Mazda Rear Subframe Rot - Pics

[GMFan]

I think the front sub frame was a North American manufactured part as the company and Part # were identified in the recall report. Not sure if the rear sub frame was sourced from same supplier but it's a bit ironic they both have similar corrosion features.

 

[Amkeer]

This is why Fluid Film is important. Even here in the South my vehicles are coated once or twice a year. I would say those parts need to be replaced.

 

[Eddie]

Almost appears to have been driven in salt water on the coast.

 

[Delta]

Musta been the same place that made the Toyota Tacoma frames... Lack of proper corrosion protection applied, rusted them out real quick.



Ugh, I just made myself sad thinking about it...

 

[Cdn17Sport6MT]

Originally Posted by Amkeer
This is why Fluid Film is important. Even here in the South my vehicles are coated once or twice a year. I would say those parts need to be replaced.

Seems to me that Florida particularly has a lot of humid, salt-laden air. Not quite sure how salt could be entrained in the air - but I'm told it DOES affect corrosion rates.

 

[kschachn]

Originally Posted by Cdn17Sport6MT
Seems to me that Florida particularly has a lot of humid, salt-laden air. Not quite sure how salt could be entrained in the air - but I'm told it DOES affect corrosion rates.

Florida is humid, so a high dew point and they are near the ocean of course. The moisture in the air can dissolve or make a hydrogen bond with sodium chloride just the same as in a glass of water. If you're close enough to the ocean you can taste it in the air.

 

[supton]

Call me crazy but IMO if you are now in the south then I'm going to wager that it'd last several more years, even doing nothing. It looks bad, it'll look worse, and it'll be no fun to work on. But if you've seen some of the heaps that ignore reality and roll on... you'd realize, that not that bad. Especially if you just want to get a couple more years out of it, then toss.

Even if I'm wrong... is it worth saving? Effort spent vs replacing with something else.

 

[2004tdigls]

Originally Posted by GMFan
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


your rust problem in the 6 series is not unique, the 3 series cars are virtually biodegradable

https://www.mazda3revolution.com/threads/rust-rust-and-rust.205994/

https://www.mazdaforum.com/forum/mazda3-26/04-mazda-3-rusting-around-wheel-wells-10954/


just don't buy a Mazda again

 

[KGMtech]

As TRAV said, have the rear subframe treated to remove the loose flaky rust and then get it coated in something really oily and waxy. It's not too late. This is not a steel issue as much as it is a post welding - pre painting problem. The e-coat applied to the welded assembly was sub-standard for coating film thickness, or the phosphate dip process did not create the right phos crystal base for the black paint to stick to.

 

[GMFan]

Thanks for all of the replies.

I'll take a closer look this week and give it a thorough inspection and poke around to check for any holes. If all looks good I'll maybe do the wire brush where I can get to and apply some protective coating.

The car is worth $3,500. Not sure what it would cost to replace this if I had to. The car runs good so I think if I had to repair now it would be worth it to get more life out of the car. Thoughts?

 

[Kurtatron]

Originally Posted by supton
Call me crazy but IMO if you are now in the south then I'm going to wager that it'd last several more years, even doing nothing. It looks bad, it'll look worse, and it'll be no fun to work on. But if you've seen some of the heaps that ignore reality and roll on... you'd realize, that not that bad. Especially if you just want to get a couple more years out of it, then toss.

Even if I'm wrong... is it worth saving? Effort spent vs replacing with something else.


I agree. I have see so much worse in the Midwest. It will be suicide to work on it, but to drive it? I think it is safe enough.

 

[Cdn17Sport6MT]

Some work with a screwdriver may just poke a hole in the cracks.

I'm still not convinced it is only (or at all, for that matter) a pre-phosphating metal prep issue, or a phosphating- or e-coat issue... Steel that spalls-away in corroded layers like what I see there may be dirty steel, or poor steel quality / lousy steel grade/chemistry in the first place.

 

[SeaJay]

Drive it like you stole it. Despite the dire warnings and the fact that it isn't pretty enough looking for some of our posters I think you'll get a few more years of driving.

 

[GMFan]

Dealer quoted me $3,826.46 to replace and total repair is $4180.41 with tax. It would be hard to find a replacement car for 4,200 in same condition and well maintained. I'll have to evaluate how dire the subframe is.

If it lasts a few more years to limp along that may be the answer. If it needs immediate replacement maybe it is worth the repair.

There's always the chance Mazda will recall rear subframe like they did the front subframe and reimburse me - but not guarantee on that.

$2,726 parts, $1,000 labor and $99 alignment.

I may have dealer look at it now since car is still under 10years old. If it's deemed to be structurally unsound and needs replacement I wonder if I can convince them to work with me on the cost of repair. There's clearly some kind of QC issue on the subframes they put in at the factory. Otherwise Mazda is okay with

 

[Trav]

Its not that difficult to replace yourself but IMO its not that bad from what I can see, we see much worse than that. Clean it, needle scale or power wire brush it and see what you are dealing with.
Don't waste your time and effort spraying anything over scale rust. its a fools errand. If there are no holes you can go with a coating like Noxudol alone or use an epoxy rattle can paint that is self etching like frame paint from VHT or a product like Rustbullet then noxudol over that once its dry.

https://www.rustbullet.com/product/rust-bullet-automotive/

 

[GMFan]

It's been raining for what seemed like 3 weeks straight. Today I finally got a change to get under the car and take a closer look at what I'm dealing with. I used a flat head screwdriver and probed around. It appears that in many places the rust is the outer "layer" of the steel which includes the protective paint coating. In some cases it appears there are a couple of rusted "layers" and it falls off fairly easy with some prodding. In the picture below - you can see what I am talking near the drain hole.

I confirmed by banging on the frame with the screwdriver that the structures are still strong and there were no rust holes found.

Would removing the rust and using a product like Rustoleum help stave off the rust? Another option I saw was Corroseal Rust converter - this product you paint onto the light surface rust and it bonds with the rust to create a type of black primer. http://www.corroseal.com/

Any suggestions to treat this? Thanks.

https://drive.google.com/file/d/147JfqE_-mFQg2IMRyrfVqhtKkHuLrsP5/view?usp=sharing

 

[GMFan]

So today was the day I was going to apply POR15 to the rear subframe to stop the rust. I had purchased degreaser, metal prep and the POR15.

This morning I took a wire brush and started getting the rust off. Around the rear shock towers I punched through the frame and there is a large hole.

I can't imagine this doesn't compromise the structural integrity of the frame. Is it worth rust coating at this point or is it new rear subframe time? Thanks.


https://drive.google.com/drive/folders/1ciRsffJIt9JD_bUKwccdpyLDQim0WKLb?usp=sharing

edit: fixed link

 

[mattd]

Replace the subframe.

 

[GMFan]

I will take to the dealer I've had recall work for the front sub-frame and see if they are willing to work with me. I will request they send pictures to Mazda corporate for their review. I'll keep you all updated on what happens...

I spent yesterday applying POR15 to the rear areas of the car frame and underside body panels. I left the rear-subframe alone for now so the dealer can visually inspect. The POR15 dried to a black piano like hard finish. Really neat stuff. I will post pictures when I have a change of how it came out.

Thanks everyone for help/suggestions. Happy 4th of July!

 

[Danno]

I appraise cars at a dealership, and we just had a 2010 Mazda 6 come in for trade with 146,000 miles on it.
This thread had me worried so I had one of our mechanics inspect the rear sub-frame and shock towers for corrosion.
Surface rust but nothing like the pictures. The car can be certified.
We use rock salt up here for snow and ice on the roads.