Battery Tray Repair Attempt 

"K-Roll-PorscheTamer" (k-roll390) 05/14/2018 at 10:20 • Filed to: 931Lyfe, Project Car, rustventures

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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.

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.

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

someassemblyrequired > K-Roll-PorscheTamer 05/14/2018 at 10:30

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A couple of tips from when I had to do this on another car - first just make a baking soda/water solution and put it on to the affected area. Neutralizes the battery acid before you start trying to paint/patch.

If it’s a continuing issue, swapping for a Miata battery (the glass mat one) is not much more expensive than a conventional battery and they don’t leak.

Urambo Tauro > K-Roll-PorscheTamer 05/14/2018 at 10:32

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Wait, so the battery “tray” on these is part of the body? It’s not just a bolt-in tray that can be replaced?

K-Roll-PorscheTamer > Urambo Tauro 05/14/2018 at 10:33

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Yep! The only bolt in tray is the one you make yourself on these cars.

Urambo Tauro > K-Roll-PorscheTamer 05/14/2018 at 10:38

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Ah, bummer.

Pickup_man > K-Roll-PorscheTamer 05/14/2018 at 12:00

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While certainly not good, that doesn’t look too terrible. My 924 had the same problem and someone before me fiber glassed the battery tray, rather poorly. Not knowing this was a common problem when I bought it I didn’t look too hard at that area until I started noticing my passenger carpet being very wet. Further inspection led to this.

Can’t find any pictures of my fix, but that’s probably for the best. I cut up a somewhat decent looking battery tray, and after my crappy welder nearly lit the car on fire (multiple times) I sealed it up with a bunch of metal epoxy, silicone, and rustoleum paint. For the floor I wire wheeled off as much rust as I could, slapped a very heavy coat of rustoleum on it, then plopped down a semi formed piece of metal, siliconed the crap out of it, then coated it with several more heavy coats of paint. I am not proud of this fix, but it was a $1200 car, and that might still be overvaluing it. When I sold it I did mention the rust and the fix, because I’d hate for the next guy to be as pissed as I was when I found all of this, and before someone asks, the frame structure was still very solid, and I did my best to clean it and protect it before I covered it back up.

K-Roll-PorscheTamer > Pickup_man 05/14/2018 at 12:23

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Yikes! I remember that car, what year was it? Because the earliest cars weren’t galvanized and later went to only the lower half, and then the entire body in 1980, so mine should be safer. Didn’t know you’d sold yours, I was wondering when the next update would come around.

I still gotta paint it when I get home, but the primer should at least protect it until then, or maybe indefinitely until I finish other stuff.

Pickup_man > K-Roll-PorscheTamer 05/14/2018 at 12:45

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It was a ‘79, and I’m assuming it lived most of it’s life in the mid west. It was also a pretty high mileage car at somewhere north of 180k. I’m pretty sure it was also rear ended or backed into something at some point in its life as the rear bumper shock cylinder things were fully compressed. It was in decent shape all things considered, but I think that car likely lived a pretty hard life. That’s not mentioning all of the questionable repairs, upgrades, installations, and paint job that I found.

I’m kind of an introvert so I don’t post super often, must have forgotten to share the sale. I sold it last year near the start of summer to help fund a new bike. I really miss that car, but I really love my new bike.