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MG MGF Technical - Blown spark plug

Sadly my '96 VVC blew a spark plug the other day resulting in the thread being stripped and a nice bill to remove and put a heli-coil into the cylinder head.

Has anyone heard of this happening before ?? The car was always lovingly looked after (by the previous owner...my Mother!!) and always serviced by Rover (personally I wouldnt be too bothered).

Any advice is good and I might also add that even though it has low mileage - 47k - for a car that age......it has never had a HGF !! So not all bad.

Does anyone think I might get some comeback via the Rover/MG garage that has always serviced it??
A Smith

Lightly that either the plug wasn't put in tight enough, or the plug was put in too tight, it has come up here before a couple of times, preceeding noise 'sounded like a diesil'?
Will Munns

Will, I thought all VVC's had the aural qualities of an 'oil burner' mine certainly does.
Phil

It did sound a little rough and lumpy prior to it happening (just a week after I took ownership of it) but upon checking it out I was told "I dont know, it has always sounded like that".

From what you say, I must have something to stand on back with the servicing garage if they had not put it in properly !! I am going see what they say but to be fair its not the most expensive car repair I have seen before (€600) - previous car was a VERY unreliable Rover.

Cant wait to get it back too as I guess this meant it wasnt running as well or as quick as it is was supposed to, which = more fun than I was already having !!!
A Smith

I know of one previous instance of this, and it was the owner's fault, Graeme B had changed the plugs himself and not tightened them up properly. When the plug blew it left a big dent in the engine bay cover. (See archive.)

But if you think your plugs have been changed and not tightened you'll have to have some proof.

Rover reccommend changing the plugs at 60k miles. If your mother had the car serviced religously she would have had the 60k service done in 2001 - its 60k or 5 years.

Find the (expensive) bill and see if they charged you for new plugs. If your mum has lost the receipt go and ask the dealer for a copy - they should have one on their system.

Now the fun starts convincing them that no-one else has touched the plugs since then - so it must be their fault.

It might help if the repair work is being done by the same dealer.

Good luck

jt
John Thomas

Self ejecting plugs has happened to a couple of fellow BBS'ers - Graeme's was certainly the most, er, 'celebrated'

Over-tightening is the commonest cause, I am told, as the head is alloy and therefore much more sensitive to spark plug torque than your common or garden iron heads...

Unfortunately not much use to you - but as JT says, worth following up with your garage, as they are the only ones who'll have touched the engine.
Rob Bell

Thanks for all the advice, I might just have to inform of the outcome in a week or three !!
A Smith

Have seen this before when a customer left this 'simple' job to her local garage rather than bother me to change the plugs 8-0. I managed to helicoil it without removing the head after machining some special tools for the job, still took a few hours though but a lot cheaper than a head off job. We did that later when her husband blew the HG!
Mike.
mike

>>Over-tightening is the commonest cause<<
Really ? I guess that does make sense. I've always wondered why the plugs don't come out on my bike - they're only done up to 11NM (against 25NM on the F). Mind, looking at where the rear cylinder of my V-twin points, It could be *very* painful if that plug gets fired out !
Steve


I did it.

Had a stripped thread on way to a certain notorious stag do!!

Car was indeed "rough" for a few miles... and I thought nothing of it.

Take the opertunity to get some head work done. It is the cheapest chance you will have.

Also, be very careful of helicoils.
I had mine helicoiled and the helicoil came out(!!) when the plugs were next changed. May be better to use an insert instead.

NB. Both helicoil and insert can be done WITHOUT removing the head. It will be MUCH cheaper... but has its risks.

Drop me a line if you want more info on any of the above.

Paul.
(EmailMe at nothard dot org dot uk)
Paul Nothard

This thread was discussed between 18/11/2003 and 19/11/2003

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