Google search “924 944 battery tray rust” and you’ll be met with a nasty sight. I don’t think there’s a single car that hasn’t had this issue, and mine does.

The problem is that at some point, I believe battery acid and sitting water causes corrosion issues that aren’t noticeable right away because the galvanized bodies. But eventually the rust will get so bad that:

  • Water will begin to leak in the passenger footwell
  • Depending on the year, water will leak onto the 944's engine computer
  • And if you’re super unlucky, the water and battery acid will leak onto your floor and cause that to rust....It ain’t pretty.

On my 944, it was a non-issue and had probably been dealt with prior to me. On my 931, you can see the inevitable pitting and corrosion that I had to deal with. Not only that, but a dime-sized hole had rotted it’s way through in the location designated by the arrow above and water was pooling into the thankfully painted passenger footwell. Ironically, this picture is of another Michigan 1980 931 that had it worse than me.

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On the left is how it looked initially, the right after taking a dremel to the worst areas. You can also see the hole in the lower right of both pics.

Now for my fix, rust is a cancer and the only definitive fix for it is to remove it all. Unfortunately that would require cutting and welding and that’s just not possible for me right now. A fiberglass patch could work, but I don’t have the time for that either. I remembered seeing hilarity involving expanding foam. So after cleaning up the rust hole as best I could, I stuck the nozzle of a Loctite brand foam can and filled it up. I then used a rust encapsulator on the exposed metal and rust, followed by a lot of primer, all after letting the foam set and cure for an hour.

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It’s supposed to rain tomorrow, so lets see if my theory works, and if so, for how long.