chase the original thread to reprofile it but this is normally only a temporary fix.
HTH
Roy
As an engineer I would say that it would be most difficult to carry out any thread correction with the head in situ.
The best solution, (if you really have stripped the thread out), is to Helicoil the plug thread and this will sort it properly.
You may be able to chase the original thread to reprofile it but this is normally only a temporary fix.
HTH
Roy
Offer it up again carefully by hand (you should *always* offer plugs up by hand and screw them down until they come up against the the sealing washer) and try to un-cross the threads. This won't take any more force than it took to cross then so should be quite easy to do, the only tricky part will be to get the plug lined up with the thread and get the first engagement. You won't have crossed more than the first one or two turns (unless you were a complete wally and kept forcing it when it was crossed) and this won't affect the overall strength enough to matter.
Hi,
I had a similar problem when I found a cross threaded spark plug on mine. The spark plug was done up tight but it was only half way screwed in. Spark plug thread chaser is what you need (as per blitzracing), its a thread tap with provision for a 3/8 ratchet. Just run it up and down the thread a bit at time with some WD40 taking it out every time to remove any swarf it collects.
Ozstyle
I had a similar problem when I found a cross threaded spark plug on mine. The spark plug was done up tight but it was only half way screwed in. Spark plug thread chaser is what you need (as per blitzracing), its a thread tap with provision for a 3/8 ratchet. Just run it up and down the thread a bit at time with some WD40 taking it out every time to remove any swarf it collects.
Ozstyle
Before anyone says this doesn't work - it does.
Get an old spark plug, cut the electrode off and tip out so you now have an "empty" spark plug.
Cut down the thread twice, 90 degrees apart so you end up with 4 cuts running down the thread.
Pinch end of plug on a vice so the 4 ends are touching each other.
Wire brush threads to remove edges.
You now have a tapered thread the same as a good one which will cut/straighten the threads in the head.
The trick is to get the angle right when going in, if you get the angle right and you haven't cross threaded it to death it works. WD40 the end, turn in/out slowly and when you are confident you have gone in far enough put another spare plug in with copaslip. Take out, put good plug in.
I watched an old boy do this when I was a kid and never forgot it. Thread chasers can do more harm than good if you get them slightly wrong. This method is slightly less drastic - but works if done correctly.
Get an old spark plug, cut the electrode off and tip out so you now have an "empty" spark plug.
Cut down the thread twice, 90 degrees apart so you end up with 4 cuts running down the thread.
Pinch end of plug on a vice so the 4 ends are touching each other.
Wire brush threads to remove edges.
You now have a tapered thread the same as a good one which will cut/straighten the threads in the head.
The trick is to get the angle right when going in, if you get the angle right and you haven't cross threaded it to death it works. WD40 the end, turn in/out slowly and when you are confident you have gone in far enough put another spare plug in with copaslip. Take out, put good plug in.
I watched an old boy do this when I was a kid and never forgot it. Thread chasers can do more harm than good if you get them slightly wrong. This method is slightly less drastic - but works if done correctly.
Ribol said:
Before anyone says this doesn't work - it does.
Get an old spark plug, cut the electrode off and tip out so you now have an "empty" spark plug.
Cut down the thread twice, 90 degrees apart so you end up with 4 cuts running down the thread.
Pinch end of plug on a vice so the 4 ends are touching each other.
Wire brush threads to remove edges.
You now have a tapered thread the same as a good one which will cut/straighten the threads in the head.
The trick is to get the angle right when going in, if you get the angle right and you haven't cross threaded it to death it works. WD40 the end, turn in/out slowly and when you are confident you have gone in far enough put another spare plug in with copaslip. Take out, put good plug in.
I watched an old boy do this when I was a kid and never forgot it. Thread chasers can do more harm than good if you get them slightly wrong. This method is slightly less drastic - but works if done correctly.
Thi is a good trick from the good old days,done this a coulpe of times myself to get some one otu of trouble,same bloke different times,different car,some people never learn!.Get an old spark plug, cut the electrode off and tip out so you now have an "empty" spark plug.
Cut down the thread twice, 90 degrees apart so you end up with 4 cuts running down the thread.
Pinch end of plug on a vice so the 4 ends are touching each other.
Wire brush threads to remove edges.
You now have a tapered thread the same as a good one which will cut/straighten the threads in the head.
The trick is to get the angle right when going in, if you get the angle right and you haven't cross threaded it to death it works. WD40 the end, turn in/out slowly and when you are confident you have gone in far enough put another spare plug in with copaslip. Take out, put good plug in.
I watched an old boy do this when I was a kid and never forgot it. Thread chasers can do more harm than good if you get them slightly wrong. This method is slightly less drastic - but works if done correctly.
And I totally agree it worked well both times
I did this on my Saab - first thread knackered. - i considered using a thread tap but didn't want to cut a new thread and have loads of swarf in the engine. Afer looking round i found this:
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200355940_200355940
a 'back tap' which is used to pick up the original inner threads, then you tap from the inside out. Which seem a good idea. There are a few companies that do them - all in the USA it would seem however. I've yet to try it though...
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200355940_200355940
a 'back tap' which is used to pick up the original inner threads, then you tap from the inside out. Which seem a good idea. There are a few companies that do them - all in the USA it would seem however. I've yet to try it though...
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