Snapped spark plug - what next?

[merkyworld]

Hi all, I was doing an oil, filter and spark plug change this evening. All going well until I snapped the last plug off, leaving just the thread in.

The car is a 1988 W124 E230 Estate.

Should I:

Try and drill it out / helicoil
Try and find a secondhand head
Other?

 

[Rob77]

If you feel you have to ask then I think I'd put it into a garage to fix (personally I would anyway). I certainly wouldn't go trying to drill it out and risk bits of old plug dropping down into the engine.

 

[Value Motering]

Take a little bit of time.

I would be tempted to section/cut/break the other plugs you removed to the same as what is still fitted in your car.

It may give you a good idea of watts possible.

But don't make a bad situation worse.

Are there any health issues cutting/drilling these plugs fitted, may be check, thought I heard some plugs have some strange materials in use, beware.

I would also pop down to a few local good garages and seek their advice.

I would guess if it's tricky, a good local Engineer/garage will get best results.

Good luck....

 

[Dash1]

Hi all, I was doing an oil, filter and spark plug change this evening. All going well until I snapped the last plug off, leaving just the thread in.

The car is a 1988 W124 E230 Estate.

Should I:

Try and drill it out / helicoil
Try and find a secondhand head
Other?

Hi merkyworld,

Sorry to hear of your dilemma.

Firstly, when you say that the spark plug has "snapped off", are you actually saying that the remainder of the plug came away with the electrode and the heat insulator tip intact, thereby only leaving the threaded section within the cylinder head.

If you are, then you may be very lucky and get away with just using an appropriate "easy-out" . If not, then you really do have a problem.

Do not under any circumstances attempt to drill it out whilst in situ, the results will only prove to be catastrophic. If any of that metal swarf or indeed the metal filings does in fact get lodged between the piston and the cylinder wall, and it surely will, then you will destroy the cylinder liner, thereby creating loss of compression and piston blow-by.

Your only and the correct solution is to remove the cylinder head and do the job properly, and at considerable cost to you if you are not able to do this work yourself.

The cost of the parts alone, head gasket set, stretch bolts, head skim, etc. would prove to be quite expensive. If you are not able to do it yourself, then any competent mechanic/garage would do this for you but I would think that it will run into many hundreds of pound to rectify.

With the greatest respect, you say that the vehicle is in fact a 1988 model, I would also consider whether such a repair would be deemed cost effective given the age of the vehicle.

A helicoil is normally only used for the purpose of stripped threads, even then, the head should be removed even to do this job properly. A secondhand head may very well be an alternative solution, but even then you would still have to skim the cylinder head and possibly overall it - decoke, new valve seals etc. This alternative would prove to be even more expensive because you would have to source such a cylinder head and the overall costs in doing so.

Regards,

Dash1

 

[Dieselman]

The right Ezi-out should get it out combined with some penetrating oil and heat.

 

[bigfatjim]

I think the key issue here is whether the 'nut' of the plug is still there. if so, no reason why it cannot just be undone as usual. If on the otherhand it snapped below the nut, this would be a first for me in 30 years of fixing cars. I really cannot see how that could happen unless you turned it the wrong way or it had pehaps been welded into the head!

If it is snapped between the nut and the head then I would sugget the only real option is head removal to be 100% safe, but no real reason why you cannot drill if you are sure the piston is out of reach and that you do not drill any part of the head itself including threads. No reason why you cannot vacuum out any debris with a good dyson with a bit of rubber hose just smaller than the plug hole once removed. There is a small risk of debris between the piston and liner, but it all depend son how much you like gambling.

Hope that helps.

 

[Value Motering]

Poss bodge job, but may work.

Is it possible to weld/fix the HT lead/cap on the bit (conductor) of the broken plug, might be like Dentist work, root canal/post and cap.

But don't get a Dentist to do it, prob cheaper at a MB dealer....

 

[Dieselman]

All he has left is the metal thread, no ceramic, no conductor.

Ezi-out or weld a nice fat bolt into the steel bit and unwind it after lots of penetrating oil.

 

[1speed]

Same thing happened to me with an old Vauxhall Carlton. Only solution was to remove the cylinder head, drill and ezi out the old spark plug, re-skim the head and refit.

 

[Ian B Walker]

Am I right in thinking that this is an M102 engine? If so the plugs are fitted at an angle on the side of the head. This would make accurately drilling out in situ nigh on impossible. You would probable end up lifting the engine, if not taking it out altogether. Why not just bite the bullet and lift the head. Much easier and less risk. Quicker too plus the fact that you would at least know that the head gasket is new.