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Well, I did it now. I bought a coupe that had new 1/4's and I am getting it ready for paint. Well, I decided since I was going to prime the rest of the car, I should just as well take off the primer on the 1/4's and reprime that too (you never know what the PO used for paint). So I did it, I used paint stripper!! The body filler under the primer got soft and started to lift in a few spots. I scraped off what came off easily and sanded down the rest pretty good with 80.

Do I need to completely get rid of this filler or can I sand down to a point and refill over top? It is a little soft and I can dent it with my finger nail? Anybody have experience with this?

Thanks for the help,
 

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I did the same thing years ago myself on another car. I went and got rid of the affected filler and started over, but you may sand enough away that the rest may still be in good shape, It's worth trying IMHO.
 

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Based on what I've learned while working on my fastback, if the filler is soft, get rid of it. Sand it off and put fresh on it that will harden. Sand the new filler to smooth it, then continue with your primer, etc.
 
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yes remove all filler you now have moister in old filler and if there is bare metal behind it it will start to rust and you know what that means
 

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The stripper will soften filler as you stated. As you remove the soft stuff, inspect the metal surface underneath to make sure the filler was applied to bare metal, and not to a primered surface. You can tell that easily. If the original filler was applied properly and the adjacent areas are hard from no contact with the stripper, you can fill in that spot after removing the soft filler. I've done that before. No doofus on your part.
 

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HELP. You just put an uh oh in my plans. Are you saying to apply the body filler over bare metal and not a good quality epoxy self-etching primer? I thought I was supposed to prime the car before putting on the body filler, then epoxy prime it again as a sealer over the body putty, then go wtih the primer surfacer before laying down the base coat. I am supposed to paint on Saturday, so your input would be GREATLY appreciated prior to then. You may be saving me from a big mistake.
 

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If you do end up removing all of the old filler, I suggest using all metal or its equivalent instead of the plastic body filler. This is an epoxy based product with aluminum powder in it. Unlike plastic filler, it resists water. It also does not shrink or crack. I used on on my rear quarter, then back the car into the corner of the house and crunched the quarter panel. The all metal twisted right along with the sheet metal. When I pounded the quarter back into the shape, the all metal went back into shape along with the sheet metal. Did not even crack. The downside is that it will not give you a super smooth finished surface. No problem though. Just skim coat with the polyester skim filler made for that purpose. Comes out great. good luck.
 
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I have seen body filler applied over bare metal before not a wise choose though i have always been told to self etch primer before body filler. regular paint primer is a no no on bare metal because it is meant to absorb moister so that when you spray paint it is absorbed in \to the primer so it has something to stick to. Self etching primer needs to be sprayed with regular primer just within about an hour afterspraying selfetching primer or you have to sand the self etching primer so that the primer will stick to the self etching primer. Self etching primer makes to smooth of a surface when dried completely thats why the need for spraying primer while still not quite dried this allows tthe primer to melt into the self etching primer .ALWAYS check with the paint experts to make sure of compatability of diferent paint amd primers. Just some rools i follow. Just my .02 cents as some would say. And also why would you what to gamble that the old primer is ok. then have the nice paint job you spent time and money on bubble-up in 6 months over the old filler
 

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Paint stripper applied over body filler will cause the filler to soften and LIFT from the metal. Be sure to remove all old filler and reapply.
I have applied body filler over bare metal without any problems. I'm not sure of the consequences of doing so over different types of primers.

Scott
 
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As mentioned, remove all the filler down to bare metal first. If the bodywork was done properly and the affected areas were worked into shape with hammer and dolly or pulled properly there should only be a light coat of filler smoothing the worked surface. Filler is best applied directly to the metal after it has been DA'ed with 36 grit paper to provide a nice rough surface with enough tooth for the filler to adhere properly. Filler can be applied over most epoxy primers but the metal beneath that is to be covered by filler should be a rough surface for proper adhesion of filler. The filler is then worked and reapplied as necessary to provide the proper contour. After that, it is just a matter of priming and blocking and priming and blocking with recommended grits of sandpaper using guide coat to find low spots until the surface is perfect and ready for paint.
 
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