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[Paul M]

I was driving to my folks' on Saturday when the car started making a rather unpleasant noise. I was just going through the centre of Glasgow on the M8 so pulled off at the next junction to have a look. Switched off, popped the bonnet to have a look but nothing obvious. Started it up again to the sound of an awful popping noise on every revolution. Still couldn't work out the cause so I called for recovery (first time I'd ever had to do so since I started driving at 17).

The guy arrived some time later, and after some prodding around discovered that one of the spark plugs had come out (middle plug on the passenger side).In doing this it had also wrecked the lead, so no chance of a quick repair by replacing the plug. So the car was trailered to my folks' place and I used my BMW to get back home -- glad I've got two cars then.

So as it stands, hopefully I can just replace the plugs and leads, and it'll be OK. It's possible the thread has been damaged, in which case it'll need rethreaded first, but that's not really a big deal. My main fear is that part of the plug has broken and got into the cylinder, although the mechanic who recovered me said it's likely that the combustion chamber pressure would have blown it outwards. Just need to wait and see.

I'm quite surprised at this happening, the plugs were last changed about 20,000 miles ago so it's unlikely to have been caused by incorrect tightening. Has anyone else ever experienced such a thing? If so do I have anything to fear regarding damage to the engine?

I was planning on replacing the rocker gaskets and fitting new plugs and leads anyway so this will just hasten my need to do so -- probably next weekend if I can get the parts and the weather is good. Here's hoping it runs OK afterwards as I really don't fancy the prospect of having to remove the head.

[Markie]

I was driving to my folks' on Saturday when the car started making a rather unpleasant noise. I was just going through the centre of Glasgow on the M8 so pulled off at the next junction to have a look. Switched off, popped the bonnet to have a look but nothing obvious. Started it up again to the sound of an awful popping noise on every revolution. Still couldn't work out the cause so I called for recovery (first time I'd ever had to do so since I started driving at 17).

The guy arrived some time later, and after some prodding around discovered that one of the spark plugs had come out (middle plug on the passenger side).In doing this it had also wrecked the lead, so no chance of a quick repair by replacing the plug. So the car was trailered to my folks' place and I used my BMW to get back home -- glad I've got two cars then.

So as it stands, hopefully I can just replace the plugs and leads, and it'll be OK. It's possible the thread has been damaged, in which case it'll need rethreaded first, but that's not really a big deal. My main fear is that part of the plug has broken and got into the cylinder, although the mechanic who recovered me said it's likely that the combustion chamber pressure would have blown it outwards. Just need to wait and see.

I'm quite surprised at this happening, the plugs were last changed about 20,000 miles ago so it's unlikely to have been caused by incorrect tightening. Has anyone else ever experienced such a thing? If so do I have anything to fear regarding damage to the engine?

I was planning on replacing the rocker gaskets and fitting new plugs and leads anyway so this will just hasten my need to do so -- probably next weekend if I can get the parts and the weather is good. Here's hoping it runs OK afterwards as I really don't fancy the prospect of having to remove the head.

Never seen or heard of anything quite like it  

Hopefully all will be fine upon replacing - give me a shout if you need anything ( hands / tools etc) as im not that far away in a v6  

[Craig_R]

Wow that is strange to happen.


Did the Plug just unthread itself or has it striped the thread out of the Head ?


Craig

[Paul M]

Cheers Markie, hopefully it will just be a case of replacing plugs n leads, which is a PITA of a job but one I was planning on doing anyway.

Wow that is strange to happen.


Did the Plug just unthread itself or has it striped the thread out of the Head ?


Craig

I don't know yet, it's quite difficult to see in there until I strip some stuff out of the way. I'm glad it wasn't the rear cylinder though, that would have been a nightmare as it's difficult enough to just change a plug on that one.

[Marks DTM Calib]

I have seen it on a 3.0MV6 following the fitting of a new spark with slightly over enthusiastic amounts of torque being applied.....

[Markjay]

According to GeffD (who used to work at the V6 plant and is a member here - and no doubt will reply if he is not in Afghanistan), spark plugs working they way loose was a common problem on the V6… though I don’t quite know why or what can be done to prevent this. His comment by the way was made on a thread regarding the new service interval increase from 40k to 80k – he said that the spark plugs may be good for 80k, but they will work their loose much before that…

Perhaps that’s why on the 2.6/3.2 the coil packs are bolted-on to the head – probably to retain the flying plugs…  

[Paul M]

Interesting! Hopefully that's all it is then, if it's worked loose by unscrewing then the thread should be OK.

I have no idea how tight they were installed, as it was done at a garage as part of a major service around 20k ago.

[Paul M]

Mark, while we're on the subject, can you still get  a good deal on rocker gasket kits? I need to change those before fitting the new leads as I don't want to fry them in oil. Ideally before next weekend but it can wait.

[Marks DTM Calib]

At the moment no.....Vx have put the prices up to....

[Paul M]

Damn, what's the current price? Typical VX, once they realise a component is a common failure they put the price up  

[JasonH]

I actually used a torque wrench to install my plugs, but one came a bit loose after a few thousand miles.

Installed by "hand" and they've been fine since.

[Taxi_Driver]

I havent seen a plug come out.....but i have seen the electrode of the plug come adrift and fall into the cylinder.....it made a horrible noise.....i thought to start with the bearings where going on the cambelt tensioner....it was a horrible cracking noise....it didnt seem to do any damage and was blown out of the exhaust valve.....well we assumed thats where it went as the noise stopped!

Iirc correctly vx recommend 25Nm for torquing down the plugs.....this imo seems very tight....and i have never tightened plugs this tight before.....somewhere between 17-20Nm seems adequate to me and plenty tight enough.....others might have other opinions  :-/