Rusted section of rear fender lip

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Some of you know that I was removing the fender lip trim. The driver's rear fender was hiding a rusted and badly repair section small enough to be covered under the trim. After all these years I have repaired a lot of rust in internal areas were aesthetics were not that critical. This is my first endeavor  of a exposed body panel so I am a bit nervous. Last night I removed the paint and the bondo that was hiding the thru-holes. I would like to clean the area as best as I can before I take it to a body shop to repaint the section. I don't want to repaint the whole body panel, but maybe they can do the lip and blended into the fender. As I have said, mine is not a show car, but more of a 20ft away good looking car.

Options I am thinking now:

1- Cut some of the inner fender to clean the area, cut as little as possible from the outer fender area around damage, neutralize, but how do I cover the openings? I don't feel proficient enough welding an exterior panel without making it worst. Should I cover the hole with bondo after rust bullet?

2- Leave as is, use a rust neutralizer and bring it to body shop to repair.

3- A combination of 1 and 2.

After removing trim:

20211209_225837.jpg

After some cleaning up. I got most of the bondo out.

20211212_230458.jpg

Interior fender from wheel well:

20211212_230544.jpg

 
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Cut out the hole and weld in a patch.  Just cool with wet rag after each tack. I would not just cover with bondo. It will bubble back out in no time. Here’s a few pics of almost same repair I did on yellow Mach. A good body shop can blend the quarter panel.  Sorry my pics are mixed up but you get the idea  F6C4652C-963E-4BA7-8300-1BEAC2D37196.jpeg 81FAD34F-A342-4E02-B650-7C162E64B7B7.jpeg DCFA7C15-7DD0-4080-9B1F-82977B986EB9.jpeg

3FA52E7A-DF20-4EF9-A74A-947AD787643B.jpeg 3D69BA0E-3AD0-4FFC-B6CB-D8F279E7A69F.jpeg E91C62D2-055B-4A79-8177-57BC7E36D09E.jpeg D920AA1F-6AC0-4FAE-AFF1-A6B36349A196.jpeg 53D7A9D6-2F40-422D-8306-F70CEE32F4B3.jpeg 718BE00C-D34B-4DF4-8169-4405082D975E.jpeg

 
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Cut out the hole and weld in a patch.  Just cool with wet rag after each tack. I would not just cover with bondo. It will bubble back out in no time. Here’s a few pics of almost same repair I did on yellow Mach. A good body shop can blend the quarter panel.  Sorry my pics are mixed up but you get the idea  
Thanks. I don't know if I trust my welding skills for exterior panels. In my case, the good thing is that the rust is only in the lip area so it may be easier to blend the paint along that edge. That said I would like to keep any damage within the lip but the heat of the welding may extend past that edge which will make it more expensive/difficult to blend the paint. 

 

71Rustang

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I echo everything ,Turtle5353 wrote.Cut it out. When welding on exterior stuff I use an air nozzle instead of water,to cool the panel. Yes the heat will screw up the paint,but that's just par for the course.  The fender lip has a lot of strength to it,so it will resist  warping with heat very well,but still as you weld try and keep it as cool as possible. 

 
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I forgot that I have the inner wheel well that I bought when I worked on the trunk. Back then I only used the section facing the trunk. I could use a section of it to match the piece that I would have to weld. I can't weld as you guys but maybe I will give it a try. Should I weld the inner sheet metal first, or the outside, or it doesn't matter? What do you do with the backside of your welded metal, can you prime it from inside the car?

 
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I would cut out the rust hole on the lip of the wheel well a bit bigger than the rust hole.  Cut it big enough that you can then cut the rust on the outer wheelhouse and still have room to weld the outer wheelhouse patch in.  Once those welds are ground down, you can make a patch for the outer skin.  Don't skimp.  Making the patch a bit bigger than you need will make sure you get all the rust out.  Don't worry about keeping it small to minimize the painting needed.  It will be blended out a foot all the way around the patch, so an inch or two on either side doesn't really matter.  

If you're unsure of your welding skills, watch some YouTube videos (JoDaddy's Garage and Fitzee's Fabrication are two great ones) and then practice, practice, practice, and you'll get there.

Best of luck.

 
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Here is my progress. I cut past the damage and I am now in solid metal.
I have a couple questions for the experts:
-As you can see there is a "thin" layer of bondo between the fender and paint. This area was definitely involved in some kind of accident since the sheetmetal is a bit wavy and then it was smooth out with bondo. After I weld my patch, will the shop need to re-bondo that area to make it level with the rest of the painted surface. I don't want to go down the route of redoing the whole fender.

-Given the above issue with bondo, how should I bring it to the shop? As bare metal after welded/ground, or painted with a coat of rust bullet or similar? 

-When you guys weld a sheetmetal panel and then grind I see that sometimes the surface is not perfect. Sometimes there are a few indentations in the areas welded. How do you smooth out these?

20211215_234144.jpg

20211215_234030.jpg

 
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The pro-answer to this would be filling the intendations with lead (or artificial lead like metal epoxy as today used, me too), sanding, then metal Bondo, sanding, then Fine-Bondo, filling the last little imperfections, sanding, then filler or primer, sanding, body color, clear coat. 

This would include sanding the whole quarter panel until there is no old Bondo. Because you don't know how the old Bondo will react with the heat of your weldings, the new paints and primers and Bondo... So it could be that there will some cracks to see soon... 

