Stripped spark plug thread

martinwiseman2000 · Unread post by **martinwiseman2000** » 23 Sep 2009, 08:56

Hi,

I recently had a stripped spark plug thread on my 2.0 16V Xantia as a result of a spark plug working loose and rattling in it's hole. By the time I noticed the knocking noise (which sounded exactly like a sticking tappet and could not be heard from inside the vehicle) it had probably done in excess of 1000 miles like this, the thread was completely gone, and the only thing holding the plug in was the coil pack.

I cured the problem by removing the head and taking it to a local engineering shop to have a helicoil fitted, however I have now read various websites which say that you can do the job with the head still on the vehicle by packing the helicoil tap with grease to catch the swarf.

For future reference how do people rate this idea? On a scale of 1 to 10 where 10 is "everyone does it this way, what on earth were you thinking when you took the head off" and 1 is "only a real cowboy would even consider trying it this way", where does it sit?

Thanks,
Martin.

jgra1 · Unread post by **jgra1** » 23 Sep 2009, 09:59

hi Martin, I have never fitted a helicoil, but despite that my approach would have been similar to yours..i.e remove items, get to the problem, get the problem off the engine, and get it sorted without contamination..
so for that reason I would have judged it a 1-3 ,

maybe 5 years ago I would have been a 8/9..

if that makes sense

saying that.. there are many jobs that when doing it properly gains very little and costs a lot of time...

I think a balance is needed..

my local bike shop repaired a plug thread on someones engine by keeping the bike on its side to prevent things getting in the cylinder.. ! he saved a small fortune and it seemed to work ok ..

John

Unread post by **Paul-R** » 23 Sep 2009, 11:19

My feeling is that on older cars, providing it was an aluminium cylinder head, then a few bits of aluminium would not cause a great deal of damage and would very quickly get blown out of the exhaust.

Nowadays with cats and FAPs I don't think it's a goer.

HDI · Unread post by **HDI** » 23 Sep 2009, 11:27

I've helicoiled plug threads in situ by using an industrial vacuum cleaner over the working area to remove the swarf. After the helicoil was inserted I looked inside the cylinder with a borescope and there were only a few minute pieces of alloy swarf in there , another application of the vac cleaner removed even them. Just make sure the valves are closed when vaccing.

handyman · Unread post by **handyman** » 23 Sep 2009, 23:41

Hullo, I have done quite a few of these on a whole variety of engines, without any mishaps. Sparkplug thread stripping is quite a common problem on alloy heads, but providing a few basic procedures are followed, the whole exercise is a cinch, and a darn sight quicker than having to remove the head, with all the extra hassle and cost involved. The last Xantia head I did, with it still on the engine, took no more than ten minutes. The owner was ecstatic as I saved them quite a lot of money.

I keep a whole range of helicoils, so if anybody nearby, East Sussex or West Kent, needs a repair, let me know.

Handyman

f00lzz · Unread post by **f00lzz** » 24 Sep 2009, 07:53

I had a spark plug 'ejection' which put a small dent on the underside of the bonnet! This was on a Triumph Dolomite (those were the days). Fotunately I worked at Dunlop at the time and their garage (for Company cars) quickly put a helicoil in whilst in situ. Incidentally this was the era of Denovo (run flat) tyres and all the Commisionaires (not security guards) were patrolling in Mini Coopers with run flats.

Unread post by **Paul-R** » 24 Sep 2009, 09:48

HDI wrote:I've helicoiled plug threads in situ by using an industrial vacuum cleaner over the working area to remove the swarf. After the helicoil was inserted I looked inside the cylinder with a borescope and there were only a few minute pieces of alloy swarf in there , another application of the vac cleaner removed even them. Just make sure the valves are closed when vaccing.

That sounds good. I change my opinion!