Floorboard starting to peforate on my 85 300D

[Carrameow]

I was a little surprised these past few days when taking my engine and transmission out. After wrestling with my pilot shaft I kicked back on my Creeper and did a little daydreaming. I might of had a nap too. Anyway I looked up briefly to see a seam of light in my Pass side rear floorboard.
I wasnt that surprised. I think the W123's usually start the rot here. Nevertheless, the rest of the car was good, I gave it a good check.
My question is, whats the best solution to this?
Should I take my rug and my seats out and just weld a sheet of Galvanized steel across the top?
My car is still in good shape. Gas is getting expensive, its going to be ???$2.60 a gallon for 89 this summer?? I would like to keep this car running and looking handsome for a few more years. I dont want any duct tape ugly fixes.
Whats the best way to fix this?

[leathermang]

Go to the POR15 website and check out their products for floor repair...

[whunter]

Originally Posted by Carrameow

I looked up briefly to see a seam of light in my Pass side rear floorboard.
I wasn't that surprised. I think the W123's usually start the rot here. Nevertheless, the rest of the car was good, I gave it a good check.
My question is, whats the best solution to this?
Should I take my rug and my seats out and just weld a sheet of Galvanized steel across the top?
Whats the best way to fix this?

Never weld on top of a floor, weld new metal under it, this works with the stress of water and road trash hitting good metal, + you can pour rust inhibitor in between the layers/edges (with gravity help) from the top.

Look at post #175. - #181.
Who has the most rust and still drives
I am posting more pictures of this car tonight.

[leathermang]

Welding Galvanized anything makes poison gas...
and to get a good weld you have to burn the metal to get the Galvanization off... thus taking away the properties which you were probably choosing the Galvanized metal for... Catch 22....
Use some good old steel and really consider using the proper rivets and corrosion resistance like the Por15 instead of trying to weld in a floor... MUCH STRONGER.... and longer lasting....

[whunter]

Please look at post #186. - #190.
Who has the most rust and still drives

[leathermang]

Did I mention that I am on a slow dialup ? Or that you need to use the flash or more ambient light when making pictures... way too dark on most of them to see anything through my phone cord....

[rg2098]

Originally Posted by leathermang

Did I mention that I am on a slow dialup ? Or that you need to use the flash or more ambient light when making pictures... way too dark on most of them to see anything through my phone cord....

Check your monitor brightness. They look fine on my machine.

[leathermang]

I can see everyone else's pictures just fine... those last couple of rows are 90 percent black... why would I need to adjust my monitor ( if I knew how ) specially to view these pictures ? Are they dark to anyone else ? Did you have to adjust your monitor after you looked at the pictures or did they just show up perfectly viewable ?

[Carrameow]

I'm 45 now. i know some stuff..but I doubt I will know as much as you ten years from now...

[Carrameow]

I went their, but i didnt find anything specific. Which product do you recommend...

[leathermang]

I have about a twenty page information packet from them... they have things like " Patch" and steel meshed fiberglass... stuff they specifically recommend for fixing floors...
Will check that again and see if they have it hidden on their site...

OK, this for instance...

http://www.por15.com/product.asp?productid=81

I just got a gallon of Por15 and am cleaning a mower deck.... should apply it tomorrow.... after sandblasting and metal prep...

[Carrameow]

The rust gap is near the passenger seat seatbelt bolt so I guess in all conscience and considering the fact the better half sits here, I better do do my research. Should I weld it instead? Also since I'm not the worlds greatest welder upside down (welding from the bottom) I guess I may have to take it to a pro ($$^&(! hurts my pride)...

[leathermang]

All that means in terms of sheet metal is that you need to be sure and spread out your base properly...
I do not recommend welding inside a car... and for sure not from below.... lots of other ( and usually stronger ) solutions.. even if you are willing to pay a professional welder to set your car on fire.

Hint:
Aircraft welds are able to be x-rayed for quality when done and in future tuneups... at regular intervals ...

The rest of the plane is RIVETED TOGETHER.... because that is stronger, cheaper and lasts longer.

[whunter]

Originally Posted by Carrameow

The rust gap is near the passenger seat seatbelt bolt so I guess in all conscience and considering the fact the better half sits here, I better do do my research. Should I weld it instead? Also since I'm not the worlds greatest welder upside down (welding from the bottom) I guess I may have to take it to a pro ($$^&(! hurts my pride)...

Inspect all areas that I welded on your car.
Look for bubbles or soft spots in the rubber undercoat.
Use a small rubber mallet inside and your fingers under the car, try good areas first, to get the feel for bad metal.

I prefer weld repairs, cut out the rotten metal and weld in solid steel.

I test my welds with a five pound sledge hammer, if it knocks another rust hole loose, it needed fixing.

The rubber undercoating hides serious rust like a blanket, even good mechanics miss the signs.

The pictures you see are deceptive:
Removing the fenders, hood and interior was easy, just took time.
Cutting metal and removing the rubber undercoating took almost half my time.
Making templates and forming new metal is fairly quick.
Welding on a Mercedes is a PIA because of the respirator to protect against toxic paint/rubber vapors, good ventilation and a strong fan helps.
Welding on this car used up four respirator cartridges.

[leathermang]

I did not know you had access to this car WHunter.....
and I assume you have a wire mig you use for welding in places like this....
But even so...your correct description of the PIA factor with regards to welding on the floor of a MB make me think that if there is metal sufficient to support positioning of things like the mat I mentioned from the POR15 people that that is the way to go on this type situation.
No chance of fire either.
Still requires good ventilation and proper respirator in a closed area....
Large unsupported areas of weight bearing sheetmetal typically are beaded to give them rigidity..... do you have a beader ?

Beader example:
www.mittlerbros.com/Beadroller.htm