Ultra Super Ghetto Rust Repair

My Daewoo of Death had a rust problem. First, the passenger side rear strut tower rusted through. Fixed that. The driver's side rear strut tower followed a year later. Fixed that. Then there was the sill on the driver's side that didn't look that bad and it wasn't functional and who cares it's a damned Daewoo.

However, this week I took a wire brush to this little bit of rust and discovered a collection of absolute horrors. The sill was packed with salt and rust - there must have been five pounds of loose crap I pulled out. Someone's idea of a "repair" in the past had evidently been to stuff the sill with cardboard and then slather a bunch of bondo OVER the rust. Once I got through the bondo I found four separate holes completely rusted through and the cancer was getting close to affecting the structural parts of the unibody.

So I panicked. I pulled out the cutting wheels and sliced off everything that looked even slightly suspicious. I was in that fugue state of mind where you are somehow both aware and unwilling to admit that you should probably not be cutting the bodywork off your daily driver with an angle grinder.

I spent the next couple of days driving around town with enormous grinder-holes in the sill, collecting necessary tools and materials, doing grad school stuff and reading Joey M's 32 Datsun build thread. I also used a pressure washer to clean out any remaining gunk I couldn't get with my fingers.

After several unsuccessful trips to used furniture stores, apartment complex trash heaps and the construction zone around a local middle school, I finally stumbled upon a recycling center that looked promising. I talked to the owners and after a little finagling they agreed to let me poke around their scrap piles. There, glimmering among the decaying refrigerators and toxic sludge puddles, was a glorious heated floor panel. It was perfectly flat, made of stainless steel roughly the same gauge as Daewoo body panels and mine for the princely sum of $1.78.

I took it home, cut it into strips and removed all the electrical/foam/thermal gubbins. With the materials ready I once more went into my apartment's underground parking garage, pulled out my collection of hammers, fired up the drill and prepared the rivet gun.

Basically I used the original body structure to provide a shape and then drilled holes into the good metal surrounding the voids I'd cut out. I then riveted the patch panel into place along the top edge, bent the patch around the remaining structure and then riveted it onto the bottom of the sill. After about three hours of grinding oil, sand and steel dust into my armpits, the whole thing looked suspiciously like a healthy sill.

Granted, the color isn't an exact match (gold patch, white car) and the panel doesn't perfectly blend with the original sheetmetal, but I think with a little bit of correctly applied bondo and a respray (which the car badly needs anyway), it will look pretty respectable. Pictures of this part coming soon.

My questions for the great GRM braintrust are thus:

1. Did I do anything fatally stupid?

2. Am I going to get a stainless/mild steel galvanic corrosion fuster-cluck of doom?

3. If I drill an access hole or two into the patch and fill the sill with expandable urethane foam to make it more weather-proof/structurally supported, will this have horrible unforseen consequences?

1. Don't think so
2. Don't know, thus the answer to #1
3. Possibly, it can trap water and accelerate the rust. This is a good ghetto frame stiffening trick, but I'm not so sure it's a good idea in the long term.

HOw long do you want to keep the car and do you have any kind of inspection there. In England you wouldn't even be allowed to think about driving the car on the road in that condition. Here in Michigan at least you see vehicles with absolutly no rocker panels /sills left at all driving for year after year. We have right here on GRM a rather famouse case of making Miata rocker panels out of great stuff expanding foam, bondo and paint.

It all depends on how long you want it to last. I'd say there is no way you'll keep the water out with the current repair and in the end you'll end up rusting out more. But if you want to make it look resonably tidy for a year or so, spray it with some chip guard / underseal and call it good.

The car is hopefully about a year away from being taken completely off the road and used exclusively for racing. It won't be a problem with inspection even if I just let the sills rot off.

Is there any good way I can make it water-tight? That's what the urethane idea was for, but I don't know if that will work.

In reply to DaewooOfDeath:

Ask oldtin about his ti of horrors rust issue........don't use expanding foam, period. Even if you could get a perfect seal, the metal will sweat anyways.

Foam inside is a bad idea. It is impossible to seal water out, so you need to let it back out. Just drill a couple of small drain holes.

Hang on, you want to race this? As in on a track not an autocross type environment? If so the only way to fix this is properly. Cut out the all the rust. Treat all bare metal and weld in new. Preferably a complete new sill/rocker not patches. YOu don't want to find yourself on the inside of an acordian if you hit the wall.

Adrian_Thompson wrote: Hang on, you want to race this? As in on a track not an autocross type environment? If so the only way to fix this is properly...don't want to find yourself on the inside of an acordian if you hit the wall.

This.

The sills are a structural part of the car. Fix that E36 M3 correctly.

Badly rusted cars will completely fall part if you hit something (or something hits you).
Just take a walk through your local salvage yard and that E36 M3 will scare the E36 M3 out of you.

to slow the rust down, drill a couple of holes and spray liberally with PB rust stop. And please do fix tghe rust correctly before putting it on the track.

Adrian_Thompson wrote: Hang on, you want to race this? As in on a track not an autocross type environment? If so the only way to fix this is properly. Cut out the all the rust. Treat all bare metal and weld in new. Preferably a complete new sill/rocker not patches. YOu don't want to find yourself on the inside of an acordian if you hit the wall.

Even with a cage?

The rusted out part I patched didn't look very structural to me. It abuts the frame rail, which isn't damaged. I know because when I cut away the outer part, I could see the entire frame rail.

Maybe I'm using the wrong term here.

Imagine the thin sheetmetal that would normally cover the freshly welded structural sill in this picture. That's what I ghetto repaired, not the structural part itself.

Just to clarify, if I'm wrong, please tell me. I don't know what I'm doing nearly well enough to argue with you all.

From your description it sounds like the part you repaired isn't structural, on some unibody cars it is though. On those cars the sheetmetal sill loops around to form a "rail."

But if the outer is rusty, what is really the condition of the inner structural part. If your going to race it then cut it all out and start with fresh material