Rusty Battery Box advice needed
 

Hey guys.
The first thing I need to address on the 911 is a bit of rusty residue in my battery box. I poked it with a pick and for the most part it is still solid. The PO of the car was using a plastic tray under the battery and this would still work ok but I want to address this area now rather than taking a chance on it getting worse later.
The box is very dry, it doesn't appear as if acid has been on the metal for a long while, and I would like to clean it as best I can, maybe prime it, and in the one or two small places where there appears to be a hole fill that some how.
I plan on continuing to use the plastic tray as well as a battery tie-down somehow.
I'm attaching a photo, so if y'all would look it over and give me your suggestions I'd appreciate it. Top left and bottom right are worst areas.
Thanks!http://forums.pelicanparts.com/uploa...1249176452.jpg

I sprayed some rust killer paint from Rustoleum.

as long as it's still solid, I'd clean everything spic-n-span and then POR15 the heck out of it.

Wire wheel to bare metal. Prep/prime with POR-15, then paint to your desire (or leave the POR-15 finish...no one but you will ever see it). Your battery tie-down consists of the metal lip toward the back and another clamp in the bolt-hole toward the front.

after you do the above switch to a gel type battery unless you want to do this once a year

The current battery is a NAPA special that the PO installed. The thing has fixtures for two vent tubes on it and I can see where One was attached as part of it is still on the battery. But none run out of the bottom of the fender or wherever it should go to drain.

The overflow most likely came from the battery tender being on too long (my somewhat un-educated guess) or possibly heat and it overflowed into the plastic tray below. Just about 1/2 inch or so but too much acid for me!

I'm assuming POR-15 can be had at any good automotive paint supplier?

Thanks so far, guys.

Not sure I've ever seen it in a store...always purchased on-line: www.por15.com

Thanks WilsonTC ... and others!

Most of my local auto paint stores sell POR, and for often times less than the shipping costs from POR.

+1 on the recommendation for POR-15. If you're going to fill the holes, though, you might check with POR-15 to be sure that the paint will properly bond to whatever you're going to use to fill the holes.

Good luck!

I thought about using the round wire brushes from my rifle cleaning kit to try to clean out the holes where it looks like the bolts for the safety clamps go.... I want them to be rust free as well as I want to use them for the safety clamps.

I would use a brass brush (size of a toothbrush) and scrub the area by hand using a solution of Baking Soda and Hydrogen Peroxide. The solution will neutralize the rust. Use plenty of water-soaked rags to clean the area thoroughly. Then apply the POR-15. If you choose, prime and paint the area afterward.

There are a couple of guys here that have the link to some places with great touch-up colors.

Anyone have photos of how non-gel battery 'should' be properly vented? None of the holes in the area of the battery tray seem to pass all the way through the sheetmetal to the exterior. I currently have medical tubing extending the battery vent tube - to nowhere, just lying loose in the trunk .

I had thought of using baking soda to neutralize the acid residue but have bought the starter kit of the POR-15 which has two solutions in it and enough paint to more than do the bat. box. After buying the kit I read the instructions, duh, and it mentions washing the soloutions throughly... I may not been too keen on putting that much water in my "trunk." I will have to eyeball it when my chemicals get here.

Fine question as I have wondered this myself!!!

That is why I suggested using water-soaked rags for cleanup. This ain't no Ford, where you can just grab a hose and go crazy. It'll take a little finesse.

As far as the gel batteries go, here's my opinion...please note that this is ONLY an opinion. The subject of gel batteries (Odyssey) versus good ol' Interstate batteries will stir up the same amount of venom as the "Bra vs. No Bra" debate. :rolleyes:

I used Odyssey gel batteries for years in my custom Harley applications. They are very expensive and can be a pain in the a$$. They tend to crap out quickly, if frequently allowed to drain...leading to the subsequent recharge. They just can't take that kind of abuse very long. Yes, they are lighter. Yes, they are cleaner. But they are kind of "maintenance-intensive", unless your electrical system is completely (and I mean COMPLETELY) trouble-free.

And although I'm no expert with Porsches, I can safely say that very few of these cars fall under that catagory.

Just my .02 cents. ;)

I appreciate your "two cents."

I would suggest cutting a few "inspection" holes and looking in the void between the suspension pan and fuel tank support.

Quite often, if battery acid spills are not well-cleaned, residual acid stays in this void and causes a lot more corrosion than may be apparent. I had similar, perhaps even less, visible rust on my '85, but when I dug deeper I found it was much more than I expected. And this was a car from a good climate with a spotless body otherwise. You can see my story here:

http://forums.rennlist.com/rennforums/911-forum/499091-battery-area-surprise.html

However, you may be more fortunate (and I hope you are), but it is better to open in up a bit and really know what you are up against first. Best case you just weld the access holes back up - you have to do paint work there anyway.

Another clue may be visible when you look underneath the car. The bottom of the suspension pan under the fuel tank support has three, soft rubber plugs covering drain holes. If you see an orange-ish hue around these plugs, that is a definite sign of corrosion going on inside.

Good luck!

Got to the battery box for a little while this morning and the job that I was sort of dreading isn't going to be so bad afterall. The photo actually makes it look worse than it is. The rusty color is so very light that a few passes with the little wire brush had it gone. I plan to take my drill with wire brush attached to finish removing all of the original coating as I am leary of some corrosion hiding under there. All in all it is going to be a Very light job with Very minimal metal damage....except for the top left in the photo where the open place is in the metal... I was wondering if I should JB weld that gap together or just be sure to get the POR-15 on there good?
Any opinions?

