Opti Plug X-thread fix

[PeterM]

So , having established the plug thread in No1 cyliner is screwed (no pun intended) , options seems to be ;
1) Get a new plug in somehow
2) Take off the head & put an insert in
3) Buy a new head.

Clearly No1 is not ideal , but could work if the correct thread can be picked up somehow ( maybe runa tap/di down ( not sure which is which but you know what I mean) without taking the headoff & 'try & get any bits out' & hope anything left gets burn't up / chuched out of the exhaust .

No2 seems to be the best/ cheapest proper fix

No3 will I guess cause a big cost which I'd rather avoid.

Anyone have any experience of this & then fixing it/ costs ? I'll be paying someone else to do it whatever as I dont the time / ability to do the second option & the first is very 'iffy' and I'm trying not to think about the cost of a new head !

[JABS]

Take the engine to someone who can fit a Heli Coil. They tap the hole and insert a coil which provides the correct size thread. No need to remove the head. Takes a few minutes.

You can easily do it yourself if you are handy.

Good luck.

[PeterM]

Cheers JABS - its with the local Merc dealer, but I would have thought that runing the TAP down would drop metal chips into the cylinder, & when turning it over they could score the bore to buggery.

I'll give them a bell to get thier view & hopefully they can do it with it without taking the head off. Keen to do a real fix like this than a bodge , ending up with a loud bang & nice plug shaped hole the cowling when I doing 5,000 rpm !

[JABS]

They will use a special tap and liberally cover it with grease. There is little metal removed and most of it comes out on the tap.

They then screw in the helicoil with a special tool and off you go!

It is a standard repair used all over the place where threads become galled or stripped.

You probably put as much swarf into the cylinder when you crossed the thread in the first place.

Hope it goes well.

[bedajim]

Originally Posted by JABS

Take the engine to someone who can fit a Heli Coil. They tap the hole and insert a coil which provides the correct size thread. No need to remove the head. Takes a few minutes.

You can easily do it yourself if you are handy.

Good luck.

Not used them for years but don't you have to re drill & tap the hole bigger to fit the Heli coil ?

You can get a thread cleaning tool (looks like a very blunt bottom tap) for spark plug threads we used to use them before doing pressure tests, you may be able to try something with one of those, if not I think it's head off and retap for the Heli Coil

[bedajim]

Originally Posted by JABS

They will use a special tap and liberally cover it with grease. There is little metal removed and most of it comes out on the tap.

They then screw in the helicoil with a special tool and off you go!

It is a standard repair used all over the place where threads become galled or stripped.

You probably put as much swarf into the cylinder when you crossed the thread in the first place.

Hope it goes well.

Google is my friend

http://www.engineproblem.com.au/helicoil.htm

[PeterM]

I'll see what they say about if they think they can do it with the head off or not. They will be the ones that will take the wrap if the plug comes out at high speed ! I can only assume it cant be a too big a deal to take the head off . I've done it on cars myself ( years ago ) & thats with all the valves etc sat on top . I'd guess it 'should' just be a case of disconnect everything , undo the bolts - tap the thread , insert insert - new gasket - tighten the bolts up & re-connect the bits & pieces !

Always a trade off between cost / hassle on these things, but if you have all the right tools I've always found it alot easier !

[Nos4r2]

It's a good excuse to pop the head off and have a look at the state of your water galleries. After all, it's not got a tonne of valvegear in the way.I'd still helicoil it with it off-or if it's bad then use a timesert (google it) though I'd grease it liberally to stop salt water getting on it if you use a timesert.

[Dirk Diggler]

Tell whoever does the job to be careful, cos a new head is £1,100+, and they'll need to replace the o rings!

[PeterM]

Holy crap - £1,100 quid !- I think I'll be telling them to take it off & do it very carefuly !

Thanks Nos I'll get on to Google now !

[PeterM]

Looks like you can get away with just tapping the hole ( if you dont need to get a stud out by drilling, & even then if you do it carefully you may get away without drilling it out) for a helicoil, but looking at the timesert details I cant work out what the advantage of one over the other is.

