Stuck Spark Plug

fknjexx · Postby **fknjexx** » Sat Aug 08, 2015 8:25 pm

Hey guys,

I've got a stuck spark plug (1st one) and I'm guessing it's been a problem that hasn't been resolved ever since the early owners of this car (maybe they screwed it in too tight). I recently brought my car to a local mechanic get the problem solved & he still couldn't manage to get it out lol. So if anyone had this problem before or could recommend a mechanic in Sydney, NSW that can crank it out or so please leave details below!

Cheers.

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manga_blue · Postby **manga_blue** » Sat Aug 08, 2015 9:44 pm

I've had this a couple of times but not on an MX5.

If the car is using LPG or running lean then you can get a ring of rust around the bottom of the spark plug's thread. If you try to screw it straight out then the rust will carve out or crush the thread in the head. With a bit of luck you can work at getting the plug out by loosening it half a turn or so, pouring Penetrene down the side, tightening it and trying again, bit by bit until you crack the rust off and it screws out relatively free. If the damage is not too bad you can restore the thread well enough by screwing in and out a few old spark plugs.

If you can't remove it because someone before you stripped the thread then it's a bit harder. I fixed my Astina by taking the car to a machine shop. They had a socket which locked onto the plug so they could unscrew and pull on the plug at the same time. The only real option then is to drill out the plughole and put in a helicoil. It's better to let an experienced helicoil user do this. Helicoils aren't ideal but they're a lot better than a plug which flies out under load and puts a dent in the bonnet.

Magpie · Postby **Magpie** » Sun Aug 09, 2015 10:29 am

Have you tried warming the engine up then trying?

A little WD40 type stuff down the hole and leave overnight? Don't do this if engine is hot...

A proper spark plug socket and a light rattle gun?

When you get it out put a LITTLE never seize on it.

gslender · Postby **gslender** » Sun Aug 09, 2015 2:37 pm

Also, sometimes striking it while half strength turning can loosen seized bolts. The impact strike pushes the threads apart and a firm turn at the same time can just be enough to loosen. Good luck

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Postby **NitroDann** » Sun Aug 09, 2015 3:16 pm

The way a socket grabs a spark plug that wont do anything.

Mr Morlock · Postby **Mr Morlock** » Sun Aug 09, 2015 6:58 pm

manga will hate me suggesting it but talk to a mechanic in your area and ask them if they have experience in removing stuck spark plugs. Mechanics have the gear and they have the expertise. Don't even think about trying drill it out and bear in mind that its really easy to break a plug on the insulation then you cannot drive the car. Rattle guns are also not all the same i.e. the diy home mechanic generally does not have high torque guns. A head guy might actually be a good start- they must see this regularly .

manga_blue · Postby **manga_blue** » Mon Aug 10, 2015 12:30 am

Normally mechanics pass these jobs onto machine shops (also called engine reconditioning shops). They're the ones with the tools for it.

greenMachine · Postby **greenMachine** » Mon Aug 10, 2015 9:24 am

Am I the only one who remembers the earlier thread on this subject? How did that one end?

:mrgreen:

fknjexx · Postby **fknjexx** » Mon Aug 10, 2015 1:07 pm

Cheers guys I'll start asking around and see if there's any proper mechanic/machine shops that could help, As NitroDann said the socket pretty much doesn't do anything at this rate, it just won't bloody turn. Plus I'm not really keen on doing it myself / drilling a hole in it.

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gslender · Postby **gslender** » Mon Aug 10, 2015 1:20 pm

fknjexx wrote:As NitroDann said the socket pretty much doesn't do anything at this rate, it just won't bloody turn.

If the socket sits on the spark-plug itself (mine do) then you can strike the top of the socket extension bar, and with a 2nd set of hands, gently turn the extension bar with a spanner or similar. The act of striking a seized bolt will loosen/break free the threads - but agree that doing this to a spark plug is difficult as you need to be applying downward pressure for the strike but without destroying the plug in the process. I'd also be careful with an alloy head so start off with gentle strikes and don't go all The Hulk with a sledgehammer!!

You never need a lot of pressure and I've removed several jammed bolts in the past with only gentle turning pressure and 1 single well timed strike that does the trick.

Also, doing it once in reverse (tightening) and then again the other way, can also be enough to break the thread the let the bolt undo.... it is surprising how well this trick works on many threads (including Philips and Flat-blade metal screws that are visually rusted solid).

Good luck.

G