Paint and Body Chythar's 94 Cobra Clone Paint thread

Chythar

Recently finished repairing my rear
15 Year Member
Aug 26, 2004
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West Los Angeles, CA
I guess it's about time I made this post. I've had this all ready to post a few times, just to lose inspiration and shelve it for a while. But here we go.

I've spent time during this pandemic learning how to do body work and paint, practicing on my 94 Cobra clone, and was able to fix its damaged rear quarter panel. That thread is here - https://www.stangnet.com/mustang-fo...iring-my-94-cobras-rear-quarter-panel.920903/ I learned a lot fixing that rear quarter panel - mostly things NOT to do. Most of the problems I ran into wouldn't have happened if I just done two things: a better job sanding at the primer stage, and laid down thicker paint when I sprayed the topcoat. But sometimes, you learn more from your mistakes than you do if you did things right the first time.

Now, it's time to apply those lessons and repaint the faded black paint on the car. I have the skills and the knowledge, but I lack enough practice to get a consistent result. I also don't have a large painting booth where I can paint half the car at once. Thus, the plan is to paint one or two parts at a time. This will not only give me the practice I need, it also lets me fix any issues on a single painted part. That way I won't spray the whole car wrong and have to do it all over again. I used cheap paint to practice with, but the new stuff is much more expensive. I want to waste as little of it as possible.

I have a used 'COBRA' rear bumper that I've wanted to put on the car for a while, which made it the perfect part to start with. However, it's been painted with some rattle can paint that was supposed to be Ford UA black. Sadly, the paint had some sort of metallic flake in it. Thick paint on a bumper tends to crack, so I need to take that paint off before respraying. I started sanding, and realized I had laid the primer on pretty thick. Since I originally painted this bumper, I've learned a LOT more about sanding and prepping primer and paint. I decided it was better to start over and strip everything off the bumper. In hindsight, I am so glad I did that - even though it cost me a lot of time and money.

I used acetone and a lot of the blue shop paper towels to dissolve the paint and primer. This first photo is partway through that process. Feel free to ignore the laundry basket and the nosy cat.

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Chythar

Recently finished repairing my rear
15 Year Member
Aug 26, 2004
2,353
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West Los Angeles, CA
Not surprisingly. the acetone fumes were pretty strong in the house even though I had a fan blowing. So I stopped and set up a temporary painting booth that I've used several times in the past. It's made out of a wood frame and thin plastic sheeting stapled and taped to the wood. It's just big enough to fit the bumper in at an angle, with enough room left to move around the bumper without touching it. I have a small enclosed back yard that's part of my apartment, so that's where I set up the painting booth. Here's a shot of the assembled frame. It's made up of 1x2 strips that I've re-used many, many times over the years.

20210615_164534.jpg


Next up is the plastic sheeting. I have no weather-safe place to store the painting booth, just outside. The plastic sheeting eventually gets brittle and breaks, so it has to be replaced. The plastic you see is one continuous piece wrapped around the top, sides and bottom.

20210615_170812.jpg


Finally, finished. I laid separate pieces across the back and the front. The front piece is rolled up for easy access. When I paint, I use spring clamps to hold the front flap closed. It's not a perfect seal, but it's very close and more than good enough for painting.

20210615_175613.jpg
 

Chythar

Recently finished repairing my rear
15 Year Member
Aug 26, 2004
2,353
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West Los Angeles, CA
I finished stripping off the old paint, or at least everything that the acetone would melt. And found a lot of hidden damage. I originally bought the bumper several years ago from a guy on the Corral. He said the bumper was in good shape, primed and ready for paint. With everything off that the acetone would remove, I can now see that was a bald-faced lie. The bumper is badly warped in the middle, and someone used a lot of primer to fill it in. I knew the 'COBRA' letters were kinda warped, but at the time I figured it was no big deal. These bumpers are really hard to find, and I got it for a really good deal, so I figured I could fix the 'minor' issues. In the photo below, the three green pieces of tape mark three major low spots in the bumper. Those low spots are partially filled in with Bondo Bumper Filler, a flexible two-part epoxy that's intended for bumper repair and as filler. This is different stuff than the regular Bondo, it's sold specifically as flexible bumper repair. When I bought the bumper, I had never seen a Cobra rear bumper before so I wasn't exactly sure how it was SUPPOSED to be shaped. Were the low spots I felt supposed to be low, and the high spots to be sanded down? Or should the low spots be filled? Or both? I'm really slow at this part, trying to figure out what the proper shape should be. My technique is to add some filler and shape it a bit, then repeat until the area FEELS right.