Helicoils seem to have worked for years, and the timesert seems to be a slighlty differant way of doing the same thing ( unless I am missing something )

[Nos4r2]

Originally Posted by Blackroady

Looks like you can get away with just tapping the hole ( if you dont need to get a stud out by drilling, & even then if you do it carefully you may get away without drilling it out) for a helicoil, but looking at the timesert details I cant work out what the advantage of one over the other is.

Helicoils seem to have worked for years, and the timesert seems to be a slighlty differant way of doing the same thing ( unless I am missing something )

If it's too badly damaged to get a helicoil in there (for example a drill slipped while drilling out, or the helicoil won't stay in)then the timesert allows you to take it out further.

[martini]

Originally Posted by Nos4r2

If it's too badly damaged to get a helicoil in there (for example a drill slipped while drilling out, or the helicoil won't stay in)then the timesert allows you to take it out further.

I use Timeserts over helicoils every time. Much easier to fit and much stronger. Techs at the local Mercedes dealership keep breaking the glow plugs off and its a 2 day job to remove and refit the head. So they send it to me and I drill and fit a timesert. I don't use grease to hold the swarf as you cant get it back out the hole (its an M8 fine), just keep it dry and blow it out with an airline. I make sure theyre aware of the risk and pass on responsibility to them, so far none have come back smoking and rattling

[Nos4r2]

Originally Posted by martini

I use Timeserts over helicoils every time. Much easier to fit and much stronger. Techs at the local Mercedes dealership keep breaking the glow plugs off and its a 2 day job to remove and refit the head. So they send it to me and I drill and fit a timesert. I don't use grease to hold the swarf as you cant get it back out the hole (its an M8 fine), just keep it dry and blow it out with an airline. I make sure theyre aware of the risk and pass on responsibility to them, so far none have come back smoking and rattling

On the opposite tack, I've has a timesert come out on a couple of occasions because it's rusted to the exhaust studs on a bike and salt from the roads has ingressed and has destroyed the timesert outer thread(hence saying grease the outside to prevent water ingress). I'd always use a helicoil first-it means there's still the option of a timesert,whereas the timesert is the last option.

[codprawn]

You could use a thread chaser tool to see if you can clean up the thread - basically it is a large tap to recut the exsisting thread.

http://www.frost.co.uk/item_Detail.a...on&subCatID=27

Much easier if the thread isn't too badly damaged.

[Nos4r2]

Originally Posted by codprawn

You could use a thread chaser tool to see if you can clean up the thread - basically it is a large tap to recut the exsisting thread.

http://www.frost.co.uk/item_Detail.a...on&subCatID=27

Much easier if the thread isn't too badly damaged.

You can make one with an old spark plug if you're handy. I made one a while back that's got no central electrode but a bit of hose sticking out so I can attach it to a 12v vacuum cleaner(via a shedload of gaff tape)to suck up any swarf.

[AVONMON]

Hi,if the head off is the preferred route it would be worth helicoiling the rest of the plug holes,they used to run out at @ £6 each.Cheers

[PeterM]

Thanks for all the advice . Have just been up to the boat & its all done , fixed , serviced , winterised , lifted , covered ,the lot now.

In the end it was deemed a head off & helicoil job. All the other plug threads were OK & the plugs could be screwed in by hand ( until the end ) . Am pleased they fitted the coil , as , as was said it means if it fails I can then go down the timesert route.

Now I'm just waiting for the bill ! So £110 for plugs , etc etc - I just wont tell the wife - and thats before the lift / wash / store !

Still on a plus side I have fitted my ebay cover properly for the first time & people thought its was a full on tailored cover ! A bit long at the back , but needed the length to get the width to cover the cabin. A few quick cuts with the knife & hey presto - now runs just over theback of the motor , which should stop the rain collecting on top & allow a bit of airflow ! Roll on Spring !

[Bigmuz7]

Good stuff .. Just for the record chaps didnt see this thread till now,.. I've used helicoils to good effect. On an alloy head I assumed any swarf that I couldnt recover would just get burned or blown out as it is fine stuff, and light, and would'nt really cause that much damage for all the tiny amount that would have been left, any one found this to be different ?

[ian parkes]

£110 for plugs , spark plugs surely not .

I know dealers take the P**s but