Not-So-Permanent Floor Pan Repair or Patch?

[williestargell]

1983 Chrysler L-Body - to no one's surprise my passenger side floor pan is covered in rust. After removing most of it, I saw a few holes that have eaten all the way through. There are two dime-sized holes, one in front and one in the rear; as well as 5 or 6 pea-sized or smaller little holes or small clusters.

As far as I can tell there is no replacement floor pan, and it is a huge PITA to make a new one and de/re/install it.

I'm looking for advice on a temporary Patch. Wondering if cutting sheet metal and epoxy/liquid nails-ing it over the holes might hold for a few years. The general plan is, since I've got the carpet and pads out, hit everything with rusty metal primer (after patching i'd assume) and a few coats of paint. Probably not going to have this vehicle more than another 5 years, so really just looking for a way to keep water out for a relatively short period of time.

Is there a preferred sealant of some sort? There's a lot of rust though it's down as far as I can get it without making more holes...

Thanks!

[going4speed]

Rust is deceptive. If you see rust triple what you see and that's likely the whole story. If you have a hole triple it's size and then you will be into solid metal. The thing about rust is that if metal is rusty it keeps rusting so covering it up will make the rust worse in a few years as the metal will continue to oxidize under your repair. It sounds like you have no access to a welder. At that point I believe your best bet is cut out as much of the rot that you can and treat the remaining rust with a rust treatment that will stop the progress of this sinister mess.
To patch I would say a temporary patch would be best achieved with a two part seam sealer and sheet metal of the same type to avoid any galvanic transfer. By that I mean carbon steel and dont use aluminum. Once applied and feathered out flat I would then cover with epoxy primer to keep it from absorbing water.

[4 l-bodies]

Is the rust on the inner floor pan or the underside (outer) floor? If it is inner then you have a leak somewhere that is letting moisture in. All that carpeting and jute backing just becomes saturated and the moisture has no way out until it rusts through the sheetmetal. You really should find the source of the leak, repair that and then repair the floor. If you have the carpeting and seats out of the vehicle you could cut the rust out, make some patch panels from sheetmetal and have someone tack them in. That shouldn't cost that much since you are doing all the prep work. Even lower cost option would be to pop rivet some new metal in place. Then seal them like going4speed suggests.
Many L-body guys have almost the entire floorpans ate away, yours seems like a pretty easy repair compared to what others have to deal with. The common places for L-bodies leaking is the cowl area, door weatherstriping, seam under front fender, floorpan to firewall seam, windshield, and yes rear taillights. I tracked one L-body leak that leaked into front passenger floorpan to right tail light leaking! Depending on how the vehicle is parked, it can easily leak all the way to the front footwell. If you choose not to find and repair the leak I would consider leaving a drain hole at the lowest part of the floorpan, so moisture can find a way out. POR-15 might also be a good option for you. google it if you don't know what it is. There are other brand names that are basically the same product. Metal Saver or something Saver is another brand.
Good luck,
Todd

[williestargell]

Thanks for the replies - I can't see any rust on either side from underneath the car. The leak I know of is driver's side door weatherstrip, which is why i park on a slight uphill. That side is OK though, there's a decent amount of smooth metal. May try to use the epoxy & rivets method. Wonder if I can find steel at the hardware store.

[Aries_Turbo]

Pop rivet metal in.

Buy rust bullet www.rustbullet.com. Make a patch. Drill two holes through it on either side of the patch and rivet in place.

Then drill around the perimeter of the patch and place a rivet in each hole by hand as you go just to make sure the holes all line up. When all the holes are drilled, drill out the first two rivets that were actually "popped" to hold the patch in place.

Then remove burrs on the metal and Clean with solvent.

Coat all layers with rust bullet and while it's wet, rivet the patch in place. It makes a huge mess but it works awesome.

I've had metal rust out around one of my patches like that.

Brian

[williestargell]

So i've got a rivet tool and some steel sheet metal. i just finished my second coat of rustoleum rusty metal primer. On a bit of a time crunch with this project, but trying to do the best I can with the tools I can get to. Going to cut patches larger than than the holes by a few inches, prime the patches, and use a marine-grade silicone sealer under the patch. These will then get rivet into place while the sealant is wet. I'll paint over everything with auto spray and hope this will get me a few more years out of the floors here. Rust bullet looks like a good product, just not sure I have the time for it right now. In a few (and every few) months I'll check under the carpet and under the pans again and assess if things are doing their job.

sound like a reasonable plan?

[Aries_Turbo]

id use seam sealer rather than silicone but if its what you got, then use it.

if you fix the leaks up top, then your fix will last longer.

Brian

[williestargell]

id use seam sealer rather than silicone but if its what you got, then use it.

if you fix the leaks up top, then your fix will last longer.

Brian

Is this seam sealer in the same vain as "Zinsser Watertite" or similar? What I've found is usually poly or poly/vinyl in a caulk tube... The Rusto paint is oil based or enamel

Also it's been raining for two days and there isn't anything wet on the inside. I'm thinking years of neglect before I got the thing

[Aries_Turbo]

I dunno. i get seam sealer in a can from eastwood automotive.

its really stinky stuff. full of solvents or something smelly.

works well though.

Brian

[going4speed]

Fusor 800ez is good stuff and cheap.

I have been using 2 parts epoxy seam sealer from 3m lately and I think i'm converted for life! That stuff sets up over night solid as a rock with zero smell left.