Mazda Rear Subframe Rot - Pics

G

GMFan

Joined
Dec 26, 2007
Messages
2,534
Location
NC
Hey all,

Attached are some pictures of the rear sub frame on my '11 Mazda6.

The front sub frame was replaced by the dealer about 6 months ago as it was rotted out - this was covered under a recall so all work was done for free. Apparently the coating applied at the factory wasn't sufficient for corrosion protection. However, I also have rust on the rear sub frame - for which there is currently no recall on this. To me it looks like there was a similar fault in the factory for the rear sub frame as well. Question is how bad does it look? Car has 140k miles and runs great.

Is this something I need to get addressed now or can I let it be and get a few more years out of the car? The main thing that concerns me is the cracking. Thanks.

Pics
 
No rust prevention products will protect that. By the looks of it you'll get one more winter out of that rear subframe. I wouldn't be surprised if it falls apart after hitting a jaw shattering bad hole in the road to be honest. What's crazy to me is the rest of the suspension doesn't look that badly rusted! Must have been improperly painted/protected from the factory like you said.
 
Sad to see this; I'd heard that the Mazda rust problems ended c. 2009. In 2013 when I was last shopping for a vehicle, a Mazda salesman told me the last rusty year was '04 or '05, but since then I've seen later Mazdas, at least up to MY '09, with the rusty rear wheel wells.

Hopefully that subframe is an anomaly.
 
I bought brand new in March 2011. I lived in upstate NY where winters are brutal. I moved down to NC in 2015. I think a combo of faulty finished sub frame and 4 years set the cancer in. My Dad has a 2003 Chevy Trailblazer that has less rust that this car. I owned GM cars up in NY which never rusted out like this.
 
Car was assembled in Flat Rock, MI in Ford factory. This car is basically a Ford Fusion. I figured the rust wouldn't be an issue since it was built in a Ford factory instead of Mazda factory. Bad luck of the draw with faulty sub frames. Based on what you all see am I okay for a while or does it need replacement. Thanks.
 
Did you buy that car used? Did it come from the rust belt? Do you live near the coast? Rust buckets from up north frequently end up on used car lots down south. That car is nearing the end of it's useful life.
 
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You'd have to have it blasted and see what is left to see if it's really still suitable for use
 
Originally Posted by GMFan
Car was assembled in Flat Rock, MI in Ford factory. This car is basically a Ford Fusion. I figured the rust wouldn't be an issue since it was built in a Ford factory instead of Mazda factory. Bad luck of the draw with faulty sub frames. Based on what you all see am I okay for a while or does it need replacement. Thanks.


While it may have been built right along side with the Ford Fusion in a Ford plant, my guess is Mazda still supplied numerous parts for its own vehicles and this might be one of them. Ford just assembled it. From what I've gathered the Fusion doesn't have this rust concern.

Inspect it, get a metal hammer and tap around on the suspension lightly to see how deep the rust is. Do you plan on keeping the car? If so then I personally would drive it for another year and this time next year I'd get the sub frame replaced. However, I'm not sure how cost effective it will be.
 
I dunno why exactly, but most of the vehicles I see with frame rust that is so aggressive as that have an origin in Japan. Having said this my '99 Camry - origin Japan (not Kentucky) is well nigh corrosion free on its subframes. However it has lived its life here in temperate Vancouver.

I have to think that subframes that rust like that ARE NOT simply due to a lack of proper prep / phosphating / e-coat... but rather due to improper steelmaking. The Japanese are amongst the best steelmakers - for pipeline steels,,but for low grade structural like this - generally I believe turn out poor materials. Others?
 
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Originally Posted by Cdn17Sport6MT
I dunno why exactly, but most of the vehicles I see with frame rust that is so aggressive as that have an origin in Japan. Having said this my '99 Camry - origin Japan (not Kentucky) is well nigh corrosion free on its subframes. However it has lived its life here in temperate Vancouver.

I have to think that subframes that rust like that ARE NOT simply due to a lack of proper prep / phosphating / e-coat... but rather due to improper steelmaking. The Japanese are amongst the best steelmakers - for pipeline steels,,but for low grade structural like this - generally I believe turn out poor materials. Others?




This car is not from Japan.
 
It's a coating issue more than a steel quality issue.

I see a lot of vehicles where the painted body metal (floors) on the underside looks good and the adjacent subframes are corroding badly.
If the mfgrs used the same level of paint prep and application, those subframes would look good too.
But because the subframe material is thicker, they don't think it's necessary / don't add the cost.

If you live in the rust belt and want to avoid this problem, you need to be spraying on the fluid film or woolwax every fall. Same thing with pickup truck frames.
 
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Our '14 Focus' rust is awful. The front subframe is rotting along the leading edge and where the felt undertray holds moisture against the subframe. The rear trunk lid is totally rotted. It's total crap.
 
my Mazda6 spend first two years in NY state, and another 10 in Ga, and all around is still in great condition

sorry that you need to deal with all that cost on yours
 
Originally Posted by PimTac
Originally Posted by Cdn17Sport6MT
I dunno why exactly, but most of the vehicles I see with frame rust that is so aggressive as that have an origin in Japan. Having said this my '99 Camry - origin Japan (not Kentucky) is well nigh corrosion free on its subframes. However it has lived its life here in temperate Vancouver.

I have to think that subframes that rust like that ARE NOT simply due to a lack of proper prep / phosphating / e-coat... but rather due to improper steelmaking. The Japanese are amongst the best steelmakers - for pipeline steels,,but for low grade structural like this - generally I believe turn out poor materials. Others?




This car is not from Japan.


I'm not sure a person can say that the subframe is mfr'd in - (and steel sourced in) North America versus Asia or elsewhere. The car assembly was in North America.

What I'm saying is that some steels seem to corrode at a muted pace; other steels absolutely horribly corrode. I've seen more North American steels in the former category.
 
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