And there's still a lot more that's wrong with this bumper.

20210618_164316.jpg


I really thought that this bumper was ready for paint, but there's so much to fix now that I can't think about painting yet. And I ran out of the Bondo epoxy; they're small tubes, so no big deal. But with the pandemic, no one has any in stock. Not even Amazon. I had to go to eBay to buy more. This is already raising red flags with me - a bumper that was 'supposed' to be good, needs this much repair? Something is very wrong. I decided to do some internet research while I waited for the epoxy from eBay to arrive. It took a while, but I found some close-up photos of Cobra rear bumpers. Most were from eBay auctions selling 'COBRA' inset letters, but some were from 95steedamustang's 94 Cobra build. The photos told me this - the bumper should be shaped just like all the 94-98 bumpers, except for the 'COBRA' letters in place of 'MUSTANG' or 'MUSTANG GT'. No added curves or fancy shapes to further distinguish it from other bumpers. The bevels around the letters seem sharper than on the other bumpers, but that's another issue I haven't gotten to yet. Now that I can compare the shape of the Cobra rear bumper to my existing bumper, I can tell what's wrong. The low spots are really low, and one of the high spots might be too high. The bondo'd spots are getting bigger as I try to fill them in. AND, I found another high spot. Check out the new sanded area.

20210704_190030.jpg


I don't have a photo of it, but I know how the bumper got warped. There's some filler in the back of the bumper, looks like that spray foam in a can. I'm guessing the previous owner didn't want the bumper to warp, so he filled in the back with spray foam. Problem is, that spray foam gets really hot when it cures and it warped the bumper badly. He tried to fix it, then dumped it off on some sucker that didn't know any better. And this time, that sucker was me.
 

Chythar

Recently finished repairing my rear
15 Year Member
Aug 26, 2004
2,353
134
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West Los Angeles, CA
I hadn't given up on the bumper yet, and I kinda couldn't since I couldn't find another Cobra bumper for sale. Hand sanding was taking too long, so I broke out my power sander with 80 grit sandpaper sheets. It did a great job on paint and the cured bondo, but not so good on the urethane.

20210704_193725.jpg


At this point, I've run out of the Bondo I bought off eBay and I'm STILL not done. We're past red flags, and I've now got flashing red lights all over. I keep expecting a robot to roll up and shout "Danger danger, Will Robinson!" But again, no bumpers for sale. Even if I found a replacement bumper, it would be much more expensive than buying more epoxy Bondo. So I soldiered on. I still couldn't find the smaller syringes of the epoxy Bondo, so I decided to buy one of the larger kits I found locally. Those kits are for larger repairs, and require you to mix a lot of epoxy together at one time. If I didn't use one of those kits, the project would stop until I got more from eBay. So I bought the kit. I mixed the two parts together, and there was so much epoxy I could easily fill in the three low spots. And I still had a lot of mixed epoxy left that would go to waste. I used most of it to fill in the spots between the letters as they were low spots too.

I waited a couple of days, then checked to see if the epoxy had cured. It should have cured in minutes, but I laid it down pretty thick. I could see streaks of two different colors of gray in the epoxy, a sure sign I hadn't mixed it well enough. Crap. Time to test if the epoxy was either strong enough, or I'd have to take it off.

Oops.

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Double crap. Gonna have to scrape off all the gray epoxy. The stuff from eBay mixed well and dried black instead of gray, so I figured I'd only have to scrape off the new stuff. Boy, was I wrong.

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That's all of the epoxy I put on. ALL OF IT. For some reason, I thought the brown color on the bumper was urethane. Nope! It looks like it was the factory primer, as the only thing under it is the cream-colored urethane. The epoxy attached really well to the paint, and the paint came off the urethane real easy with the scraper. However, some of the epoxy was laid down on the urethane directly and it did NOT want to come off. I'll have to sand it off. But this means I have to start all over again.

I couldn't.

I just couldn't.

