Mazda Rear Subframe Rot - Pics

[jpajya]

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!

GMFan, following up with you on rear sub-frame rust issue.
I see in your maintenance thread that you ended up replacing the rear sub-frame. I'm looking to do same with a 2011 Mazda 6. Once I get the second-hand subframe in hand, I'm going to attempt to DIY it.

Looking to see if you had any issues or recommendations for me to consider.

In addition to replacing rear subframe, I will have to replace the left side "stopper" (top half metal, bottom half rubber, refer to 28-111B in attached diagram) that sits inside the left rear coil spring, since the stopper completely detached from its top mount due to rust. Also looking to replace both left and right rear coil springs while I'm at it, since the car is at 117,000 miles. In addition to diagram, also attaching photo of left coil spring with separated stopper, and the inside top of the coil spring where stopper attaches.

 

[PimTac]

This will alert him to your question. @GMFan

 

[GMFan]

GMFan, following up with you on rear sub-frame rust issue.
I see in your maintenance thread that you ended up replacing the rear sub-frame. I'm looking to do same with a 2011 Mazda 6. Once I get the second-hand subframe in hand, I'm going to attempt to DIY it.

Looking to see if you had any issues or recommendations for me to consider.

In addition to replacing rear subframe, I will have to replace the left side "stopper" (top half metal, bottom half rubber, refer to 28-111B in attached diagram) that sits inside the left rear coil spring, since the stopper completely detached from its top mount due to rust. Also looking to replace both left and right rear coil springs while I'm at it, since the car is at 117,000 miles. In addition to diagram, also attaching photo of left coil spring with separated stopper, and the inside top of the coil spring where stopper attaches.

I commend you for taking that on as a DIY. I had a shop do the job. The only thing mechanic mentioned was that they re-used all the any hardware and fasteners that were on the old subframe as none came with the junkyard subframe. Im assuming they reused the existing 28-111B, because they never mentioned it. If I recall my stopper was yellow rubber and it definitely appeared like it was the old one (it was a bit beat up). Perhaps you can tell from the pictures after the job was done?

Go to post #48 in this thread.

Time to Dump or Repair?

Originally Posted by GMFan ... Hopefully I can find the part I need. Tempted to POR15 it all before it is installed. That wouldn't be a bad idea, then if there is access internally coat it with internal frame coating (might not be a bad idea to do the front too if possible) maybe even chassis...

bobistheoilguy.com

Looks like the old bump stops to me.

 

[jpajya]

I commend you for taking that on as a DIY. I had a shop do the job. The only thing mechanic mentioned was that they re-used all the any hardware and fasteners that were on the old subframe as none came with the junkyard subframe. Im assuming they reused the existing 28-111B, because they never mentioned it. If I recall my stopper was yellow rubber and it definitely appeared like it was the old one (it was a bit beat up). Perhaps you can tell from the pictures after the job was done?

Go to post #48 in this thread.

Time to Dump or Repair?

Originally Posted by GMFan ... Hopefully I can find the part I need. Tempted to POR15 it all before it is installed. That wouldn't be a bad idea, then if there is access internally coat it with internal frame coating (might not be a bad idea to do the front too if possible) maybe even chassis...

bobistheoilguy.com

Exactly the info I was looking for, especially regarding re-use of old hardware. Looked like they were able to reuse your upper and lower (rubber) coil spring mounts, so I'll look to do the same if they are suitable. Incredibly helpful details in your note and in your thread, as well as the photos. Your junkyard subframe looked in great condition in relation to our rusted ones. I've ordered a used subframe off of what looks to be a reputable source on e-Bay for $300 (includes shipping), and hoping it's half as good as your replacement. Not sure if it will include the left and right "stoppers," so I'll look to see if I can get one for the left side since that one is too damaged to re-use.
Will let you know how it goes. Many thanks.

 

[jpajya]

Well, the e-Bay subframe (LKQonline) arrived and was in terrific condition. Unfortunately, it was for the front subframe (first pic below). I initially decided to refuse the shipment (and LKQ was easy to deal with since the error was theirs), but I ultimately decided to keep the front subframe since it was in such good condition, and I had already been thinking about tackling that job down the road.

Decided to look locally for a replacement rear frame and ultimately found one using www.car-part.com. Was fortunate to find a rear subframe for $100 that came from a 2012 vehicle with 14,000 miles. When I went to the salvage yard to pick it up, they brought it out on a forklift and it turned out to be the entire rear suspension assembly. The guy offered to tear it down to the subframe if that was all I wanted, or, for the advertised $100, save them the tear down effort and let me take the whole thing. I just took the whole assembly since it would be a complete upgrade for my rear suspension that had 117,000 miles on it, and in some ways, may have been easier to remove/install. Replacement subframe is at picture 2.

One 4oz can of POR15 was more than enough to apply two coats to the subframe and some minor rusted parts on the trailing and suspension arms.

Using this 1A Auto video as a guideline, was able to remove the old subframe (picture 3). Much of the installation can be done without help, but definitely helpful to have an extra body to assist with getting the subframe and trailing arms aligned and in place (picture 4).
Taking the car to local shop tomorrow for alignment to complete the job.

