ChrisW
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| posted on 4/3/08 at 01:36 PM |
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Stripped head
Mate asked me to look at his car which had a suspected exhaust manifold/gasket failure. Spent a good hour fiddling with it, and couldn't spot
any leaks, so was starting to suspect head gasket and started taking the plugs out to do a compression test when we discovered...
Turns out the plugs were far too loose, probably had not been done up properly at the last service (by Peugeot main dealer). Two needed no effort on
a small ratchet to undo them, one undid with my fingers.
Dealer of course is denying all knowledge, as they would.
Plug on cylinder 2 has come loose, destroyed the coil pack, and knackered the thread in the head.
So, what do I do...??
Can I helicoil the head? Will it take the compression?
If I take the head off, can it be re-tapped or will it need a new head?
Or, bodge solution... can I just retap it in situ, hope not too much swarf goes down the bore, stick a new plug in it (maybe a bigger one) and advise
him to part ex it at said main dealer ASAP?? 
FYI, car is a 306 1.8 16v on a V plate. Very tidy car, one owner, full Pug service history. It's a keeper rather than a scrapper.
Chris
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r1_pete
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| posted on 4/3/08 at 01:41 PM |
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Plug threads can be recovered using helicoils, but it changes the way heat is dissipated and may need a different grade plug in that pot. I have heard
of them being done in situ, with grease on the tap to catch the swarf. But you need also to make sure the tang which breaks off the coil during
fitting is recovered. Dodgy but I'd go for it, getting running ok, and chop it in.
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britishtrident
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| posted on 4/3/08 at 01:46 PM |
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Agriemach can supply the rethreading kit
http://www.agriemach.com/advanced_search_result.php?keywords=plug&x=0&y=0
These guys are a good supplier of coil packs
http://www.ignitionleads.co.uk/Mod.aspx?Man=PEUGEOT
[Edited on 4/3/08 by britishtrident]
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ChrisW
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| posted on 4/3/08 at 02:50 PM |
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quote:
Originally posted by r1_pete
But you need also to make sure the tang which breaks off the coil during fitting is recovered.
Thanks Pete!
What do you mean by the above??
Chris
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r1_pete
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| posted on 4/3/08 at 03:47 PM |
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On a helicoil, there is a tang at the bottom, which is used by the insert tool to wind it up so it is a smaller diameter and screws in easier
(remember it is a coil), when in place the coil is released and it expands to grip. This tang is then broken off to allow a through thread.
Looks like the inserts BT refers to above are better for a diy operation, they are solid rather than a coil, for £11 looks like a good option, but,
threadlock them in, I bet on a sooty old plug they can screw out with the plug.
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dhutch
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| posted on 4/3/08 at 04:35 PM |
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A helicoil coil:
http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Helicoil_14x1.25.jpg/530px-Helicoil_14x1.25.jpg
Note the nick in the nearest point of the first (top) coil. This onwards is the tang, which is broken off, and idealy not left in the enigine!
hutch
[Edited on 4/3/08 by dhutch]
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Mr Whippy
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| posted on 4/3/08 at 04:56 PM |
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If your worried about the heat path for removing the heat from the plug changing, then use some copper slip on the plug thread and this will restore
it. Anyways good practice to do anyway.
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blue2cv
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| posted on 4/3/08 at 07:46 PM |
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I use Wurth inserts, they are a solid insert that spreads to lock itself in as it bottoms out on its shoulder. no bits to snap off and can be fitted
in situ
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ChrisW
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| posted on 5/3/08 at 01:44 PM |
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Thanks guys. He's persuing the legal angle at the moment, so hopefully I won't get the job of fixing it... something tells me he
won't get anywhere, but it makes him feel better.
May well be back for more advice if/when I actually have to go the job!
Chris
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