Yes, I can properly strip the bumper down to the urethane and buy more epoxy. But even if I replace what came off, it's going to need a LOT more. And I'm having a hard time finding more epoxy. Even if I could buy more epoxy cheap, I could still spend $100+ on epoxy to fix this bumper. And I'm not confident I can fix everything. I can see several ways of modifying the bumper so it would look good, but it wouldn't be CORRECT. And that would bother me a lot. So I put the project on hold to figure out what to do next. I should have started sanding the front bumper, but eh.
 

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Chythar

Recently finished repairing my rear
15 Year Member
Aug 26, 2004
2,353
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West Los Angeles, CA
After several Google searches, I finally found one web site that had a reproduction Cobra bumper in stock. It's made by Daniel Carpenter Mustang, and it's the same one sold by LMR - though LMR is out of stock. Everyone was out of stock, except for this web site. They sold the bumper for a cheap price, but it's only shipped by truck; and truck shipping from them to me is really expensive. Then I found a used Cobra bumper on eBay. It took a while to negotiate shipping with the seller, as he would take a few days to answer an email and then he would only answer once a day. But I finally got him to agree on a shipping price. Then he ghosts me and sells the bumper to someone else. ARGH! So, back to get the repro bumper. Bought it from National Parts Depot, and this was their very last one. Whew!

Or so I thought.

I checked my bank online, and I had a refund the same day NPD charged me. I called them up, and they said they can't find the bumper in their inventory so they refunded me. Strike two.
 

Chythar

Recently finished repairing my rear
15 Year Member
Aug 26, 2004
2,353
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West Los Angeles, CA
The rear bumper issues held me up for too long, so it was past time to get off my butt and prep the front Cobra bumper for paint. This one was fun - I bought it used when I did the Cobra conversion, and the paint at the time was in good shape. But over the years (it's been 14 years since the conversion, wow), I discovered it had a clear coat when it started to peel. My Mustang did not come with a clear coat, so the rest of the black paint has faded instead of peeling. There's also a ton or rock chips that need to be sanded out. This is what I have to work with.

20210804_181334.jpg


Ick.

I scraped off what I could with a plastic scraper blade, then started sanding. Gotta sand off all the peeling clear coat, or the paint will peel again some day. Started with 80 grit sandpaper on a foam sanding block, then switched to 120 and 240 when it felt right. The Cobra is my only car, and thus my daily driver, so I'm going to sand the bumper while it's on the car. When the sanding is done and ready for primer, I'll take the bumper off and finish sanding the few spots that are left. I'll end up taking the corner lights out to sand under them, but I'll leave the headlights and the Cobra emblem on as they're a PITA to take off.

I made decent progress until my arms got tired. I'm going to try my power sander next time, but I'm not sure how much good it will do since the bumper is all curves and the power sander has a solid flat base.

20210804_193716.jpg


As a side note, the Cobra emblem is the larger Shelby emblem used on the newer cars. It barely fits in the grille, with just enough room for a piece of paper to slide between the emblem and bumper/hood. No one makes a bracket for that emblem, so I made my own. When I paint the fenders, I plan on using the same big snake emblem instead of the smaller OEM ones.
 

Chythar

Recently finished repairing my rear
15 Year Member
Aug 26, 2004
2,353
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West Los Angeles, CA
Power sanding helped speed up the sanding a lot, but I still had to do more hand sanding with 80 grit to make sure all the holes in the clear coat were gone. More sanding with 120 grit, and finished with 240 grit. Almost all the clear coat is gone, and what little is left shouldn't make a difference.

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Chythar

Recently finished repairing my rear
15 Year Member
Aug 26, 2004
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West Los Angeles, CA
Several days after I lost out on the repro Cobra rear bumper, I found someone on Facebook Marketplace listing a Cobra rear bumper in Arizona. The seller wouldn't ship the bumper, so I figured I was out of luck again. A few days later, I was chatting with a friend of mine, and I told him about the bumpers in Arizona. He offered to drive us out there to get the bumpers.

ROAD TRIP!

One sixteen hour trip and just over 800 miles later, and I have a clean and undamaged Cobra rear bumper. Finally!

For some reason, I feel rich right now.