Greatly appreciate @GMFan for the helpful info in this thread that he started.

For more details on my subframe replacement, I've also got a thread on mazda6club.com.

 

[jpajya]

Here is some additional insight regarding my experience with subframe deterioration for a 2011 Mazda 6 with 117,000 miles.

The worst deterioration was at the trail/rear mounting posts (immediately above the coil springs), with the driver side being the worst. The lead/forward mounting posts also showed deterioration, but less severe than the rear. First photo shows overall, second is the driver side trail mounting post, and third is pax side trail mounting post. Could probably have squeezed more miles out of it, but my son is primary driver, so preferred to just eliminate the problem.

As mentioned in my initial post on this thread, the bump stop housed within the coil spring on the driver's side had deteriorated to the point that it was no longer affixed to the subframe. The fourth picture shows where loose bump stop should have been mounted (with the coil spring removed).

 

[Cdn17Sport6MT]

@jpajya , on the second gen Mazda6 (as on the 3rd gen Mazda6) access to the top of the subframe for additional corrosion coating, as you did, seems only possible if the frame is dropped down. Is that your sense as well?

 

[jpajya]

@jpajya , on the second gen Mazda6 (as on the 3rd gen Mazda6) access to the top of the subframe for additional corrosion coating, as you did, seems only possible if the frame is dropped down. Is that your sense as well?

Well, removal is ideal, but I suppose it's possible to loosen the 18mm nuts on each of the four posts (leaving the nuts secured to the lowest threads so frame doesn't drop), and that might gain a bit more space to try to cover some of the top, but ability to do any prep work like wirebrushing or sanding would be limited. On the leading/front posts, there is also a support bracket on left and right post held in place by two 12mm nuts that would need to be removed.

Here's a couple photos to give some perspective. Picture 1 shows driver side leading/front post lowered, with the 12mm nuts removed from the black support bracket. Picture 2 shows passenger side rear support lowered, and you can see threads still remaining on the bottom of the stud to secure the 18mm nut. In Picture 3, you can see the gap above the passenger side coil spring is somewhat accessible, (as is the driver side, but I don't have a photo).

For any lowering of the subframe, you'd also have to account for the muffler below the subframe to avoid dislodging anything, but lowering while keeping the bolts on the stud should keep it high enough not to interfere.

 

[Cdn17Sport6MT]

Y

Well, removal is ideal, but I suppose it's possible to loosen the 18mm nuts on each of the four posts (leaving the nuts secured to the lowest threads so frame doesn't drop), and that might gain a bit more space to try to cover some of the top, but ability to do any prep work like wirebrushing or sanding would be limited. On the leading/front posts, there is also a support bracket on left and right post held in place by two 12mm nuts that would need to be removed.

Here's a couple photos to give some perspective. Picture 1 shows driver side leading/front post lowered, with the 12mm nuts removed from the black support bracket. Picture 2 shows passenger side rear support lowered, and you can see threads still remaining on the bottom of the stud to secure the 18mm nut. In Picture 3, you can see the gap above the passenger side coil spring is somewhat accessible, (as is the driver side, but I don't have a photo).

For any lowering of the subframe, you'd also have to account for the muffler below the subframe to avoid dislodging anything, but lowering while keeping the bolts on the stud should keep it high enough not to interfere.

That's helpful; thx!

Mine is a Mazda6 third gen. I'm not contending with any measureable amount of existing corrosion... but what I want to do is purely preventative. My sense is that there are also boxed-in, inaccessible areas that need a creeping, waxy, blown-in "cavity sealer", too. Do you agree?

 

[jpajya]

Yes, there are boxed in areas that would be a challenge. I'm not so familiar with the wax sealers, but there are holes and gaps throughout the subframe that could allow for insertion of a tube if spraying a rust preventer within those areas. The first photo in Post #46 gives some visibility of those holes and gaps.

 

[researcher]

Yes, there are boxed in areas that would be a challenge. I'm not so familiar with the wax sealers, but there are holes and gaps throughout the subframe that could allow for insertion of a tube if spraying a rust preventer within those areas. The first photo in Post #46 gives some visibility of those holes and gaps.

Almost like they thought of this.. check out Eastwood's internal anti-rust coating.. very cool and it comes with a spray hose..

Eastwood Internal Frame Coating Rust Prevention Aerosol

Destroys rust hiding inside the chassis, rocker panels and pillars so it won't rust through

www.eastwood.com

 

[CapitalTruck]

I swear, when you see rust that bad on a 12 year old car it makes you think something was just plain wrong in manufacturing, like there is some erroneous chemical reaction taking place that goes beyond the standard salt caused rust. A couple of Silverados I’ve seen are like this, like just exponentially worse than their comparable year/make/model/mileage/climate peers.

 

[NormanBuntz]

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.

I spent four years in Syracuse. Those winters just destroy steel. Be glad you didn't have a Fiat or an Alfa Romeo, but Mazda isn't the only one with frame corrosion recalls. Honda has one on Gen 1 Ridgelines. Gladly mine easily passed the inspection.