Fix'in a Rusty Floor

[steeleygreg]

Folks, need some advice and the correct course of action to be taken with our elusive enemy of Rust Repair. Rusted metal was cut and new welded into the existing floor. Repairs were made to the driver side passenger floor.
The sources which caused this rust were in the front of the car and have since been sealed up and the floor remains dry even in heavy rain!
I looking for some words of wisdom in finishing this job ! On the car interior, I plan to use a seam sealer followed by a rust encapsulator, followed by paint. For the underside exterior of the car, the plan was to seam seal, rust encapsulate the area and then use bed-liner paint to seal up the remainder and extending this out to bond with the existing factory undercoat . My understanding is this bed-liner paint is flexible so as it will give with the car.
Is my thinking here correct, or is there another approach ?

[bricktron]

that doesn't sound like any worse of a plan than what i had done on my car. congrats on making the fix.

[Stretch]

My problem with the original rubberised coating on the W123 is that it traps water inside it; and the water propagates further along the panel rusting more and more...

...for that reason I favour something like POR15 and then their chassis top coat. It is pretty tough stuff and if it does get damaged I'd expect the rust to be a small localised patch (equal in size to the damage)

[steeleygreg]

Thanks bricktron for the complement. Stretch I agree with you. Got to top coat POR 15 for its not UV stabilized.
Thanks, this was along the lines of what I had planeed but wanted to talk to the collect intelligence for any further information.

Greg

[Stretch]

The only down side to paint is that it isn't at all in the fit and forget camp - you do need to check underneath once in a while to see how it is doing the job (or not). But anyway to encourage people to consider the condition of their cars before they step in them and zoom off at 200mph is a good thing in my book!

[steeleygreg]

I agree with that, but how many check their cars condition constantly! I was thinking about this the other day, in relation to these spots that where welded with new metal. Since the back seat floor area is the low spot in the interior compartment and it appears from reading and experiece that water gathers in these areas, wouldn't it be a good idea to put a moisture sensor on the floor with some kind of alarm. Probably would not be expensive and my alter drivers of potential rust problems way before they degrade any metal ? Just a thought...

Greg

[Smoker]

I'm so paranoid about the tin worm that I *do* pull back carpet, take out trunk panels and go under the car to check out the common rust areas, especially those I've repaired before.

Remember the old electrolysis anti-rust systems they sold back in the day? Sure wish they hadn't been snake oil.

[Graham]

When my rust repairs were recently done, I decided not to put down any of that stickyback soundproofing (like Dynomat). Actually, I did put some down, but only on vertical surfaces like front of back seat and firewall. I also put some on the high spots on the floor. But none on flat part of floor. I stil have the original carpets and mats and they have heavy underpadding which seems to be sufficient.

On the underside of the car, we used DOM-16 which is similar to POR-15 but does have UV resistance (available at NAPA in Canada, not sure about elsewhere). I sprayed asphalt rocker guard over the DOM/POR repairs, but only on underside of car. (partly cosmetic, just to make everything one colour (black).

On floor pans I just left the paint with no overcoating. Just have to pull carpets to inspect it. Did same on two other cars and the paint still looks like new.

Biggest concern, were the repairs to the door sills. We painted them same as floor with DOM-16 on cabin side, but on inside of rockers, there is bare metal. I had some ideas on how to paint in there, but problem is that there is wax everywhere from both original rustproofing and subsequent treatment that we tend to do a lot of in Canada, so painting would not work. What I have done, is buy spray cans of Fluid Film and spray up through the rocker plug holes. I will later also do the conventional Canadian rust treatment (Krown or Rus-Check). It needs to be done on a regular basis.

[steeleygreg]

Graham, its interesting how Canadian's handle rust issues. The product you mentioned called Fluid Film I've used before in marine environments. Great stuff.

[Stretch]

I'm surprised that the products in Canada are so different from the products here in Northern Europe. I'd never heard of Krown or Rus-Check before joining this forum and it seems as though not many people have heard of Dinitrol (which is considered to be THE stuff here)

[Graham]

Originally Posted by Stretch

I'm surprised that the products in Canada are so different from the products here in Northern Europe. I'd never heard of Krown or Rus-Check before joining this forum and it seems as though not many people have heard of Dinitrol (which is considered to be THE stuff here)

I see Dinitrol has an agent in the USA, but it doesn't look like they have made any inroads into the North American markets. Looking at their product range, it seems they are well ahead of what we have so far as product range is concerned,

At least in Canada, we have automotive rust treatment shops everywhere. In our town of 130,000 there must be a dozen or more places that do rust spraying. Rust Check and Krown are the main ones, but many others spray other similar products. I had Krown just steam and high pressure clean the underside of my 300D the other day (they did it for $45!). While I was there, they had military vehicles lining up to be undersprayed. Must be a good business. Costs us about $120 per treatment.