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Your eyes do not deceive you, that's THREE 96-98 Cobra rear bumpers. The seller in Arizona had two Cobra bumpers for a good price, so I figured I'd buy both and resell one. The trip to Arizona wasn't free, gas and food isn't cheap. Any gas from the food was free, but my buddy's truck can't use it in place of fuel. He says he tried once, but refused to say anything more about it. Anyway. The white one is for sale on Craigslist, it's in the best shape. The red one is the one I'm keeping, and the damaged one will go on Craigslist once the white one sells.
 

Chythar

Recently finished repairing my rear
15 Year Member
Aug 26, 2004
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West Los Angeles, CA
It's been several months since I got the "new" Cobra bumpers. I started sanding the red bumper, and it was taking a long time to sand off the clear coat and the red paint itself. A LOT of sanding.

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After spending all that time trying to fix the first bumper, then starting over with another one, I just burned out. I'd do some sanding one day, then nothing for a week. Eventually, it got too cold for paint so I took apart the painting booth and brought the bumper inside.

I sanded all the way down to the urethane in one spot to see what the base coat color was, and how thick that base coat was. On this bumper, the base coat is black and the coat was pretty thick. This meant that I didn't really have to worry about how much of the base coat I sanded off. The thick base coat and topcoat definitely explains the cracks in the paint - whomever painted this bumper put it on way too thick. Put too much paint on a bumper, and the paint will eventually crack when the urethane flexes. But I can fix the thick paint. I've decided I'm sanding off all the clear coat and red paint, and some of the base coat too. This will let me sand out all the paint cracks and smooth the surface really well. And with a smooth surface, I can sand the final topcoat really smooth. Prep work like this is extremely important if you want a mirror-like paint finish, and that's what I'm aiming for.

One technique I used (thanks to advice from 95steedamustang) was to tape off the edges on the bumper with painter's tape. Without the tape, you'll end up sanding across the edges and rounding them off - and sanding through the base coat to the urethane. Protecting the edges is important at all stages, whether you're sanding off old paint or sanding new paint. I'm getting excellent practice sanding, so when I'm wet sanding the final topcoat I'll know the right way to protect these edges. Make my mistakes now and get a better result later.

I didn't take photos of most of the sanding and paint removal. But I've gotten a majority of the red paint removed and the base coat smoothed over with 320 grit sandpaper. Unfortunately, I've got to remove the tape I applied months ago - it got sun-baked and doesn't want to come off clean. That's not really an issue for most of the bumper, but I heed to sand the bevels around the COBRA letters and residue there IS a problem. So I've got to remove it all, then re-apply tape to protect the letters themselves. The tape you see in the photo below used to be green.

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The black is all base coat, and even if it's a bit thin in spots it's nice and smooth. Here's a side shot, and you can see some of the red paint I still need to sand off.

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The tape on the COBRA letters wouldn't come off, so I soaked it in Goo Gone for a couple of hours. Most of the tape came off, but I had to soak some spots a few times before all the tape and residue came off. I want to keep the letters red, so I'm going to tape up the letters again. Well, after I scrub off all the Goo Gone. Have a progress pic.

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Chythar

Recently finished repairing my rear
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West Los Angeles, CA
So, this brings us to today. Took a nice shot of the COBRA letters with all the tape, adhesive residue AND the Goo gone all washed off.

20220116_000326.jpg


And a shot of the sanding I did today. Taping the edge means you don't need to worry about sanding over it, you'll sand the tape off before you rub all the paint off the edge. This was with 80 grit sandpaper only; I'll sand off more of the red with 80 grit before I switch to a finer grit.

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Generally, this is how I've been sanding:

80 grit until a majority of the red is removed.
120 grit, using medium pressure, until most of the red is off.
240 grit, using light pressure, until all the red is gone.
320 grit as a final smoothing step.

If you want a nice smooth surface, which will help give you a really smooth topcoat later, you want to sand so you remove the scratches from the previous sanding. This means cross-hatching your sanding; for example, if you start sanding 80 grit in a horizontal direction, 120 grit would be vertical strokes across the piece. 240 is then horizontal; I do the final 320 grit in a circular motion, just to smooth every thing out.

