Hi,

One of the spark plugs on my car has jumped out when I started the car. I've tried to refit a (new) plug and it doesn't seem as if there is much grip on the thread. It feels like the thread has stripped but I'm not sure if the plug goes in very far before it "jumps".

Does anyone have any ideas on this? I'm guessing it's new head time but I'd love to be wrong.

it does soundlike somebody has overtightened the plugs, and the compression has been enough to force to strip the thread. As you say its most likely new head time.

Not necessarily a new head. The same happened to our Octy (1.6 litre AKL engine). The garage managed to put a new thread coil in the head. It was expensive enough, thank you, but not as bad as a new head.

A thread coil properly mounted is as strong (or stronger) as the original thread.

Here's one type of coils that can do the trick (there are others out there):

Heli-Coil ( HeliCoil Inserts ) Helicoils Screw Thread Inserts | Emhart.com

Not a DIY job, though, since you need special tools (unless you could borrow a kit, of course).

dont bother with a helicoil for a spark plug thread, they dont last very long and often they are a nuisance to keep gas tight... try a time-sert insert from wurth..

Many thanks. There might be hope after all. I doubt the Time-Serts are a DIY job?

Now to find someone who can do the job (but I now know what job I want doing). They'll need to collect since the car is stuck at home with only three plugs in :-(.

Thanks again.

you'll be able to drive it without a spark plug in so long as it's not for a long distance..

dont bother with a helicoil for a spark plug thread, they dont last very long and often they are a nuisance to keep gas tight... try a time-sert insert from wurth..

Agree......had this done recently on a motorbike and all seems to be well.

Mate had it done on a 540 BMW and they done it in situ.......no problems in 2 & a half years!!

I've found someone to do it now. It seems that it will cost ~£60 to do it "in situ" (ie without removing the head) but they say there is a risk of swarf getting into places it would better if it didn't go.

you'll be able to drive it without a spark plug in so long as it's not for a long distance..

I'm still not sure about this, won't the unburnt petrol be (partly at least) exhausted out the open spark plug hole and all over the engine?

Hmm, If the size of the swarf is small then it might be good to get it done, run if for a small distance say 100 miles to get it into the oil flow and then change the oil and a filter including a flush.

Other thing is to put a small piece of pipe on the end of the hoover and pop it down into the spark plug hole before fitting the spark plug to take out any bits you can.

I think they will vacuum the cylinder but good tip about the oil change.

Thanks.

I've found someone to do it now. It seems that it will cost ~£60 to do it "in situ" (ie without removing the head) but they say there is a risk of swarf getting into places it would better if it didn't go. I'm still not sure about this, won't the unburnt petrol be (partly at least) exhausted out the open spark plug hole and all over the engine?

Quite likely. I'd probably get it towed by your recovery company I think.

. I'm still not sure about this, won't the unburnt petrol be (partly at least) exhausted out the open spark plug hole and all over the engine?

unplug the fuel injector for that cylinder:)

unplug the fuel injector for that cylinder

o|, I hadn't thought of that. That is to say I hadn't thought they'd be that easy to unplug.

Thanks I'll have a look at that.