We visit the USA quite often and am always surprised that even in the Northern states, there seems to be few rust treatment shops. Places like NAPA do sell the products, but it doesn't seem like an established business as it is in Canada and it seems in UK.

[funola]

Floor pans only rust from the inside if it gets wet. Have you found where the water is getting in on yours? My 83 (sold) had persistent water on passenger floor when it rains. Most of that water came in from under the battery tray, where the sheet metal (about 3" diameter area) rusted through.

My pristine 85 with very little rust has slight surface rust developing under the battery tray. I am cleaning that up now including the battery tray.

[Graham]

Originally Posted by funola

Floor pans only rust from the inside if it gets wet. Have you found where the water is getting in on yours? My 83 (sold) had persistent water on passenger floor when it rains. Most of that water came in from under the battery tray, where the sheet metal (about 3" diameter area) rusted through.

Amongst other areas , I had leaks through both side hinge pockets. Developed holes on both sides of foot wells, high up above handbrake on driver side and egr computer on passenger side (85 model). An area that should be inspected as well as hinge pockets them selves. Luckily I painted firewall with POR-15 early on in battery tray area and 15 years later it is still good - just gave it and tray a fresh coat!

My driver side floor pan rusted from bottom up. The frame rails on underside are hollow and have holes on the underside. My worst floorpan rust was directly above one of those frame rail holes. No doubt salt and water get up in there. As Stretch said, salt and water also get under undercoating and start rust especially where there are fasteners or other means of ingress.

It's hard to see how water gets to the metal on floorpans considering there is (was?) a thick layer of soundproofing stuck to it (especially in front). But I know it does, at least in those cable troughs on the rear floor pans.

[Stretch]

That sound proofing stuff is like a big sponge - despite its bitumen like ingredients - must be some sort of capillary action going on.

The weirdest thing about the whole W123 floor pan design is that they put in all of those expensive and difficult to identify rubber / plastic bungs and then covered over the top of most of them with the sound proofing and covered the underside with that rubber junk. You could never use them with out some serious "modification" to the sound proofing or the undercoating.

[steeleygreg]

Funola, I had the same problem with my 83 240D, which I still have the car and will not part with. Love that car. Rust occurred in the same area and the PO never cleaned the hood-hinge area nor under the battery tray. The combination of these two issue caused the rusted hole, at least that my opinion. Solution was to take some sheet metal and bend into the form of the corner. Use some 3M 101 Sealer and pop-rivit patch in place. Welding in that area would risk damaging other components on the other side of the firewall.

WOW, reading about the different anti-rust products from Graham and Stretch used in different parts of the world is kind of mind-blowing. What I mean by that is, in the area where I live no body shop wants to or will deal with rust. They're only interested in replacing panels and insurance claims. Custom shops will do this, but it's pricey and not the standard. Guess that's American capitalism....... Might be a market for these anti-rust products in the US, but it just hasn't happened yet, at least where I am.

This thread was written for my new acquisition of an 85 300SD. The former owner was gracious enough to fix problems with the rust holes in the floor with welding in new metal prior to me driving it home to Maryland. We have salt used on our roads, but nothing like what's used where this car came from.

I told the PO that I'd dress the panel joints to protect them and thus this is the purpose again of this thread. Both the 123 & the 126 floor pans suffer from the same problem with water in my opinion. The passenger floor is lower than the front and this is why the water seems to gather in this location. At least that's been my experience.

As for the water leaks in both cars. Yes they have both been solved. In the 123 it was sealing and pop-riviting a 3 inch metal patch into the firewall. On the 126, it was a little more extensive and involved removing the plastic cowling in front of the windshield where the wiper motor is and sealing holes which led into the passenger compartment, on both sides of the car. Now both of these cars will have to be monitored every 6 months for rust problems, but that should not be a big thing.

I had no idea there where so many different products out there.
Got to see if I can get my hands on some of them to test.