2016~2023 Help identify bolt that fell out of my CX-9!

[GTEyes]

Yeesh, 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.

 

[mowyang]

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:

There have been 2 updated part numbers since the first version of that bolt.

How is this indicated? Does the current part number sequence somehow indicate a version number?

 

[jal142]

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?

You can look up the part number on one of the online parts stores. Some or most of them will list the superceded part numbers. There is not an obvious way (at least that I'm aware of) to determine the part revision from just the current part number.

 

[e2jankow]

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?

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

 

[mowyang]

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

According 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?

 

[Jack Rabbit]

Yeesh, 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.

One woul

According 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?

Yes

 

[mowyang]

To close the loop on this, the dealer replaced the broken bolt and the matching one on the other side. They inspected but did not remove the other bolts.

Mazda agreed to cover all costs.

The shank of the bolt was easily removed. It was so loose that the tech could twist it with his fingers.

Thanks again, everyone.

 

[Silly Wabbit]

That debunks my theory if the bolt being over torqued. Thanks for the update!

 

[roundle1979]

Glad you had this resolved.

I notice that the service manual suggests to 'tighten chassis bolts' ever x number of miles. I doubt that anyone does this. If they did, seems like they may find a few that are missing.

Question for OP: Did you notice any difference in driving characteristics after the bolt fell out?

 

[mowyang]

No, the missing bolt head never had an effect on any driving characteristics that I noticed.

 

[PTguy]

That debunks my theory if the bolt being over torqued. Thanks for the update!

Maybe not. Once the head broke off the bolt the forces were removed. Most likely, of course, is that the bolt was defectively manufactured.