I learned a lot when fixing the Cobra's rear quarter panel. The main lesson was DON'T SKIP ON PREP! I didn't spend enough time smoothing out the Bondo and the primer, then spent a lot of time on the black topcoat fixing things that should have been caught at the Bondo stage. Do your prep and fix imperfections early on, and later stages go by much faster. On this bumper, I'm spending most of my sanding time with 80 grit. It's making the later sanding stages go by much faster AND much easier.

I'm not sure how often I'll be updating this thread. The sanding on the bumper has been taking a LOT longer then I thought it would, so I'm not sure when I'll be done. To give you an idea, I started prepping the damaged bumper in June 2021; bought the new bumper that August; and it's January 2022 now. Also, I don't have a heated garage so I'm at the mercy of the weather. I live in Los Angeles, but it's still too cold to paint most days. It does jump up to the 70's now and then, so I might get a nice weekend when I can primer the bumper. We'll see.
 
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Chythar

Recently finished repairing my rear
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I didn't expect to be posting again so soon, but here we are. Today I decided to tackle some spiderweb cracks in the paint. I was sure they were just in the base coat, but I wasn't making much progress sanding them out. So I broke out my hand sander and used 80 grit pads to destroy those cracks in the base coat. Went all the way down to the polyurethane, and found out I was wrong. The cracks were in the polyurethane bumper itself.

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A quick search online told me that I had to remove the cracks completely, or they'd spread and crack the topcoat again. So, I kept sanding. After about a half-hour, I got most of the cracks out. Looks like I got lucky and the cracks weren't deep.

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I spent an hour or so carefully sanding the remaining cracks on the edges until they were gone. I can't even see a shadow of the cracks now. Whew!

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One tip I learned when sanding bare polyurethane. After some sanding, fibers in the material like to pill up and your sandpaper will stop working. The solution is to sand the polyurethane with a fine-grit sandpaper; I used 220 grit, but 180 grit would work too. The fine grit will sand off the fibers, and then your harsher grit sandpaper will bite into the surface again.
 
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Chythar

Recently finished repairing my rear
15 Year Member
Aug 26, 2004
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West Los Angeles, CA
95steedamustang told me about taping edges you want to protect, so you don't sand over them accidentally. That tip has been incredibly helpful! I don't have to worry about sanding over an edge and rounding it off. If taped properly, you can actually sand over the edges deliberately to get all the paint right at the edge. I finished sanding on both sides of an edge on the bumper, so I thought I'd show that part of the process. I removed the tape protecting the edge, and here's what I have left. The red lines are all edges that I taped previously, and I wasn't able to sand all the way to the edge. So there's red paint on the edges to clean up.

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I have these sanding sticks I bought on Amazon, and they're really helpful in this case. The finest sanding stick I have is 240 grit, but that works really well. I can gently sand over the edge from both sides until the red paint disappears. Here's a progress pic, the paint on the top edge is nearly gone.

20220121_224037.jpg


The last step is to lightly sand both sides of the edge with 320 grit to make sure the paint is nice and smooth. In this final pic, you can only tell where the edge is by the lighter shade of paint. And the most important part, I didn't sand through the black primer anywhere. :D

20220121_224042.jpg
 
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Chythar

Recently finished repairing my rear
15 Year Member
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West Los Angeles, CA
I've made a lot of progress since my last post, but it felt like I was going backwards for a while. I've finished sanding all the red paint off down to the base coat; that was easy enough. After that, I wanted to make sure that the spiderweb cracks I found were the only ones. To do this, you pick whatever grit sandpaper you want to use (I started with 240 grit) and sand that area in a single direction. Keep sanding until all of the scratches in the paint are in the same direction you're sanding in. If you find scratches that go 'against the grain' as it were, and they don't want to sand out, you probably have cracks in the polyurethane. Oh man, did I find a lot of cracks. I've already sanded them out, but here's a photo of what the bumper looks like afterwards.

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Like I said, there were a LOT of cracks to sand out. This bumper came off of a wrecked Cobra, so I'm guessing the driver's side here took a hit in the accident. There are no other cracks anywhere else on the bumper, thankfully. And the ones I found were all really shallow, so they sanded out relatively quick. The dark shadow on the bare polyurethane is just sanding dust. If it doesn't come off when I scrub the bumper before primer, I'll be sure to sand it off to get some good paint adhesion.

The only thing left to sand is the bevels around the COBRA letters, then this bumper will be ready for primer.
 
