Monday, August 30, 2010

Side-strip delete and HTS-2000 for filling holes

I had mentioned earlier that I pulled off the small rubber strips that run along the side of the car, commonly called side strips or door bumpers. The metal rail holding the rubber strips was held on with several rivets, and when I removed the rail, I was left with 10 holes on each side of the car. I purchased some special aluminum repair stuff called HTS-2000, which you can see more about here. They also have a pretty impressive video here of the stuff in action, which sold me. I even practiced a few times on an aluminum can just like in the video and it helped me feel more comfortable.

I bought two small rods of the HTS that are about the size of un-cooked spaghetti noodles. I started the process by cleaning the area around the holes about the size of a quarter.

I just used my Triangle Scraper, but you could also use sandpaper or a file to remove excess oxidation. I also used a drill bit to widen the hole a bit so the edges of the hole would be clean. In the pic it looks kind of black, but the metal has been scraped until shiny and clean:

Next, you’ve got to heat up the sheet-metal of the car. You've got to heat the metal enough to melt the HTS stick, but not too much that the metal warps. I used a small propane torch and just held it up to the hole, moving it around to heat up the area uniformly. It only took about 15 seconds for the metal to heat up. That’s about when smoke started coming out of the back of the panel. I freaked out, grabbed some water to douse flames, but wouldn’t have been able to get any water to the inside of the panel, so I just sat there and panicked. The smoke stopped and I had a chance to evaluate. There is undercoating on the back of the panel, which is really thick on the front and rear fenders, that starts to melt and burn as the panel is heated. The flame goes through the hole in the sheet-metal, and there is fire and melting paint. I ended up using a spare drill-bit and stuck it in the hole as I heated the panel, minimizing heat to the backside. There was still a little bit of stink, but it wasn’t bad.

As the panel heats up, you have to rub the HTS rod all over the area to be repaired, and as soon as the metal starts to melt the HTS, you have to pull out the drill-bit (don’t burn your fingers) and then while still heating the panel, melt the HTS into the hole just like soldering.

I laid on quite an excessive amount on the first bunch of holes until I got the hang of it. The later holes I left almost flush. I went right around the car, and welded up all the holes until they were all full.

I went back after the panels had slowly cooled and checked my welds by pushing and banging on the panels a bit. Several of the plugs loosened in the hole but didn’t fall out. Others fell out right away. I went back around and did a bunch of re-dos. Then I tested again and had two fail. More re-dos. Then I tested again and had one hole that took a few extra tries to get just right. There is so little surface area for the metal to bond to. I realized retrospectively a better way to do it.

Take a small hammer (ball peen if you have one), and gently tap right at the empty hole in the sheet-metal, making a small dimple or depression right at the hole. This way, when you weld on the HTS, there is a pea or dime sized area that stays after cleanup. Kind of like metal-bondo for the dent you made.

I thought about going back and doing this for all the holes, but was already concerned about how much heat I’d already put on the panels. I’m sure that I’ve had some metal distortion, and can see some minor waviness in the panels that I’m hoping the filler primer will cover up. In retrospect, I’m happy with what I did, but imagine there might be some other product out there that would do a similar job, but without the heat to the panels risking fire, and messing up my nice straight panels. You could maybe even get away with denting in the hole and then filling it with actual Bondo, but I think there’s too much risk there of it causing problems later on down the road.

Once that was done, I spent some time sanding and grinding down a few spots where the paint had failed and the car had started to have some minor surface rust.

Total time spent today: 2 hours
(I won’t count the cost of the rods here since I added them in earlier, they were $2.50 on ebay)

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