I found this bolt head under my car on the floor of my garage. There was also a small rust stain that must have dripped from where the head broke off. The stain was on the driver side just inboard of the left front tire. I haven't had a chance to get under the car to look around yet. The bolt head measures 19mm. Anyone know what this is? My CX-9 is a 2018 with 47K miles.
2016~2023 Help identify bolt that fell out of my CX-9!
- Thread starter mowyang
- Start date
Jack Rabbit
Banned
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- 18 Mazda CX5 AW
Yes. There are some on the front undercover, one that connects one plastic cover to another cover, one on the oil filter panel as well as one or two on each wheel well/fender liner. I had all these plastic covers and fender liners off and there are quite a few bolts.
Check all these locations to see if it is just a non-critical bolt that holds plastic panels. Otherwise look to make sure it's not something more serious.
A 19mm bolt to hold on plastic panels? Is that the size of the socket that fits on the hex or the overall diameter?
A 19mm hex nut is more typical of something that is torqued to a high value (like a drain plug or suspension bolt). If it was near the tire, I'd take a look at the strut at that corner.
A 19mm hex nut is more typical of something that is torqued to a high value (like a drain plug or suspension bolt). If it was near the tire, I'd take a look at the strut at that corner.
19mm is the size of the socket that fits the bolt head. To me it also seems too large for holding the plastic belly panels.
Unfortunately, the car was driven out of town before I realized this could be a safety issue. It's at my daughter's house about 80 miles away. It's been driven about 125 miles since I found the bolt.
Unfortunately, the car was driven out of town before I realized this could be a safety issue. It's at my daughter's house about 80 miles away. It's been driven about 125 miles since I found the bolt.
Jack Rabbit
Banned
- :
- 18 Mazda CX5 AW
Maybe it is...But a control arm bolt shouldnt rust out after 4 years.
I have 14 year old Fords still with their bolts.
If the control arm bolt was broke then it had to be sheared off by an impact and the arm possibly bent. The driver should notice the car veering to one side or vibrations, etc. And should have felt something was wrong before noticing the bolt...
Or Mazda is using sub-standard bolts that rust out after 4 years that is a safety factor and a big concern.
Hopefully it's not the control arm bolt.
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The piece I found does look identical to the one in the picture posted by e2jankow, right down to the rust. Looking at the diagram of the control arm assembly, there are several bolts (#'s 5,6,7,9) with the same type of head, any of which may have sheared off. Since the shank of the bolt may still be intact, that may explain why I haven't yet experienced a catastrophic failure. If the bolt is a horizontal bolt like #9, it may still be keeping things together. Just barely.
Jack Rabbit, agree with you 100%.
Many thanks for the help.
Jack Rabbit, agree with you 100%.
Many thanks for the help.
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#9 are the lower strut bolts. #5 doesn't have enough shear force on it, in my opinion. I've swapped control arms on my old 17 CX-9 and I believe it is bolt #7. It is the long bolt attaching the rear bushing to the frame. You can see it looking under the car from behind the front wheel. When I swapped mine last year, there was rust on it so I replaced it. There is room in the rear bushing holder for water to accumulate. #7 was the only bolt rusted, besides the ball joint, when I replaced my front suspension.
Thanks. Rust on the bolt is common? Sounds dangerous. If the bolt hadn't fallen off in my garage, I'd never have known there was an issue. I'm going to have the car towed to a shop; your info will help me direct them.
Should I have this looked at by a Mazda dealer specifically, or is taking it to any reputable shop OK? Would this be covered by any warranty?
Should I have this looked at by a Mazda dealer specifically, or is taking it to any reputable shop OK? Would this be covered by any warranty?
Jack Rabbit
Banned
- :
- 18 Mazda CX5 AW
Not sure about rust.
If it's underbody panel cover bolt, then yes they cheap and could rust.
If it's a control arm bolt, it had to have been sheared.
Local mechanic would be able to find the problem. No warranty, your bumper to bumper is likely expired
Probably need to get the bolt from a dealer, and they likely don't stock it. The replacement needs to be the correct thread and length as well as the correct strength. A standard high strength bolt of the correct thread and length plus a flat washer under the head should work. Anything torqued to 175 or 120 lbs-ft is substantial. Getting the broken part out might be a real challenge.
Is this car safe to drive as it is? I'm not at all sure.
https://www.engineeringtoolbox.com/steel-bolts-metric-grades-d_1428.html
Is this car safe to drive as it is? I'm not at all sure.
https://www.engineeringtoolbox.com/steel-bolts-metric-grades-d_1428.html
After looking at the picture of the bolt a bit more, I would suggest you have the mechanic check the other similar bolts on you car. The corrosion pattern on that head indicates that a majority of the cross section of the shank of the bolt had been cracked for a while. The crack allowed water into the shank of the bolt and corroded the metal. The bolt would not have been able to rust the way it did if the bolt had failed suddenly - the fracture surfaces would be free of corrosion. Bolts don't normally fail at that location unless they were under torqued or had a flaw in the bolt introduced during the manufacturing process.
I'd ask them to check the other bolts. Remove them, look for corrosion, and retorque or replace any that look questionable.
I'd also report this to Mazda and NHTSA. If there was a bad batch of bolts used it would help to get reports on file.
I'd ask them to check the other bolts. Remove them, look for corrosion, and retorque or replace any that look questionable.
I'd also report this to Mazda and NHTSA. If there was a bad batch of bolts used it would help to get reports on file.
That’s good that nothing else was rusted. You may want to have the other control arm bolt replaced as well. There have been 2 updated part numbers since the first version of that bolt. Please let us know how they removed the bolt shaft and how much they charged.
Jack Rabbit
Banned
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- 18 Mazda CX5 AW
I've never seen anything like that my entire life. A four(4) year old arm bolt rusted through ? Kinda messed up. You sure there was no impact maybe several months ago?
Amazing !
Guess I'll have to check em.
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- Mazda CX-9 Signature
Looking at the head of the bolt again, it doesn't seem to be untouched. The corners aren't sharp. I just have a difficult time believing the bolt would rust off like that.
Jack Rabbit
Banned
- :
- 18 Mazda CX5 AW
Hmmm. More you look at OPs first picture...you can see where it broke off...you can see clear delineation of outer circle but the inside(inner circle) is rusted almost like the bolt was defective and hollow inside. Like a hollow chocolate bunny...easy to break.
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- Mazda CX-9 Signature
I don't doubt there's a level of defectiveness to the bolt but it would not break off simply untouched. My theory is the bolt got over torqued and sheared the bolt 95%off its head. Only that 5% outer portion was holding it. Water got in and rusted thru. The head was finally detected from the vibration.
