About 10 days ago, the evening before leaving on vacation, my wife phones me and says that the engine in her mini is making a "banging" noise and she has pulled it over on the side of the road near our home.

Fearing the worst ( broken pistol, con rod etc) I went to have a look at it and found that the #1 spark plug had popped out. The threads on the plug were damaged and a new plug won't even start to thread. Had it towed home and now the fun begins.

I don't want to attempt a re-thread with the head still on the block but having never pulled a mini apart I'm curious if there are any surprises to removal, or things I need to be aware of before I take it off. It looks fairly straight forward but...

Any help/ info very much appreciated.

cheers,
RC

... I found the thread about the helicoil insert - I guess I might have to go that route?

 

The helicoil has been the first step for most folks faced with this issue. When done with care it's an excellent fix.

 

just take your time....

Matt

 

I have heard stories of blowing out plugs on boosted motors. Not sure if that's what you have. I occasionally get out the 'ol 5/8 socket, extension, and wrench and check them for that reason. Definitely something to do if you have a pulley upgrade, tune, etc.

If the plug won't go in, at least consider retapping the spark plug socket if the remaining threads appear to be intact. With either that or the helicoil approach, if you do choose to leave the head on, be mindful of shavings falling into the combustion chamber. Have a small light and a long, thin magnet handy with a flexible head on it.

The one thing that comes to mind is to make sure to mark where the sprockets line up for the timing chain. You can even rotate the assembly to get the marks to line up (all sprocket gears should have them). Reference a Bentley manual if you have one (or go buy one).

 

The best trick I heard was to put some panty hose in the cylinder. When you tap the head, the shavings stick to the panty hose when you pull them back out!

Pretty cool, huh?

Matt

 

Dr Obnxs... good tip!

 

Thanks guys. It's a non boosted engine with no mods- kind of surprised me that the plug came loose as the others are still tight (I retorqued them anyway) A new plug wouldn't thread and when I put a bore light down there I can see thread so I'm going to try a retap first. I'll let you know how the pantyhose thing works out. I'm also going to rig a "straw" for the shop vac and try that too.

 

Update. Tried the re-tap but there isn't enough thread left to hold the plug tight.

Ended up having some one put in a helicoil- it's all good now.

RC

.... all work done with the head in place.

 

Thanks for the update.

 

glad to hear it all worked out for you. After I had a plug pop out of my car, I also had a heli coil installed with the head on and it got back up and running but ever since then I've had a severe hesitation past half throttle happening in all gears. Its been very frustrating and I cannot figure out what it could be. Anyways just glad to hear it all worked out for you. Some of us (well at least me) haven't been as lucky

Steve

 

what you need is a Time-sert.

http://www.timesert.com/

 

I have a Big-Sert kit with a 16.8mm insert for sale if anyone needs it to repair a blown out helicoil. It's only been used once.

 

I dont know if that was at me but I messed up my terminology, I had a time-sert installed as well, my mistake

 

I meant it for the original poster. Sorry. I should have explained a bit more.

Time serts are a little different than Heli-coils. Heli-coils are good for low stress applications, but not what I would use for a spark plug. A Heli-coil uses a coil of threads with a tang at the end that must be broken off. You would then have to retrieve the tang and also the metal from threading the hole from inside the cylinder.

A Time-sert is a self-locking solid insert. They work very well under compression and expansion forces. In the Porsche world, they are commonly used for head stud repair on 911 aluminum and magnesium engine cases. As the engine ages, the head studs heat cycle and expand, til eventually it snaps, or it strips out of the case. During rebuilds, they replace the stud and Time-sert the hole for added strength.

I helped a friend fix a stripped out glow plug on an old Mercedes diesel. A lot more compression than the MINI's engine and it works fine.

As for Vernon,

I would maybe do a compression check on the cylinder. See if it's within range of the others. Does this happen when the engine is cold? How long has it been happening? Codes thrown?

 

Actually there is a specific helicoil for spark plugs. They are solid inserts, not coiled, and don't use a tang. There is a tool to push the upper-outer threads, which are ribbed, into the head to hold it in place. Not really ideal, but works as a temp fix. Here is a picture:



I personally would no trust a helicoil for the sp hole, I would go straight to a Time-Sert. It's light years ahead of the Helicoil. Cuts a new seat, no way of it backing out. It's really ideal.

 

Learn something new every day. The locking method on that seems less than ideal. Seriously though, the Time-sert is well worth it.

 

My R53 just blew out #2 spark plug today at the track. I really don't want to take the head off, but I don't want shavings in the engine, either. I will tell my mechanic to use the panty hose trick referenced by Matt (Dr. Obnoxious) above, and will probably go with the Time-sert. Car only has 32k on it, and a total of about 20-25 track dates. Plugs were not changed that recently. What is the proper torque for them?

 

Proper torque is 18-21.6 ft-lbs.

 

22-25 ft-lbs....

Matt

 

I had a time sert put on cylinder 2 last week at a local machinist referred to me by the dealer. I was looking at the engine yesterday for the first time since the job and noticed that the boot on cylinder 2 was sticking up. I feared the worst that the spark plug had blown out again (my car had just put itself in limp mode). However when I went to push the boot down, I noticed that it was already clicked onto the plug. And it just seemed as if the spark plug was sitting higher.

Is it normal for the spark plug to sit higher up after a time sert job? It seems odd to me. I called and asked the shop and they said bring it in and they'll take a look Friday.

Thanks

 

plasticknives,
Do you still have the Big Sert 5141S for sale?
"I have a Big-Sert kit with a 16.8mm insert for sale if anyone needs it to repair a blown out helicoil. It's only been used once."
Thanks, Mike