[CALWATERBOY]

Vehicle: '09 E93 335i

Disaster! I cross threaded the mounting bolt for a M3 Guide Rod at my 3's Bearing Carrier!



After a lengthly bout of execration, steely calm engulfed my wah.


I knew what must be done: Travel, to Napa Auto Parts, there to select a M12 x 1.5 [12 mm fine thread, blue pkg] Helicoil installation set.




Returning to my ride $80 lighter - Amazon much less but preferred not to wait - angst caused beads of sweat to form.....it was a warm day.....and I had never done this before....

First things first. Verifying that my mount bolt was spinning freely, this job did not require drilling out the threads. Some jobs do -- but my bearing carrier threads were completely stripped out.

I removed the bolt - had damaged threads near the tip which crunched & munched all bearing carrier threads going through. Only when the bolt was fully 'threaded' in did I find it could not be torqued! Nothing left to torque against.

Ran a cylindrical magnet through the hole - came out with a large ammt of shredded thread, leaving the hole more or less clean.

I inserted my tap into an Irwin adjustable tap socket, Home Depot, to cut threads into which the Helicoil will thread:




The tap supplied is of the self-guiding type. Just start it in the hole....




....and ratchet until the tap has cut all the way through:




Then, the Helicoil, shown here with plastic install tool and threaded metal shank to thread the Helicoil into the hole:




Drop a Helicoil tab first into the plastic installer....




Insert the threaded shank....




Turn shank until a thread or two is exposed. Tab should be at the tip:




Blow compressed air through the hole w/newly cut threads to remove debris.

Insert Helicoil tip into hole to be repaired and, holding the plastic installer with a wrench, turn the shank, thus threading the Helicoil into the threads you've cut for the purpose:




When the Helicoil's fully installed, thread the shank out, leaving the coil in:




The tab can be punched off, or left in for the bolt to snap it off as I did:




When the mounting bolt's ratcheted in, it threads into the Helicoil which is designed to press against the threads cut with the tap. Result: Successful repair - a new bolt torqued normally to 100 N/M +90°


I used Permatex 81343, Ace Hardware, on the threads.




Job done!


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TIP: Love my GearWrench electronic torque wrench plus angle....
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[smellfish]

Solid write-up! I stripped a water pump bolt on my old SR20 build. After I changed my underwear I used one of these kits, problem solved.

[Mauryk]

Great write up!

[warpig666]

Great write up. Hopefully I will never have to use it. I think having to re-tap/thread a bolt hole (especially a hard to reach one) has to be one of the most disappointing, aggravating and frustrating things ever!

[jeguth1s]

Thanks for this! I did the same stupid thing this weekend. I had to drill out my hole though. The hardest part was sourcing a drill that would fit in there! I did the other guide rod which is harder to access. Luckily 5 trip to home Depot later, I found the perfect drill. Also, 31/64" is the correct drill bit to use. Don't expect to find that at Home Depot or Lowe's either.