Tom M'Guinn

Turns out I have a rust hole in my battery tray, and unfortunately it's in a bad spot. See pictures below. The interior picture is up above the big clip that holds the back of the glove box. When I poked at the rust spot with that green piece of wire, it went right through. The rust/hole is under the elevated battery mount plate in the battery tray. See blue arrow pointing to where the wire came out in the tray.

The battery box "looks" fine, and car has been garaged its whole life, so I was convinced it was fine. You never think it's going to happen to you.

Anyone ever remove the battery mounting plate/bar in the battery box to get to rust? Is it just tacked in, or will I have to hack it apart to get it out?

Are there any aftermarket battery boxes for this car (86 951)?

Options? Suggestions? Looking for a solid/forever fix...

plumbum

Curious did you have a battery cover on your battery?

Tom M'Guinn

So I'm finding lots of rubbery silicon under the paint, including under that battery clamp stand. Me thinks the original owner had some battery tray issues he forgot to mention... or is rubbery goo factory? This isn't just seam sealer around the corners -- for example, when I picked under the clamp stud I got big clumps of silicon/rubbery goo...

Calling all Larts... I can probably patch this, but would like to get my hands on a spare battery tray to see what it will take to get that clamp stand off so I can repair under it....

Tom M'Guinn

No, did not. I'm starting to think the car's been this way since I bought it in the 90's. I just never drive in the rain, so the one day I did I discovered this. The car has been garaged since new, but obviously had some rust-inducing early days...

Taymar

Mine has a big blob of sealer on the side where you found the hole. I don't know if it's factory, but on my car, that end of the bar looks like the two sides of the bar in your photo.

Edit: after a quick google images search for 944 battery tray, I didn't see any other images with as much sealer as mine has.

NoRush993/951

Usually the battery cover is missing, the car gets washed and the water drains right onto the battery. Does the acid leach out the top of the battery and get carried to the tray bottom with the car wash water and then start eating away the steel? That's what I thought happened. I caught mine early and sprayed some rust neutralizer on it. Seemed to stabilize the situation. Otherwise I was told the only solution is to cut out the bad part and weld in a new piece. There are electronics under the dash of the 951 that would be ruined if not rectified.

plumbum

Covers are under $20 from the dealer..first thing I bought for my s2 after finding a lot of rust on my 951

KevinGross

Rubbery goo could be the seam sealer used by Porsche around weld seams. It might also be an easy way for you to plug the hole you've got under the tray, as along as the rot is not structural or extensive. See Wurth's Brushable Seam Sealer.

Kevin
Catellus Engineering

Tom M'Guinn

There appears to be a heavy layer of seam sealer on the metal under the paint (like maybe 3mm thick or more). On top of that, in certain places, there is rubbery silicon or GOOP like stuff. I think it was some body shop's effort to seal it all up after the first time it had a rust hole.

Thanks for the Wurth suggestion -- someone else had also mentioned it. Looks like Pelican sell it too, so I'll probably plan to use that along with some kind of rust inhibitor on the metal.

Tom M'Guinn

Fast forward a few years and I finally decided to fix the battery box (for good hopefully). After peeling off the silicon someone smeared all over the pan floor (then painted red) and getting down to metal, I discovered two other rust repairs that had been done. Both were done ok, so I'm leaving them alone, but whoever did those repairs missed the rust lurking under the battery tray bracket. You can't see it from above, but it's clear as day if you pull the glove box and look under the dash. It was in a terrible spot too, with brackets spot welded above and below the rust hole...

Tom M'Guinn

Fixing this isn't for the weak of heart. I had to use a spot weld removing drill bit to get the battery tray bracket off the body, and do the same to get the glove box bracket off the bottom side. Once those pieces were off, the extent of the rust was pretty surprising.

Tom M'Guinn

Had to swallow hard to take a cut off wheel to the car, but didn't have much choice. 16 gauge steel seems to be virtually the same thickness as the body in that spot, so I made a patch using the Edd China paper trace method, with help from my trusty 3-1 brake-press (which is worth it's weight in gold for a project like this). I mulled trying to do fancy tig welds for the patch, but opted for a more tried and true MIG approach. It's just tacked in here, but I eventually MIG welded the whole thing to make it water tight without sealers (though I plan to use plenty of Wurth seam sealer anyway).

Tom M'Guinn

In the process of re-fitting the battery tray, I noticed my tray didn't have the little tab on the end like the newer cars have. Porsche seems to have added the tab in 87 or thereabouts. Without it, the battery clamp would dig into the body, so I added a tab to mine, as one of the more unique "while you're in there jobs" I've done...

Tom M'Guinn

The glove box bracket had some rust, so had to replace some of its mounting surface, then plug welded it from above. The primer is Copperweld -- a weld-thru primer. Did I mention this isn't a project for the weak of heart? I'll post the final results once I get the battery tray back on and do the seam sealer and paint... Hopefully, it will last forever now...

951and944S

Looks good.

Only think I may have done differently is, on your new patch piece, you could have had tacked strips that would have set the new piece precisely at level with the old metal and also allowed you to just tack through 5/16 holes drilled around the perimeter of your existing metal but it's really just a preference.

Either method....you don't really have to worry about welding your gap completely closed with a mig bead but still, it's just a preference that you'll decide for you own fix.

Personally, after using the spot weld method I described above....., I'd just grind everything clean (no weld through primer), prime with 2K epoxy. This way....when you grind your welds.....the strength is still present because you can grind flush with your old metal since the weld is below the surface to the strips you would have attached previously. Within the 24 hour window of wet on wet workability, I'd lay regular epoxy and cloth (not fiberglass cloth and polyester resin) as the epoxy primer and epoxy resin will be of the same molecular structure and will bond better that epoxy on polyester (google molecular chain of both products). You can then sand and swipe a thin coat of body filler for perfect finish. Body filler is polyester but it depends on a mechanical bond of a scratched surface not molecular bond. Brush seam sealer (Transtar makes a good one that is inexpensive and available through O’Reilly). Seal with a 2K Urethane sealer or just use the epoxy again mixed as a sealer so you don't have to buy so many products.

Paint to finish.

One of your problems here is going to be where to stop painting.

On a fender or door.....the panel is the ending boundary.

Here you are either painting red the entire battery/blower/fuse box panel or you will have to stop painting somewhere with an attempt to make it look seamless.

Hopefully it's still single stage there and the person who "fixed this" before didn't do base/clear.

I'll pop back in here to check on you.

T