As you don't want to go so far there would be some risk. I would do the whole thing by me and only let blend the body shop in the color. If not let the body shop do the whole thing until now by them. 

If you want to do a mixed up thing - please no offense to you, sometimes things have to happen these ways, we all know it - then weld it, sand around your welding location until you have solid Bondo on solid unrusty metal, then apply a light coat of primer to prevent flash rust. As body shops like to use their own materials they only have to sand slightly when it's the turn of your car... 

Just my 50 cents based on several years experience of body work in different stages with all possible scenarios on my Mustang... 

 
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I agree with Tim, the bondo near of the weld may lift up.
And for them its not like sanding a greater area will affect the price, this will allow them to use much longer sanding blocks and give you better results.

If its metallic paint, they will need to spray a larger area anyway unless you don't mind have a visible difference. The top coat might even become far greater if you want all blends nicely. All side reflections are on the higher quarter and you want to blend at body lines.

For the welding, keep in mind that bits looks straight but its not and because the wheel arch is curved on one axis only, I'd personnaly make a template of the lip/arch, then once you have the patch fiting nicely with extra length on the lower side, cut the lip and weld a flat part on that first patch. the beads becoming material to grind and will give you a solid and good looking shape. rather than trying to weld that already weak lip to the new piece.

Search for Fitzee on you tube, the guy uses this technique extensively (a bit too much for my taste at times) but is ideal for this specific patch.

May be, now that you have cut the inner side, I would actually cut it a tad more, allowing you to place copper/brass behind while you weld the outside to absorb the heat. It's easy to make a hole vs weld on old to new metal patches:)

Good luck!

 
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Thank you for the replies. I was going for the mixed option (no offense at all Timachone). I still don't feel confortable with welding an exterior panel. I may just take it to the shop for them to do what they need to do. In any case, I won't be working on it until January.

 

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Please don't use the product BONDO, as it is cheap and a crappy product.  There are many others that are much better as metal fillers.  RAGE comes to mind, but it has been 7-8 years since I last did metal work.

 
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I agree with Randy, Rage filler is excellent to work with and in my opinion is a better product.  Tony, if you are really uncomfortable with welding on outer panels, have you thought about tack welding a couple smaller pieces of metal to the ends of the hole that you cut so that they are on the inside, then using some panel adhesive like 3M makes, then a small skim of filler to smooth it out?  I couple quick tack welds to hold the inner ledge in shouldn't affect current filler on the panel and you may avoid any warpage. The size of this repair should be pretty easy for the panel adhesive. Thoughts?

Tom

 
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Please don't use the product BONDO, as it is cheap and a crappy product.  There are many others that are much better as metal fillers.  RAGE comes to mind, but it has been 7-8 years since I last did metal work.
I think that most of us use 'bondo' as a synonym for any type of filler paste. So was me. I recommend using high quality products. My fillers I used were with metal particles and are up to 40 - 60 bucks per unit. With standard filler aka bondo I only filled the last small pores in the other fillers before final primer and paint. 

I used as less as possible but in body work there is almost no chance to go without it. At least on my car it upholds for years now without cracking, warping, bubbling etc. But I gave the hole bodywork months for sitting and drying - time a normal bodyshop don't has...

 
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I have been going back and forth with my options. This is one of the great things about this website. Reading all this is encouraging me to try. I really don't have much to lose. What is encouraging to me is that the exterior panel is backed up against the interior panel which I think should make welding the exterior panel easier. I will first do the interior panel which doesn't need to be perfect since it will be covered with undercoating. Once the interior panel is welded then I can proceed to the exterior which is almost touching. Due to the proximity I can see that the interior and exterior panels may be partially welded together. Once completed I will have to pour some primer/rust protection in this gap from inside the car. I think my job is easier since I already have the inner fender panel leftover from when I fixed the trunk/fender area.

 
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After debating for a while and talking to the bodyshop I decided to do it myself. Bodyshops don't want to fix fenders just replace, which is not an easy task in our Mustangs. After convincing them on fixing it, and being told that they are not responsible for rust fixing they wanted to paint much of the rear for color matching. I can understand their perspective. However, I figured I didn't have much to lose and decided to do it myself.

After cutting all the rust away I welded sections of sheetmetal on the outside and inside. After grinding most of it I covered it with Rust Bullet. Then smoothed it out with some filler. Then some epoxy primer and sanding, then some high fill primer and sanding, then a coat of brushed on Ford Blue 6 touch up paint and sanding, and a final coat of Ford Blue 6 spray paint. I can see the difference but it is not that obvious and 90% of the people wont' notice it. I am very happy on how it turned out. Not perfect but good enough. Let's hope it can last a long time. I still need to lay some clear coat spray. I need to find a good one that I can use to match.

After cutting all the rust and more:
20220103_210440.jpg

After welding. I am no expert when it comes to thin body panels. Looks ugly but it was all covered. On the inside part I spot welded about a 1" apart and then sealed with seam sealer.
20220305_164731.jpg

After grinding. No need to go all smooth since I recessed the patch a little:
20220305_174522.jpg

After Rust Bullet:
20220308_223847_resized.jpg

After filler, epoxy primer, sanding endless times, touch up paint and spray paint (sorry no in between pictures). You can definitely find it if you know where to look.
20220430_172518.jpg
 
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Sheriff41

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Nice work, Tony! You'd have to really be looking for the repair to even notice.
 
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