w123 Floor Rust repair - PeachParts Mercedes-Benz Forum

martureo · #1 03-12-2020, 03:18 PM

My daily driver (1984 300D) had a leak into the interior from corrosion behind the battery. This led to the passenger rear foot well having a rust hole which I discovered by pulling up the carpet one day.

The entire seam between the floor and the rocker panel up to the front wheel well decided to rust out as well. I managed to park the car for a few days and weld in some new metal and new rubberized undercoating, but just finished it enough to get the car back on the road.

Fast forward to a year later I find the driver's rear floor carpet soaked. I dry it out, no rust to be seen. A month following that I notice that my right foot is cold and the pedal seems soft. Check underneath the car and the pedal mounting tab has rusted through the bottom of the car.

While I'm trying to find a place to store the care while I fix it, I'm driving long distance on business and the driver's seat leans a bit too far in one corner. Yup. The right rear seat mount has also rusted through the floor.

Time to fix it all.

So here's the damage.

The pedal pulled out of the body without any force. I just detached it from the linkage rod. (Yes, that is undercoating on the bottom)

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Once I removed the driver's seat, carpeting and chiseled away the asphalt sound insulation. This is what I found.

And after the partially rusted out seat channel was removed.

martureo · #2 03-12-2020, 03:21 PM

Since I didn't know initially what parts of the floor were still metal and which ones were just undercoating and sound deadening material sandwiched around rust, I ordered both full floor pans and the passenger side rocker panel.

I cut out a decent amount around the pedal, with both the depressions for the pedal and fuel lines collecting sitting water. This is almost fully welded in. I'll take more pictures after it's ground and sealed.

Here's the patch underneath the seat. Only partially welded at this point.

vwnate1 · #3 03-12-2020, 06:34 PM

RUST NEVER SLEEPS .

Who makes those patch panels ? .

martureo · #4 03-12-2020, 09:48 PM

The vendor (JC Whitney) I bought them from said they were Key Parts but they turned out to be Klokkerholm.

Each pan was $78
The rocker panel was $40
Shipping was $79

Total of $292 after taxes. Totally worth it.

barry12345 · #5 03-12-2020, 10:21 PM

You probably know this. Protect the glass when grinding. The sparks can melt into the glass. I try not to learn things the hard way but there are exceptions over the years..

martureo · #6 03-13-2020, 09:11 AM

Quote:

Originally Posted by barry12345

You probably know this. Protect the glass when grinding. The sparks can melt into the glass. I try not to learn things the hard way but there are exceptions over the years..

I completely forgot that. Although I'm grinding in an area that's pretty shielded, I'll be covering the glass now.

dennislarock · #7 03-12-2020, 11:20 PM

Awesome job... on all levels!!!!

Diesel911 · #8 03-13-2020, 01:35 PM

How about a picture of the welding machine.

For other peoples info. I read that if you put a Copper bar behind when you welding thin material it decreases the chance of burning a hole through it.
I bought a bar of copper 6x1 inch 3/16 thick. And tried that using a Flux Core welder and it helps a lot. However, you have to be able to keep the bar up against the back of the metal.

t walgamuth · #9 03-13-2020, 01:57 PM

Good work M!

vwnate1 · #10 03-13-2020, 07:18 PM

So then ;

The metal is good quality ? .

martureo · #11 03-14-2020, 11:20 AM

Yesterday's progress.

Cut a section of rust out.

In goes the patch. (about 2 hours to get it to fit well) Coated it with weld thru primer.

Those are magnets I bought to hold things in place. Got them from Eastwood. Totally worth purchasing.
https://www.eastwood.com/stitch-weld-magnets.html

Tacked in. Now about a thousand stitch welds and we can grind it smooth and get on to the next patch.

martureo · #12 03-14-2020, 11:22 AM

Quote:

Originally Posted by vwnate1

So then ;

The metal is good quality ? .

The stampings aren't exact and you'll have to work with them a bit to get them to fit the factory metal. I'll try to grab some pictures of the complex curves that don't really work.

But as the factory metal is over ten times as much... yeah, its good enough.

JB3 · #13 04-04-2020, 01:11 PM

Quote:

Originally Posted by vwnate1

So then ;

The metal is good quality ? .

Its a half to a 3rd the thickness of the original sheet metal, but welds decently. It does tend to rust extremely quickly, so needs to be well painted.

Some of the stampings are quite worn, body curves might be sloppy and need considerable work to really look good. For the floor pans its great

The great thing is that patch panels actually are available for these old cars at a good price

vwnate1 · #14 04-04-2020, 01:28 PM

Thanx for the up date .

There are a couple of U.S.A. patch panel manufacturers left, I don't know their names, sorry .

JB3 · #15 04-04-2020, 05:19 PM

Quote:

Originally Posted by vwnate1

Thanx for the up date .

There are a couple of U.S.A. patch panel manufacturers left, I don't know their names, sorry .

My understanding is everyone selling anything for 123s and 126s are selling klokkerholm panels under a dozen different names and prices. They seem to be the world source for old mercedes.