I was out on a nice solo canyon run when I heard some loud thumping and the check engine light went on. I checked under the hood and saw nothing out of place. I drove a little farther and it happened again. All in all after an hour and half wait and a tow home, I checked under the hood a third time to see a spark plug lying on top of motor. Upon arriving home, I attempted to replace plugs and three went in fine and the fourth appears to have been stripped. I've seen some posts on this topic-any newer posts or suggestions. I'm at 58K and using the dealer is not an option. I may have it towed and checked out by my regular MINI tuner-Mick Brown.

 

How does the plug look? Does it appear that it hit (or was hit by) the piston or valve? How do the threads on the plug look? Will a new plug thread into the head? Just trying to determine whether its the plug or that cylinder head. If it is just the plug, that is a simple and relatively cheap fix. If it's the cylinder head, you need to make sure there is no other damage. There must be some reason that caused such a failure. Try to determine what it is.

If it is the head, have you considered heli-coil? I know of a great cylinder head shop in Oakland that may be able to help.

Give me a call if you want to persue.

Hope this ends up being something simple.

 

What type of plugs were you using?

 

I used NGK plugs and the thread actually appeared ok on the stray plug-that is why I'm puzzled. Attempts at using a new plug did not work. I came across heli-coil in some posts, I'll see what my local guy can determine. I'll call you norm as I get more info.

 

Local mechanic determined that there was no thread left in the problem spark plug hole. Attempts at heli-coil will be done today-hopefully w/o removal of head. Spoke with dealer and rep claims aftermarket plugs are the cause and a repair was done recently for $5000 (rebuilt head). I was warned about using aftermarket plugs in the future. Any one else consider this a valid statement/cause? More to follow....

 

Sando,

Make sure they get all the metal that is left behind from machining out the damaged spark plug hole. If any of that gets down the cylinder between the piston and cylinder it will cause some further damage. That's the big risk in not removing the head.

Here are some websites/pages that may shed some light on the problem:

http://www.globalspec.com/FeaturedProducts/Detail/MetricScrewTool/Helicoil_Spark_Plug_Thread_Repair_Kit_14mm_x_125/23773/0

http://www.emhart.com/products/helicoil.asp?gclid=CNnssf2cu4wCFQwzZAodKwNOaw

http://www.type2.com/library/engineg/sphl.htm

http://www.xs11.com/tips/repair/repair27.shtml

http://www.timesert.com/html/faq.html

If you are unable to accomplish repairs with the current shop, I will give you then name of the head shop I use. They are in Oakland and can fix anything.

Good Luck and keep me posted

 

This sounds odd to me.
If the plugs were misfiring or something like that, I might buy into the statement about aftermarket plugs. But if the plug is the right size for the engine, there isn't a lot that can go wrong with the threads. IMHO

 

It's my understanding that the "complaint/flaw" is that the aftermarket spark plugs have a different (lesser) torque and that they work loose. Once that happens the threads start to deteriorate.

I am not sure I buy into this arguement. I could see it if the sealing gasket for the spark plug has inadequate "crush" which allows the plug to loosen.

If the aftermarket plug has the proper thread size and "cut", then they should use the same torque value.

This may have been an unlucky isolated incident where one plug was just not tightened enough and worked itself loose. If this were a design flaw I would figure we would see a lot more failures reported.

 

There have been quite a few instances of aftermarket plugs blowing out. Nobody seems to know why, but they do.
Here is one example, and the responses to it.

Check plug torque monthly.

 

If you do a search on this topic, about 95% of the cases are with aftermarket plugs.
I'm not really sure why, but that's what most people have reported.

 

Thanks you guys! All good input.

Partsman,

Is it ALL aftermarket plugs or just certain brands?

Eric,

I assume that checking torque monthly goes for either aftermarket or OEM plugs.

 

yep, aftermarket plugs are likely the culprit.....Mary more blown plugs are the densos but it is a pretty well established issue with aftermarket plugs!

Personally I would like to know what exactly what material is being used for the plugs. my theory is different coeffecients of thermal expansion in the materials used in aftermarket plugs is causing more stresses and the cyclic heating and cooling of the engine is causing failure

 

There are only a couple different brands the guys use on here, I think i've read about it happening with either brand.

If you(or Eric) don't mind me addressing your last statement, it is good practice to check them periodically. Although, i've been running the JCW plug and have never had them come loose.

 

I've got OEM and just check every couple of months.
Given all the reports of blown out plugs, if I had aftermarket, I'd check them monthly. It's quite a pain if you've got a large IC, but doing a helicoil is even moreso!!

 

thanks for the continued info and insight. Much appreciated! I'll let you guys know the outcome.

 

BACK ON THE ROAD!!! Heli-coil was attempted/completed and I'll go from here. I was warned to be cautious at first. My Jackson plug wires were replaced as well they were in poor condition after 1 year. I went with the same type NGK plugs despite dealer's claims. Thanks again for the tips. All for under $300 bux! Thanks to Mick Brown and his shop.

 

Had the same thing happen to me last night!! Guess what plugs I was running?? Denso IK22's!!!! What's really annoying is I installed them about a month before this thread started! 15,000 some odd miles and just shy of two years later look what happens! How did I miss all this information?? There were no tell tale signs that they were coming loose, just POP out of nowhere and no more threads. I had it towed to the Mini dealer but judging by you guys experiences it doesnt look like they are going to cover this and a heli-coil is the recommended repair procedure. I guess I'm gonna go back to stock plugs or maybe try Brisk's (seem to be of racing quality). I'm lost at what to do now. I'm running the Alta 17% v2 and would like to get a RMW tunne sometime this year so I figured I'd almost have to run a different plug. Any ideas??

Steve

 

anyone care to shed some light on this? I think I'm going to start running JCW plugs, at least those are from BMW and if anything was to happen again it won't look so bad. I'm definitely going to start checking them regularly now! What an unfortunate part of owning these finicky cars!

 

Well a year and half later and I'm still motoring on replacement plugs. No problems just had 75K service at local shop who saved the MINI from plug incident.

 

Thanks for the update man....very reassuring to hear. I had a time-sert installed on mine the other day. Have you done any autocrossing, track days or dynoing since the install? I'm just hoping that the high rev's won't do any damage to the insert.

 

You GOTTA TORQUE all these plugs no matter what brand to 22 foot lbs.................

I get a sense from reading all the threads here that owners are afraid of stripping the threads and therefore not giving that plug that extra 1/4 twist/turn needed to seat the plug washer.

But it's also never a bad idea just to re-check them every oil change....along with your power steering pump cooling fan.

 

NGK is NGK ! They are not re-tooling their equipment at NGK just to make a single line of plugs for MINI JCW's - They probably fit in some chevy's too.

It's apparent these issues are from improper installation rather then thread tollerances of each plug....

 

You guys have just convinced me to return my aftermarket spark plugs and to keep running my OEM. lol

 

If they are Denso take them back.

 

The same thing happened to me on wednesday my spark plug blew out of the motor.
I took it to the shop 300.00 later I got the car back with a helix the mechanic told me that when changing the plugs leave it to cool for 24 hours if you change them while the motor is hot you will stretch the threads.