Rust repair on passenger door

[Christien]

I have some rust starting to bubble through the paint on the bottom from corner of the passenger side door. The area is maybe 3 or 4" square. I had a small leak in the bottom right corner of the windshield (sealed now) which would drip underneath the glovebox, and I'm willing to bet it's related.

I've never done bodywork before, but I'm willing to tackle it over the winter. I just picked up a welder and compressor (with painting tools) from my brother in law.

I realize that there may well be much more rust that what I'm seeing, but as for this part itself, what is the basic process? I'm thinking cut away the corner and weld in a replacement piece from a donor door, sand and paint. Is that the gist of it?

[bkreigsr]

what year? - makes a difference. Bill K

[wachuko]

Depending on the extent of the damage you could just use some generic metal stock and rebuild it... or, worst case, get the part from our host. I just did that for my SC->RS project.

Repair panels for the passenger door arrived today. Will take them Saturday to the shop.

[Christien]

Originally Posted by bkreigsr

what year? - makes a difference. Bill K

I was about to make some wise-ass remark about looking at my sig, but then realized it's disappeared for some reason! That's weird - it seems to be only on that post. When I look at other posts of mine, my signature line is there. Hmm.

Anyway, it's a 1972.

[bkreigsr]

My 73 had some rust bubbles on the same door when I bought it in 1979. I sanded and patched with body filler (1979), and let it go at that. The inside of the door cavity had zero rust. The repair is still intact, and hardly anyone notices - doesn't bother me and the car retains the original paint.
Bill K

[Christien]

Wow, your car is mine's twin!

I'll take a pic and post it when I get home.

[Rotmilky]

Originally Posted by Christien

I realize that there may well be much more rust that what I'm seeing, but as for this part itself, what is the basic process? I'm thinking cut away the corner and weld in a replacement piece from a donor door, sand and paint. Is that the gist of it?

Yea, that's pretty much what you need to do. And with a 72, you'll likely find some more rust. Might as well put that welder to some good use and practice on a door before you find you'll need to weld on a complex piece in the bottom of the smuggler's box.

I'd suggest you practice on some sheet metal first to get your confidence/skill up and get your welder set up right. You should be able to pick up some 20 gauge sheet at the local hardware store. Cut off a chunk and weld it back on. Dress the welds to your desired finish and then beat on a bit with a hammer. You want to make sure the welds are getting good penetration. If you're not getting good penetration, the dressed welds won't be very thick and will crack when you hit it with a hammer. For weld dressing, I like to use a course grit lapped sandpaper wheel on my grinder. They cut much faster than my solid grinding wheel. Keep cutting off chunks and rewelding them on till you feel you want to start cutting and welding on your precious car. That, for me, was probably the scariest thing.

As to the welding itself, many people use a skipping technique to keep from building up too much heat. Basically weld about 1 second in one spot. Skip ahead an inch or so, and repeat. Keep going around until you've closed in all the gaps. Dress the weld. Fix any pinholes with more welding. Redress.

You might take a look at the restore threads on the forum here to see what some people are doing. It's nice to see someone else repairing a piece that you need to fix. And post up your work here. There are lots of people on this board who have had to do lots of rust repair that are willing to offer help and support. I find their input very valuable.

[ossiblue]

Your original post does have the gist of it--cut away rust, weld replacement metal, finish/paint.

The difficulty of your task will depend on the degree of rust, as you know. Bkriegsr's patch was effective because the inside of the door was rust free so his bubbling was probably due to paint failure so a surface patch worked. In your case, you should first closely inspect the inside of the door. If the rust you need to fix is from the inside to the outside, you have major surgery to perform--cut out, weld, etc. The amount of rust and the area it covers will determine if a simple DIY patch will work or if it's more practical to buy a formed panel. Regardless, the procedure is the same but if you're a novice on sheet metal work you may wish to consider a pro for the repair if it covers a significant area. DO A LOT OF RESEARCH ON BODYWORK and decide if you want to tackle the project. It's simple in theory but can be difficult in execution.

[sballard]

Christien-

Here is a link to a great webpage by DarrylD, who used to post a lot about his 912 project. There is a wealth of info here. This link specifically describes his door rust repair, but I recommend going through the entire project. Fantastic stuff.

