Theory rear wheel well rust

[TerryW]

Okay so I'm aware that this is an incredibly common issue, and I'm sorry if this is repetitive, but I do believe I've figured out whats causing it.

While I was cutting out the wheel wells (not fun) i noticed that the outer metal seemed to be fairly intact (strange), which led me to believe that the rusting was occurring from the inside out (dafuq?). Further investigation led me to understand that this was in fact the case, as must of the rubberized coating (rhino-liner, more or less) that protects the outside of the wheel well was in perfect condition. When I removed the rear bumper I was introduced to a vent that uses air flow to pull air out of the trunk for ventilation (aha!). This was my first clue.

When I got under the car, I realized that there is little to no heat shielding above the mufflers, which as you know sit directly below the trunk at a fairly close proximity. Then it hit me.

The mufflers heat the trunk (and its contents) to a point at which any moisture in the trunk is vaporized, and for whatever reason, is not pulled out of the vent (likely due to the aging of the rubber flaps, which then become stiff). Thus, the buildup of moisture has to find somewhere in the trunk to settle, which means the highest, coolest point in the trunk. This would be the tops of the wheel wells, which are the farthest points from the heat source (mufflers). This process, over a long period of time, results in the notorious wheel well rust at the top of the struts.

This is my theory. Give me your thoughts.

T

 

[16MustangVet]

The rear quarter panel rust is mostly caused by water getting in around the gas filler neck and trapping the moisture in. If you look around at all the cars that have rear fender rust its mostly on the side with the gas door. Also same reason some cars have rusty gas doors when the other side is perfectly fine. The vents your talking about are way down in the back part after the rear wheels and that's only covered by the bumper. Even with the bumper on you can stick your arm up in there and open the vents like a shutter if the cars on a lift or high enough.

As for the high points like the strut towers that rust in the rear, over time the struts wear out the sealant around the pinch welds where more than one layer of metal is spot welded together and once water gets in there it turns to cancer fast. Spot welds are a nightmare unless they stay sealed from the elements.

Just my 2 cents.

 

[Fivefingerdeathpunch]

Maybe.


Also look up in the wheel well where the strut plate is spot welded to the car. You'll see that there is alway an overlap of metal where two pieces of the body join that is not sealed off, moisture and salt get in there and rust away the metal.

 

[TerryW]

So,

Update.

Whatever the cause of the problem, I fixed mine and have all four wheels rolling again. While attached the the car.

Someone said the best solution was a donor car extract and welding, which I had to do on the drivers side. I cut out way more than I needed to, brought it home and got it matched and fitted with a lot of measuring and trimming. I drilled approximately 20 holes and bolted it with varying sizes of carriage bolts and (tempered steel) machine screws. This was for both additional structural integrity as well as pulling the two sheets together at critical points to ensure a better weld. I coated the overlaps with extremely high tension construction adhesive, bolted everything in tight and welded where I could. I then sealed all the cracks and overlap gaps with watertight seal and sprayed the entire thing with a layer--or twelve--of rubber undercoat.

The passenger side was somewhat less damaged, so I took a 1/4" thick steel bar, cut it to length, bent it to shape, and used a hammer and pry bar to get it up above the strut plate but below the wheel well. I bolted both sides and ran a bolt through the strut mount plate and bolted it there too, again, just trying to pull it tight so the welds would take more solidly. I welded it where I could, and sealed it like I did the driver side.

Two months later, she's still rolling pretty with no noticeable creaks, groans, pops, etc. It's not permanent, but it's bought me some more time with the car I love.

-End