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Chythar

Recently finished repairing my rear
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At last, the weather warmed up here in SoCal so it was time to lay primer on the Cobra bumper. Even though one can theoretically paint all the way down to 55°, I don't feel comfortable until it hits at least 70°. Which it did last Friday here. But before primer, I had a lot to do. First off, I finished sanding the bevels around the "COBRA" letters. This was the last bit of sanding left. Here's two combined photos, of before and after.

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When I tried to mask off the COBRA letters for sanding, I had some trouble. I was using 3M Precision tape (06525), and it was perfect for the straight edges. But getting the tape around the sharp curves on the letters wasn't working. Some internet research told me about vinyl tape, so I picked up a roll of 3M vinyl tape (471+, 1/8 in wide). And it worked great! Until it didn't. Seems the adhesive softens some under direct sunlight, and the tape shifted off the sharp curves inside the "B" and "R" letters. The fix was to use 3 pieces of tape instead of bending a single piece, each piece handling part of the curve. That worked. After I finished sanding the bezels, the tape was messed up so I pulled it all off and reapplied it.

Oh, did I mention I forgot to take pictures of all of this? Oops! Oh well.

Next, it was time to wash the bumper and remove all the sanding dust. It's kinda important to get the primer to stick to the bumper and not the dust - ya think? The bumper was probably covered in fingerprints and other stuff that would also make paint adhesion really tough. I have a pack of the Scotch Brite pink scrubbing pads, so I grabbed one and scrubbed the bumper down with blue Dawn dish soap. I wiped the bumper dry with a paper towel...and saw some black sanding dust on the towel. Washed the bumper again, and still had dust on a new paper towel. I must have scrubbed that bumper at least 20 times over a couple of hours before a final paper towel wipe came up clean. Not sure if I was doing something wrong, or if the residue on the paper towel was something else, but I guarantee that bumper was CLEAN. I used a toothbrush on the bare polyurethane patches, and they turned out nice and bright.

Note to self - don't wait to scrub the bumper clean until the day before you paint. I could have done most of that scrubbing days earlier.

Friday - Primer Day. The bumper was prepped and ready. It was time to put up my temporary painting booth. It had gotten pretty messed up when I left it up last fall and it rained, so I had to re-staple the plastic sheeting back up. It took an hour or so, but it all went back together real nice. I then swept out all the dirt on the floor, and wiped down all the plastic to remove any dirt or dust. Finally, the booth was clean and ready.

Brought the bumper outside on its stand, then did a final wash and rinse to get rid of any remaining fingerprints and oils. Scrubbed all the to-be-painted surfaces with a pink scrubber and blue Dawn dish soap. Rinsed off the soap with a garden hose, then rinsed the bumper again with filtered (deionized) water as I'm sure the water from the pipes isn't very clean. Finally, I let the bumper air dry. This is when the 3M vinyl tape adhesive shifted in the sunlight.

Fixed the tape, moved the bumper and its stand into the painting booth, then blew off any remaining dust with a can of compressed air. There were a lot of little spots where I over-sanded and revealed the polyurethane, not to mention the large patches where I sanded out cracks, so I just covered the whole bumper with SEM XXX Adhesion Promoter (77723). When the adhesion promoter was dry, I applied SEM Flexible Primer Surfacer (39133, in gray). Strangely enough, I used 1 1/2 cans of primer and ran out before I finished the bumper. Had to order another can of 39133 from my local auto parts store. Their primer was more expensive, but the store got it to me the next day (Saturday). And fortunately, Saturday was also forecast to be over 70°. The primer says you can sand and paint after 35-40 minutes, so the next day was just fine.

Saturday - Fix the Primer Day. Got the can of primer from the store, wiped the bumper down with a tack cloth and applied the primer. This time, I got enough paint down to completely cover the bumper - and still have most of the can left. I held the can a little closer to the bumper this time, and the primer covered well without drips. Let it all sit out overnight to cure and outgas some. Here's a photo of the bumper sitting in the painting booth on Sunday, just before I moved the bumper back inside and broke the painting booth down.

20220220_152154.jpg


Next up: gonna let the bumper sit for a week to make sure the primer has outgassed and hardened, then more sanding.
 
