Vehicle: '09 E93 335i
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.
TIP: Love my GearWrench electronic torque wrench plus angle....