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  1. #1
    FEP Power Member dagenham's Avatar
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    Default Bumper cover prep??

    This question is for Trey or Or any other pro painters.
    I'm prepping a used '85 front bumper cover for my Saleen. It has been repainted once and with clearcoat. It has a lot of cracks in the paint from what I can only guess coming from being moved around without the header panel in it and maybe from being bumped while on whatever car it was on.
    So my question is this: Should I try to sand down far enough to get past the cracked paint (if possible) or will the high build primer I shoot on it be ok, especially if I put flex additive in it and the paint and cc?
    Question 2: if it should be stripped to bare plastic, what's the best ways of doing that?
    Current Mustangs
    1966 6 cylinder coupe
    1984 SVO 9W
    1985 Saleen #132

  2. #2
    Moderator wraithracing's Avatar
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    I would recommend either stripping to the bare plastic or at least sanding all of the cracked paint down to the bare urethane. In my experience cracked paint like that on the bumper covers will come back to haunt you if you try and paint over it. The cracking is generally due to the bumper flexing more than the paint can handle and/or the paint have very little flexibility due to lack of flex agent or just the paint drying out due to age/sunlight/etc.

    Sanding can be down with coarse enough sand paper to get the job done. I generally wouldn't use anything coarser than 80 grit to prevent additional damage/repair work to the urethane underneath. You can also check with Media blasters in your area and see what it would cost to have the bumper cover media stripped.

    Once the bumper cover is sanded or stripped down then you will need to primer the affected areas and/or the whole cover and sand/smooth all the repair work. You will want to use a quality primer/high build primer that is designed for urethane. Once the cover is prepped/sanded and ready for paint, you should be able to spray with a quality base coat and clear coat without any need for additional flex agent unless recommended by your paint supplier/manufacturer. Most of the modern paints are designed for all the urethane/plastic on automobiles today and don't require additional flex agent like the paints did back in the 80's/90's.

    I do recommend one of two things in regards to the front bumper specifically. Either make sure the reinforcement is installed before painting so you don't have to flex the cover to fit over the reinforcement or make sure the front cover is really nice and warm before installing the reinforcement that will help prevent cracking the paint. Obviously with winter coming that will require some additional work if needed to heat up the cover, so just be aware.

    Oh also in regards to primer, you want enough on the cover to seal and provide a good base for your top coats, but no more than needed. The additional layers of primer/basecoat/ and clear coat will only lead to the possibility of additional cracking due to the added mil thickness of all the products. So if spraying a high build primer to smooth out imperfections, etc. you want to make sure and build up only the areas that need the high build rather than the entire cover unless you just want to do a lot of extra sanding. Your base coat spray out should be 2-3 coats only, once you have full even color coverage there's no need for additional coats. If spraying a color like red or others that sometimes don't cover well, then consider either a light color primer/sealer that improves the base coverage or again a seal coat tinted to a similar shade as the base coat. Finally depending on your brand of clear coat the same holds true in regards to generally 2-3 coats of clear. Hope that helps and I am sure Dave will give you some additional thoughts and advice.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  3. #3
    FEP Power Member dagenham's Avatar
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    Thanks Trey. I appreciate the advice.
    Current Mustangs
    1966 6 cylinder coupe
    1984 SVO 9W
    1985 Saleen #132

  4. #4
    FEP Member Hans's Avatar
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    Can I ask your advice on repairing cracks in these covers?
    My latest purchased cover (cobra, with the extensions), are cracked at both sides due unsupported storage in a pile of parts.

    Where to find info on repair materials and tips?
    Thanks,
    Hans.

    Verstuurd vanaf mijn ALE-L21 met Tapatalk

  5. #5
    FEP Senior Member droopie85gt's Avatar
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    Default

    I think some people have used panel bonding material and some drywall patch mesh. I think @davedacarpainter did it.
    1985 GT, Sunroof, 5 Lug, Rear Discs, 01 Graphite Bullets, 88 forged piston shortblock, 2.02/1.60 Alum heads, Weiand Stealth, Holley C950 TBI, BBK Long tubes

  6. #6
    FEP Power Member STL79Coupe's Avatar
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    As Trey mentioned the media blasting make sure the company knows what they're doing. I had a rear cover soda blasted and it pitted it really bad. It was almost like tearing the top layer of a sponge off in pieces. This was 8 years ago so maybe the process or technology has been improved.
    Keith formerly STLPONDS
    '79 V8 coupe in the works!
    Build thread http://vb.foureyedpride.com/showthread.php?t=89153

  7. #7
    FEP Power Member dagenham's Avatar
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    I've used soda blasting material in the past. Works very nice. Maybe a bit of experimenting is in order. I have a sand blaster. You have to turn the material flow rate way down because of the fineness of the baking soda vs the sand.
    Current Mustangs
    1966 6 cylinder coupe
    1984 SVO 9W
    1985 Saleen #132

  8. #8
    FEP Power Member STL79Coupe's Avatar
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    I don't know exactly what happened, but the guy had a full blown SB rig operation that he did car bodies etc. It might have been the urethane on the bumper or to much pressure. I just try to let people know to be careful with this bumper covers since they're getting harder and harder to find in good shape. GL with you project.
    Keith formerly STLPONDS
    '79 V8 coupe in the works!
    Build thread http://vb.foureyedpride.com/showthread.php?t=89153

  9. #9
    Moderator wraithracing's Avatar
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    Quote Originally Posted by Hans View Post
    Can I ask your advice on repairing cracks in these covers?
    My latest purchased cover (cobra, with the extensions), are cracked at both sides due unsupported storage in a pile of parts.

    Where to find info on repair materials and tips?
    Thanks,
    Hans.

    Verstuurd vanaf mijn ALE-L21 met Tapatalk
    I am not sure what is available in your area. I personally have been using the Lord Fusor line of urethane adhesives and urethane repair products. They offer several options depending on exactly what you need to do. I just used some of their products to repair a 1985 and 1986 front cover. I was able to patch a couple of tears on the backside and then fill and finish the cover on the front side.

    I also use Evercoat Polyflex to do final finesse work on imperfections on the front covers too.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  10. #10
    Moderator wraithracing's Avatar
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    Quote Originally Posted by STL79Coupe View Post
    As Trey mentioned the media blasting make sure the company knows what they're doing. I had a rear cover soda blasted and it pitted it really bad. It was almost like tearing the top layer of a sponge off in pieces. This was 8 years ago so maybe the process or technology has been improved.
    Some of these covers, especially the early Four Eyed versions can be very soft or brittle due to age, UV exposure, and the urethane used back then. As the you move up thru the model years, the covers get a bit better, but still much different than what is used on new Mustangs today. I have seen some covers that have urethane so thin in some areas you can actually see thru it. The only option in that case, is to be extra careful and then use products like Lord Fusor, 3M, Dura-Mix, etc. to patch and build up the weak areas. Then either Polyflex and/or high build primer to smooth out the imperfections to make it look new again.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

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