DarrylD's Porsche 912 Project Page - Phase 7: Right Door Skin Bottom Edge Replacement

Good luck!

[Christien]

Originally Posted by ossiblue

In your case, you should first closely inspect the inside of the door. If the rust you need to fix is from the inside to the outside, you have major surgery to perform--cut out, weld, etc.

When you say inside, do you mean the surface showing behind the interior door panel, or deeper inside the door? I replaced the door panels just about 6 months ago and there's no rust showing on anything I could see from that side.

[ossiblue]

Originally Posted by Christien

When you say inside, do you mean the surface showing behind the interior door panel, or deeper inside the door? I replaced the door panels just about 6 months ago and there's no rust showing on anything I could see from that side.

I meant the inside of the outer skin as the doors typically rust from the inside due to the water that passes through from the window opening. If you removed the door panels and looked down at the bottom of the inside of the door and all along the seam of the bottom where it joins the outer skin, then you've inspected the area. Be sure you get a good look with a strong light and maybe a mirror to be sure. Any suspect areas should be probed to see if there is rust.

[Christien]

Pics:





From the inside:




From the underside:



Again from the underside, I'm wondering about the tiny little bit here - didn't notice it until I looked a the pics on my computer:

[ossiblue]

I'll guess if you remove the door panel and look in the space between the inside frame and outer skin that you'll see rust down there. The bubbling you show on the outside is typical of the rust-through from the inside channel. Could be wrong, but you won't have peace of mind until you do a thorough visual of the inside of the skin.

Now, all that being said (to prepare you for the worst case scenario), it's still possible the bubbling is from the break in the skim coat and is limited to the outside--between the skim coat and the skin. If your interior inspection shows a clean, dry inner skin, you've been given a break and your repair to only the outside will be much simpler. You will have to remove the skim coat regardless and when you do, you should be able to tell if there is rust through to the inside and if you'll need to cut and weld sheet metal.

[Christien]

Ok, I'll have a look. When I start tackling this, am I best to go at it at first with a grinder? Or just skip right to cutting? Or will what I find on the inside determine that?

[ossiblue]

Originally Posted by Christien

Ok, I'll have a look. When I start tackling this, am I best to go at it at first with a grinder? Or just skip right to cutting? Or will what I find on the inside determine that?

Your inside inspection will give you the best idea on how to proceed. I would never just skip to cutting as you need to determine the extent of the sheet metal rust and that can only be done after the paint has been removed. Rust is the "iceberg" of the sheet metal with generally one tenth being visible (bubbles) and the rest hidden under the surface.

If it were me, I'd do the inside inspection followed by a prying away of the skim coat at the immediate areas of release (the corner and the bubbles), followed by grinding/sanding the area around all suspect parts down to bare metal.

[Christien]

Ok, thanks. That's a good start for me to begin getting my head around this. I'm not starting until after christmas - lots of reading and learning to do before then!

[bkreigsr]

Bad news, that area is breaking down as a result of the prior repair. The peeled surface is actually a bondo type filler layer seperating away from an ill-prepared base metal surface. There is also decay at work further along the door where a similiar reaction is occuring under the bubbles. I would carefully inspect, or have a good shop inspect, for further panel repair with the bondo type fillers.
Bill K

[ossiblue]

Good eye, Bill.

Yes, I agree with Bill's assessment but that may turn out to be good news, depending on why the repair was made. No use is speculating, however. When you open up the bubbles and begin to strip away the paint/filler, you will know the extent of your repair needs.

Though you don't plan to start until after Christmas, you can still do the interior door inspection now. It will be interesting to know if the door interior is clean and dry. Please keep us informed.

[Christien]

There are several bondo repairs on the car, as evidenced by a magnet. Who knows why - it was all before my ownership of it. I do know that the guy who owned it before me had a cheap paint job done. No idea if there was any bodywork then, or if it was just a respray. I do know it's lousy paint - the hood chips very easily and there's orange peel everywhere, as well as overspray in places you really wouldn't expect it.

I can see how that might actually be good news, if it was just poorly bondo'd and needs to be redone, rather than having to cut and weld. Either way, I'm prepared to cut and weld, so it can't be any worse than that, right?

I'll see if I can get some time this weekend to pull the door panel off and poke around.

[AVDCAV]

Start looking for a new door or reskin it
That door s a plastic rusty mess
Use as a last resort.