I made a mess... Any suggestions?

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PostPosted: Fri Jun 30, 2017 6:18 pm
Hey, I started repairing a badly damaged bumper from a 93 Trans Am and I think I made a bit of a mess. I'm going to list what I think I did wrong and I was hoping for some opinions on how to fix it..

1. I used lightweight Feather-rite filler to repair damage on the front of the bumper. The problem is the can of filler mentions use on metal but says nothing about plastic. After using it I found out that people use plastic filler for bumpers. The filler I used seems to have worked well and the area I used it isn't very flexible. So my question is, will it be okay? Someone had previously repaired it and it was the same brown-colored filler. I thought plastic filler was white?
2. I used rivets and aluminum plates to hold the bumper together as it was cracked stretching from the front nose all the way to underneath the bumper. There was also a piece that had fallen off. I used JB plastic weld and 3m plastic stuff to repair a lot of this but I wasn't sure if it would last in the long run, so I used the rivets to help hold it together while repairing and was thinking of leaving them for extra support as its a pretty heavy bumper. The underside of the bumper is not visible and pretty badly damaged. My thought was to simply paint the visible parts of the bumper and then maybe work something else out for the underside. Just use spray paint/undercoating? I didn't now if that would risk having the visible-paint peel though..
3. I used 80 grit to get out big scratches and spider cracks. I read someone say that that will lead to pinholes and that I need to use filler now, but Idk if that's true. I thought I sanded the area pretty well with 180 afterwards.
4. I saw people mentioning to use finishing glaze or putty after using filler but is that necessary? When I look up tutorials they don't mention using putty afterwards. I do have pinholes but I was going to use some basic 1 part bondo product for them (Bondo 907 Glazing and Spot Putty).
5. Do you know what the white stuff is in the pictures? Im guessing that would be plastic filler from a previous repair. There are some spiderweb cracks that seem to not want to come out no matter how much I sand. Should I use filler over them?
6. The Auto-Body sticky recommends the first coat of primer at 220 grit, then paint at 400-600. Does that also apply to plastic? I am also unsure whether to use sealer and/or primer?

I know its a mess, but new bumpers are super expensive and I see it a learning experience.. It's a combination of previous-owner and my own repairs. I am not trying to make it perfect, I just want something semi-presentable until I can hopefully buy a new bumper down the road. I'm painting it Black, so I guess that makes it a little bit easier. I did look at the stickied thread and google to try to find answers but I couldn't find specifics on my situation. I know this post is annoyingly long (sorry about that) but if anyone has any opinions, thanks for replying.
Attachments
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I know I went overboard here.. ^ LOL. Previous owner seems to have thrown on bondo for the repair. Never had a problem with it cracking, so I just JB welded a little over it.
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PostPosted: Sat Jul 01, 2017 4:57 pm
Toothe555 wrote:Hey, I started repairing a badly damaged bumper from a 93 Trans Am and I think I made a bit of a mess. I'm going to list what I think I did wrong and I was hoping for some opinions on how to fix it..
Okay, I'm going to throw out some answers in bold here so we can go down your list here.
1. I used lightweight Feather-rite filler to repair damage on the front of the bumper. The problem is the can of filler mentions use on metal but says nothing about plastic. After using it I found out that people use plastic filler for bumpers. The filler I used seems to have worked well and the area I used it isn't very flexible. So my question is, will it be okay? Someone had previously repaired it and it was the same brown-colored filler. I thought plastic filler was white?That would be USC filler there, right? If it is you should be okay. Fillers can literally be any color especially when adding different colored hardeners.
2. I used rivets and aluminum plates to hold the bumper together as it was cracked stretching from the front nose all the way to underneath the bumper. There was also a piece that had fallen off. I used JB plastic weld and 3m plastic stuff to repair a lot of this but I wasn't sure if it would last in the long run, so I used the rivets to help hold it together while repairing and was thinking of leaving them for extra support as its a pretty heavy bumper. The underside of the bumper is not visible and pretty badly damaged. My thought was to simply paint the visible parts of the bumper and then maybe work something else out for the underside. Just use spray paint/undercoating? I didn't now if that would risk having the visible-paint peel though.. Those old GM plastics don't age very well, and start sagging even just after a couple of years on the car. I'm not wild about the rivet idea there as tears can start at those rivets. When I see this type of damage on a large area like this I usually take two sheets of steel or aluminum and sandwich the plastic between them using bolts/washers. This stiffens the entire area but by leaving the holes for the bolts/washers a little bigger doesn't give me tear points. As for undercoating I would use catalyzed bedliner instead. Much tougher. And, not saying you can't do some incredible things with JB weld but it's better to use stuff designed for your application
3. I used 80 grit to get out big scratches and spider cracks. I read someone say that that will lead to pinholes and that I need to use filler now, but Idk if that's true. I thought I sanded the area pretty well with 180 afterwards.If you are concerned about pinholes cream those areas with USC's Poly Flex glazing putty.
4. I saw people mentioning to use finishing glaze or putty after using filler but is that necessary? When I look up tutorials they don't mention using putty afterwards. I do have pinholes but I was going to use some basic 1 part bondo product for them (Bondo 907 Glazing and Spot Putty). NEVER use a 1 part filler for anything we do on cars. That was old tech. used back in the lacquer/enamel days and it was crap back then. You want that USC Polyflex for this. Just an opinion but yes, finishing off with these higher quality glazing putties will yield a better surface.
5. Do you know what the white stuff is in the pictures? Im guessing that would be plastic filler from a previous repair. There are some spiderweb cracks that seem to not want to come out no matter how much I sand. Should I use filler over them?Yeah, that is probably old filler. If you've got spider webs you must V cut down inside them with something like a Dremel tool so they do not come back after filling. This is where the Polyflex will help again.
6. The Auto-Body sticky recommends the first coat of primer at 220 grit, then paint at 400-600. Does that also apply to plastic? I am also unsure whether to use sealer and/or primer?Yep, sticky is pretty much right on. I prefer to seal bumpers up with epoxy before moving on to primer, etc.

I know its a mess, but new bumpers are super expensive and I see it a learning experience.. It's a combination of previous-owner and my own repairs. I am not trying to make it perfect, I just want something semi-presentable until I can hopefully buy a new bumper down the road. I'm painting it Black, so I guess that makes it a little bit easier. I did look at the stickied thread and google to try to find answers but I couldn't find specifics on my situation. I know this post is annoyingly long (sorry about that) but if anyone has any opinions, thanks for replying.
Black is a great paint to match but is the worst when it comes to showing bad body work. These bumpers intensify the bad bodywork also because they are so distorted from aging. Just take your time, don't rush the sealer/primer process and make sure you guidecoat your primer.
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!

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PostPosted: Sat Jul 01, 2017 5:48 pm
Looked up your bumper at www.polyvance.com and it comes up as PUR or RIM plastic which are both thermoset plastics which can be difficult to bond. According to them the most current best way of fixing them is by using a process of "plastic brazing" which is much like regular plastic welding however the original plastic surface doesn't really melt. The urethane filler rod does melt and locks in a v groove you create for the bonding process. The more simple airless plastic welders work for this process. They also sell a good quality plastic bumper repair material specifically for repairing PUR and RIM.
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!

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PostPosted: Sun Oct 29, 2017 4:46 pm
These guys list used and new bumper covers.
https://store-yiwxi.mybigcommerce.com/c ... f02034a93c

Another source of "reconditioned"
http://bumperworksonline.com/front-bump ... -2898.html

More used
http://www.tacreationsusa.com/93-02_firebird.htm

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