spark plug threads in head stripped out

[FD'93-525iT]

Wanted to post my experience with stripped spark plug threads in the head. I had a spark plug (second from the front of the engine) that worked it's way loose a month or so ago. I replaced the plug and tightened accordingly but it happened again the other day and upon inspection, no more spark plug threads in the head. I initially called a couple of reputable mechanics that mentioned pulling the head, sending to a machine shop, etc., but with estimates starting around $1500 (US), I decided to look for a different answer. Searched here at BimmerNut and found info for helicoil procedure and thought I'd give it a try. Bought an OEM Fix-A-Thread Spark Plug Repair kit from Autozone and was ready to give it a try when I realized that the top of the tool uses a 3/4" socket but, as many of you may know, a 3/4" socket won't go down the spark plug shaft! So... went to my trusty grinder and reduced the top of the tool so that a 5/8" socket would fit the top of the tool (5/8" will fit down the spark plug shaft). After that, it was a breeze. Tapped in the new larger threads, inserted the new set of threads that came with the kit, used the included tool to expand the top of the new threads, put in a new plug and the car runs as before. This was a first for me as far as modifying a tool, but everything worked out great. Hope this helps someone along the way.
I have a 1993 525iT with 200,000 miles.

[Rus]

Be careful removing the plug from that cylinder in the future. I did a similar repair on my 535i and at the next plug change, the insert came out. I didn't flare it out enough and didn't really have room to swing a hammer in that area at all. No real harm done, just inconvenient. Just swapped the sleeve and put a dab of black silicone on it (I believe that is what the instructions recommends) before installing a new plug. Just my experience.

[Grantus]

Did you remove the head to do this repair? If not, how did you prevent the aluminium from the tapping procedure from falling into the engine?
Did the helicoil have a snap off end?

I remember a friend doing this years ago on a well worn Jaguar without taking the head off. He used a grease soaked rag down the plug hole and gently retrieved it with bits of alloy attached after tapping .

[Rus]

You catch the aluminum bits by packing the flutes in the tap with grease and then cleaning it periodically. Any bits that do end up getting into the chamber are more likely to be blown out of the exhaust valve than to be lodged between the piston and cylinder wall. The helicoil itself is not a snap-off type. It is essentially a thin metal cylinder with threads on the inside and outside. It is threaded into the head and secured with a special flaring tool that comes in the kit.

[Ross]

Good that you were successful. Shameful that the "reputable mechanic" is not so resourceful or has his customer's best interest in mind.
I second the nod to be careful in the future with that hole. I use a small bit of copper anti-sieze paste on spark plugs into aluminum heads. Be careful not to use too much and chasing the threads is a good idea when changing plugs too, this removes built up carbon or anti-sieze paste. Silicone on spark plug threads is a bad idea. And never remove plugs from aluminum heads on a hot engine unless you want more practice with the Heli-coil kit..

[FD'93-525iT]

Did you remove the head to do this repair? If not, how did you prevent the aluminium from the tapping procedure from falling into the engine?
Did the helicoil have a snap off end?

I remember a friend doing this years ago on a well worn Jaguar without taking the head off. He used a grease soaked rag down the plug hole and gently retrieved it with bits of alloy attached after tapping .

I sprayed some carb cleaner into the cylinder after the tapping procedure to flush the shavings back out of the spark plug shaft.

[Rus]

Good that you were successful. Shameful that the "reputable mechanic" is not so resourceful or has his customer's best interest in mind.
I second the nod to be careful in the future with that hole. I use a small bit of copper anti-sieze paste on spark plugs into aluminum heads. Be careful not to use too much and chasing the threads is a good idea when changing plugs too, this removes built up carbon or anti-sieze paste. Silicone on spark plug threads is a bad idea. And never remove plugs from aluminum heads on a hot engine unless you want more practice with the Heli-coil kit..

When I mentioned using silicone, I was not referring to regular spark plugs installations. When a helicoil insert is installed, the instructions tell you to use a silicone sealant to install the insert. The plug is installed as per normal procedure.