That's good advise.... I just saw this post after I posted the one above... I'll check this out!
Thanks!
--J

The vent tube is for the hydrogen gas escaping from the cells as they charge, not for excess acid. Seems you could safely connect it to the vapor system?

Quote.... "The vent tube is for the hydrogen gas escaping from the cells as they charge, not for excess acid. Seems you could safely connect it to the vapor system?"

Interesting...
When I bought the car the battery was resting in a plastic tray. Inside the tray was a clear liquid (about 1/2-inch or less) that I assumed was acid. Not being the dumbest thing walking I didn't taste it to be sure it wasn't water! I just assumed it was acid.
The battery is only a few months old, so it makes me wonder if acid had indeed ran into the plastic tray via the vent like I suspected.

After getting into the box I have found that most of what you see in the photo is discoloration of the rubberized coating on the bottom of the box. There were only a few places where this coating was broken and the metal exposed.

Last night I posted on the paint and body forum about my intention of stripping the entire box to bare metal and doing the POR-15 thing, but now I'm wondering if I should consider not stripping off all that coating as most of it is still afixed strongly to the box. My thought is that since there is a small opening of the metal (top left corner in photo) maybe I shouldn't seal it up and POR-15 the whole thing before maybe letting a qualified body man have a look at the underside of the box to see if there's hidden corrosion. On shining a light, the hole in the box not is visible through to the underside of the car, but what if, right?

I hate not doing the entire job I've started but in light of the work involved to do it and possibly only having to cut away some of the metal to check underneath the box, how would you guys proceed?

Any opinons?

Thanks!

There will likely be some (hopefully small) areas where the PVC coating has some corrosion happening. These areas must be cleaned to bare metal. The trouble is identifying any such areas prior to getting busy with a wire wheel or such. Some areas will be obvious, some less so. Where to draw the line is a hard choice. Each step you take gets you that much closer to just ripping the whole thing apart and re-doing it! Looking at the picture, things are quite advanced on one spot along the lap seam where the fuel tank support meets the longitudinal. There is a good chance that acid worked its way through that seam. That is very similar to how mind looked. But again, don’t take that to mean that it is as bad as mine was – there are likely many factors at play.

Based on my experience as well as feedback from others:

1) The chance of there being corrosion in the void between the suspension pan and fuel tank support is reasonably likely. The tray is not perfectly sealed and usually a little acid gets in there when there has been a leak, and it doesn’t take much… This is something that lurks on a lot more SC’s and Carrera’s than maybe we want to believe. I had thought I had very little corrosion and that it was mostly just stains (that wiped off easy enough). Boy, was I wrong…

2) Having said that, it quite possibly is not MUCH corrosion in your case, so the real question is how perfectly do you want to fix it? Mine was not rusted through, but the sheet metal was noticeably thin in some areas. You may want to investigate this. Underneath the car, push VERY firmly with your thumb EVERYWHERE on that portion of the suspension pan between (and around) the forward lower control arm mounts and along the area in front of the tank. I was able to visibly see the sheet metal deflect in a few areas where it had become quite thin. If your car passes this test, then it would mean that if there is any corrosion in that void, it has likely not gone too far. In this case you may elect a fairly non-invasive approach (described below).

3) If it fails this test (or worse, if you find areas of rust-through) then I think the only real option is to replace the sheet metal.

In summary, the fundamental problem is that the most important damage is the least accessible. Soaking everything you can in POR 15 or such may not get to the crux of it.

Looking from the underside up into the void is not what you want, you need to look from the top-down. All the corrosion (if any) will be on the bottom surfaces of the void.

“Non-invasive” approach (where corrosion damage is minimal):

1) Remove fuel tank (you will want to make sure that acid did not soak into the fuel tank seal and start doing its nasty work there). Not difficult to fix if it did. However, you will need a new fuel tank seal to re-install, no matter what.

2) Strip all the PVC from the battery box area near any corrosion. You will figure out what you need to remove as you go. If you use a brass wire wheel on a drill, with moderate pressure, you should be able to remove the PVC and leave the E-coat still on the steel (well, my ’85 had E-coat – other model years may vary on that…)

3) Grind/sand away all corrosion. The brass wire wheel alone may not fully eradicate the corrosion (especially if there is any pitting).

4) Prime and paint. I know people are big on POR-15, but I would prefer a series of activated auto-refinish products from a quality supplier (BASF, PPG, DuPont etc.): Etch primer, stoneguard/pvc of some type, HS primer and then top coats (base/clear or single stage) would allow you to get a very OEM look – however, it would be more expensive and complicated, so it is up to you.

5) Using an undercoating wand, liberally spray the inside of the suspension pan/fuel tank support void with a wax-based corrosion protector such as FluidFilm. If you don’t have an undercoating gun (not too expensive) FluidFilm is available as an aerosol and if you use one of those plastic “needle” tips and spray liberally in all directions, you should be able to do a good job (and undercoating wand is just more “definite”). This should arrest and rust that is happening and prevent things from getting worse. You will spray through the three vent holes on the underside.

It all comes down to how much of a perfectionist you are, how much damage there actually is, and how long you are willing to lay your car up for. If you ultimately do go the suspension pan replacement route, it is a do-able job, but it will take a while!

P.S., I surfed over to the paint and body forum, I guess my stories got you worried… Sorry about that, I was just trying to relate some of what I learned. I always prefer to know what the real deal is. However, I do apologize if I have caused you undue worry.

I think if you do the thumb test I described above, and just generally knock around on the sheet metal under the car, it will hopefully assuage your worst fears. My fingers are crossed for you.

Thank you so much for the great reply. Worried a bit, yes, because "she" is my baby now and I want her to be around a very long time... and, I don't want any possible corrosion to worsen to the point where we have to do major surgery!
Thanks again!