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Chythar

Recently finished repairing my rear
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West Los Angeles, CA
Still working on the Cobra bumper, but progress has been slow. I'm fixing one area on the bumper, but I can only do a bit of work before I have to wait a day for some epoxy to cure. When we last left off, I was letting the bumper sit for a while until the paint stopped outgassing. That took several days longer then I thought. In the meantime, I inspected the whole bumper for anything that didn't look right. The topcoat won't cover up any imperfections, so anything left in the primer will still be there after you paint and polish. Everything looked good, even the areas that had cracks in the polyurethane. Well, except for the beveled insert in the top of the bumper, and a small spot on the side where I sanded off an edge. Restoring the edge on that small spot should be easy with a layer or two of paint and some sanding, but it was the beveled insert that was a problem. I could easily see that I had widened the insert, and I couldn't simply ignore it. This is the time to fix these issues, right?

I compared some measurements from the other side of the bumper, and decided that I only needed to add material to one side of the insert. I sanded off the primer and got the area back down to polyurethane, then washed the bare polyurethane with soap & water. I added material by applying bumper Bondo - it's a 2-piece flexible epoxy that adheres to the polyurethane really well. The flexible Bondo would be completely cured by the next day, so I'd sand it down smooth with a power sander and 80-grit sheets. Finally, I measured the result to see if I had to add more flexible Bondo. For me, measuring the width of the insert was the best way to know if the insert had been fixed.

It took a while to build the flexible Bondo up, mainly 'cause I didn't put the Bondo on even enough sometimes and ended up sanding most of it off to get it smooth again. I'd spend maybe 5-10 minutes sanding the cured flexible Bondo smooth, then a few minutes more adding more flexible Bondo. Counting tool cleanup, I could only spend maybe 30 minutes a day on the bumper. The rest of the time, I was waiting for the flexible Bondo to cure. Have a combined picture; the left half with exposed yellow polyurethane shows how big of an area I had to fix. The other half shows a mostly-fixed insert - the black is the flexible Bondo.

20220310_193129.jpg


I shot a couple coats of primer over the insert yesterday, 'cause it's really hard to see the full shape of the insert when it's in black and yellow. Looks like I'm close to finished, but I need to refine the edges some more.
 
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Chythar

Recently finished repairing my rear
15 Year Member
Aug 26, 2004
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West Los Angeles, CA
WOW....my hat go off to you for persistence working on those bumpers...:fuss:

I bought my 95 in 1998 and used this site for years and I remember you posting up all the time. It's cool to see your still at it.
I remember you as well. I'm not sure if I'd call it persistence or 'too stupid to quit', but that could describe most of us. :rlaugh: Thanks for the compliment.
 
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Chythar

Recently finished repairing my rear
15 Year Member
Aug 26, 2004
2,353
134
113
51
West Los Angeles, CA
Finished fixing the bumper and sanded it all smooth. I can't see where the bumper was repaired, even if I get up close. The instructions with the top coat I'm using says to sand the primer with P400 or P600 for good adhesion; I used P600 to make sure all surface imperfections were gone. Note I said P600 and not 600 grit; the 'P' denotes it as a European standard and it is NOT the same as the US/ANSI "standard" 600 grit! P600 is closer to 400 grit. P80 to P240 is about the same as 80-240 grit, but the difference gets bigger the finer the sandpaper. 600 grit is about the same as P1000, which would be WAY too fine for the top coat to adhere. So I'm glad I looked up the difference.

If your sandpaper has any other letters before the grit number, it's still the US/ANSI standard. The letters indicate the type of material the grit is made from, and whether it's wet/dry sandpaper. For example, most of the sandpaper I have says "CW XXX" - so CW 600. The "C" represents silicon carbide, and "W" means wet/dry sandpaper.

Lesson over, pop quiz next class period. After sanding, I removed all the masking tape and scrubbed the bumper with blue Dawn soap. I'll wash the bumper again just before painting, but this wash gets rid of any sanding dust and any buildup of skin oils from touching the bumper. The discoloration off on the right is just water that hasn't evaporated off. The COBRA letters look really good!

20220403_223719.jpg


I'll be re-taping up the COBRA letters in the next few days. We're getting a heat wave here in Los Angeles this upcoming week, so it is finally time to paint the top coat on the bumper. FINALLY.
 
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