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Post by stiff on Mar 17, 2017 18:32:07 GMT
On the drive home this evening my no. 3 spark plug went Elon musk on me and tried to get to Mars. It's left a tear inducing dent in my pristine bonnet and now won't go back where it belongs. Can anyone help?
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Post by Horney on Mar 17, 2017 18:40:16 GMT
It might well have stripped the threads in the head. Probably a head removal to investigate I'm afraid.
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Post by atlex on Mar 17, 2017 19:04:22 GMT
try another spark plug from another cylinder that didn't go pop. if it won't go in either, those threads are stripped
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Post by thruxton on Mar 17, 2017 19:14:17 GMT
I use to work a lot on Triumph Stags. Yes, I know.
Anyway they often did it. If you have stripped out the thread. You can Heli Coil insert in situ if you take care.
Regards. Rich.
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Post by stiff on Mar 17, 2017 19:18:10 GMT
try another spark plug from another cylinder that didn't go pop. if it won't go in either, those threads are stripped Good suggestion. I'll give that go tomorrow. My local mazda specialist seems to think that he can re tap the thread. Is that an option?
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Post by thruxton on Mar 17, 2017 19:34:58 GMT
That's a Heli Coil insert.
If the thread has stripped out then you can't re-tap it because it's taken the metal away and left a bigger hole which the sparking plug just flops around in. You have to INCREASE that hole size, thread that for the Heli Coil insert and after that is screwed in that then leaves you with a thread on its inside face that is the correct size for your new sparking plug.
Rich.
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Post by Rickster on Mar 17, 2017 20:52:11 GMT
So what would cause that to happen?
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Post by thruxton on Mar 17, 2017 21:38:24 GMT
Very often the last person to put the sparking plug back in crossed the threads on it. This then because they are aluminium threads tears them and the SP over time loosens up and the compression eventually blows the SP out taking the rest of the thread with it.
In old cast iron heads often the opposite would happen. Cross threads lead to seized plugs and then getting them out tore the thread out of the head at the same time. Again a job for a Heli Coil insert.
Over the years I've replaced many but always managed to do it in situ. Plenty of heavy grease on your tools, oooer, to hold onto the swarf.
Regards. Rich.
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Post by stiff on Mar 19, 2017 15:26:36 GMT
Tried another plug and it didn't work. I'm a bit concerned now!
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Post by atlex on Mar 19, 2017 18:26:57 GMT
retap & helicoil or a new head. sorry stiff get used to the idea :-)
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Post by stiff on Mar 20, 2017 13:38:44 GMT
retap & helicoil or a new head. sorry stiff get used to the idea :-) Dropped it off at a local Mazda Specialist (he did my cambelt and fluid changes too) and he's tapped and helicoiled the head and I now have four working brand new plugs. At the same time he's fitted a 2nd hand cat as mine bust badly while trying to make alterations. So, head tapped, new plugs and a replacement cat for £80. Not too bad I thought. Just need a new bonnet to replace mine now.
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Post by minty on Mar 20, 2017 21:37:42 GMT
That's an absolute bargain!
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agt
New Here
Posts: 11
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Post by agt on Mar 21, 2017 12:56:00 GMT
retap & helicoil or a new head. sorry stiff get used to the idea :-) Dropped it off at a local Mazda Specialist (he did my cambelt and fluid changes too) and he's tapped and helicoiled the head and I now have four working brand new plugs. At the same time he's fitted a 2nd hand cat as mine bust badly while trying to make alterations. So, head tapped, new plugs and a replacement cat for £80. Not too bad I thought. Just need a new bonnet to replace mine now. That's great news!
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