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[omegod]

Well the bargain 728i bought appears to have a hidden horrors! It was misfiring so I suspected a dodgy " pencil" coil pack, on removing them number 5 is melted/burnt/destroyed and lo and behold the plug beneath is in a helicoil that appears to have worked it's way out with the helicoil, amateur effort by the looks of it.

Anyhow it's life now hangs in the balance, I can break it and make some cash as I paid buttons for it but it's that nice I would rather see if it can be revived. The thread appears non existant in the plug well which is odd as helicoils need a thread to wind into.

So! can it be recut and an oversized helicoil/time sert be fitted?  and could this be done in situ?

Any suggestions of a decent place/person in the North west?

[o-meg-a]

could re-do the helicoil i imagine. if there is no thread there then that suggests an amateur job as you say, like someone has knocked the helicoil in somehow.
It would come almost straight out of course. but who knows.

Either way, i dont see why you wouldnt be able to do it again.

[o-meg-a]

as for doing in-situ,

Might be more difficult as the little "tang" ont he end of the new heli coil would need to be tapped through....you might be able to pull it out instead of tapping it through, but that would be awkward.

Other than that, you're going to have metal swarf/shavings from the new thread being cut.
So.......
unless you have a way of stopping that going into the engine..
You'd have to do it off the car.

Would be nice to save it.But unless you can do it on the cheap, it may be better to break or try to sell on whole.

[omegod]

I remember reading about someone filling the cylinder with squirty cream, doing the helicoil then spinning the engine over to spit it all out of the plug hole it worked but I don't fancy it myself!

[activamad]

If you do this, make sure the valves are closed on that cylinder as had to remove the head on a Carlton once when someone had decided to retap the plug hole and tapped a thread into the valve. Needless to say it didn't run well.

[Chris_H]

Unless you can turn the engine upside down to tap the plug hole, the swarf will fall into the bore and cause you another problem a bit later.

The head needs to come off at the very least.  Can't you get a s/h head?  I know it's a pain but having a plug come out when you're driving can be disconcerting to say the least.   Of course you may be proposing that that calamity happens to someone else?

[Lazydocker]

Sorry to hear this... It's a good bet the seller knew as well, considering the price

[Kevin Wood]

Given that one attempt to helicoil has failed, would it not be a better bet to bite the bullet and have a look for a decent head?

[albitz]

Its going to be a "head off" job whichever route you take to try to fix it. I would agree that another head is the way forward.
Dont know how much a good head would be from a breaker, but to do all that work and still have the possibility of the same thing happening again to the old head.....
I think it would be worth doing the job properly, as imo its a gorgeous car.

[omegod]

Been thinking about this and have had an engineer say he is confident he can do it for £40, albeit with the swarf risk on my head be it, apparently it's an ally head so magnets wont clear it. Apparently pulling the head off opens up a gammut of other issues as the head bolts usually strip their own threads when torquing them up i.e more bloody helicoils or new complete engine.  The existing helicoil doesnt appear to have been drilled or tapped in and more like some numpty has threaded a helicoil onto the plug and tried to stuff it in the head.  I will update as I go forth with this one!

[r1]

just areldite it in then flog it quick.

[albitz]

just areldite it in then flog it quick.

Mental note - never buy anything from R1.

[omegod]

just areldite it in then flog it quick.

My conscience wouldn't let me do that R1, it only owes me £450 and I think the wheels are worth that alone.

[sierrapaul]

you could prob pick up a good second hand engine for around 200,300 quid as its a 2.8 same engine as any 3,5 or 7.think thats the way id go cos its a lovely car and one of the best bmw`s made.they drive so nice nothing else like em

[o-meg-a]

This is a viable option i would say if you could swap it yourself.

But if you have to pay a garage to do the engine swap it becomes uneconomical.

As for the Helicoil, I say have a go at it.
Worst that happens is you break....or sell on as a project for the money you bought it for.

no loss