There have been 2 updated part numbers since the first version of that bolt.
A defective bolt is my conclusion also. I agree that the rust across the entire shank shows that the bolt had been cracked for a long time, perhaps since the car was manufactured. I'd not considered an over or under torquing of the bolt could have created the defect. Wouldn't robotic manufacturing prevent such mistakes?
I plan to have my service guy replace the matching passenger side bolt as well, citing the likelihood of defective bolts.
This is very interesting info:
How is this indicated? Does the current part number sequence somehow indicate a version number?
A defective bolt is my conclusion also. I agree that the rust across the entire shank shows that the bolt had been cracked for a long time, perhaps since the car was manufactured. I'd not considered an over or under torquing of the bolt could have created the defect. Wouldn't robotic manufacturing prevent such mistakes?
I plan to have my service guy replace the matching passenger side bolt as well, citing the likelihood of defective bolts.
This is very interesting info:
How is this indicated? Does the current part number sequence somehow indicate a version number?
According to one of the parts sites, that bolt is used in these positions:I'm not sure why Mazda added different part numbers for the same bolt. I assume it's due to either an upgrade or new manufacturer.
These are the part numbers I've found for this bolt:
- 9YA0-11-401, 9YA0-11-401A, 9YA0-11-402
One woulYeesh, glad you got this figured out. Sorry I lead you astray with my guess. The 19mm head really was the indicator that this wasn't a minor bolt.
YesAccording to one of the parts sites, that bolt is used in these positions:
Left Outer, Left Lower, Left Rear, Right Outer, Right Lower, Right Rear, Rear Outer Outer, Rear Outer Lower, Rear Outer Rear
Does that mean there are nine separate places that bolt is used on the CX-9? If there was a defective lot of bolts, could it have been installed in each of those places?
Maybe not. Once the head broke off the bolt the forces were removed. Most likely, of course, is that the bolt was defectively manufactured.That debunks my theory if the bolt being over torqued. Thanks for the update!