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  1. #1

    Default Undercoat Removal/Re-Coat?

    So my paint and body guy came to look at the car prior to paint and he said if I wanted the engine bay done properly I would have to get rid of the undercoat that has been haphazardly sprayed all over. Fast forward through the weekend (I spent the whole weekend trying to get it off and most of it is gone but not all). I accomplished all this with a combo of professional strength goo-gone, scrapers, screwdrivers, a power-washer (my idea of soaking it in goo-gone and blasting it did not work btw).

    Long story short the engine bay is mostly cleaned up and will probably require scotch brite and hours of scrubbing to get the little bits off.

    Now to get to my question: Is it worth stripping the bottom of the car? The undercoat appears to still be in-tact and there is little to no rust. I will need to remove it in some spots to weld in the subframe connectors and treat the very limited amount of rust down there but is it really worth it to go through hours of labor (I broke down and bought a pneumatic chisel) to remove something that has apparently protected this car from rust pretty well for the past 33 years or should I just clean it real good, treat the small problem areas and spray a light coat back over it? I really just want this thing to last and am more-so worried about preventing rust than making it look perfect.

    Also what is the best stuff to use for undercoat? I was going to treat the rust spots with a wire-wheel and por15 and then coat with *suggestions here* (3m professional undercoat?)
    1997 Mustang Cobra - Very First Car
    1985 Mustang GT - RestoMod Work in Progress
    2006 F-150 FX4 - Tow Vehicle

  2. #2

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    well assuming you are confident that the undercarriage is good (look under the carpet if you have not already). I would just take a flapper disc to any bad areas. Then treat it and hit it with some lizard skin or similar under coat. I would stay away from the por15 as that is usually applied over rust. Just my 2c

  3. #3

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    Yea the whole thing is stripped and the carpet is out (mild surface rust in small areas) the only thing left on the car are some misc brake lines that I plan to remove and the front k-member/rear end so it can roll around. I crawled under it last night an aside from being dirty and surface rust in the areas where the brake line brackets/misc brackets attach the coating is still 100% in tact save two large rust spots at the front of the floor pans. The rust in the areas of the floor pans is like a 4x4" area on both the passenger and driver side where the metal is buckled/rusted and def needs to be cut out and patched (I guess this is a common rust area?).
    1997 Mustang Cobra - Very First Car
    1985 Mustang GT - RestoMod Work in Progress
    2006 F-150 FX4 - Tow Vehicle

  4. #4

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    well I had that problem up front as well. I just cut them out and welded some fabbed panels in. just make sure you cut out enough to where you have good metal to weld to. if the rest looks good I would leave it unless it is going to be a show car or you can actually turn the body/frame and work on it that way.

  5. #5

    Default

    I’d leave it alone, the undercoating won’t hurt anything.

    I find a wire wheel works best for removing undercoat. Slower speed is better since it doesn’t heat up.



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  6. #6

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    Not all undercoatings are the same and some are easier to remove than others. I have used Tar and Bug remover (spray can) as well as kerosene. While kerosene is more dangerous to use (flammable), it works really well.
    86 SVO 2R Comp Prep
    86 SVO 9L Comp Prep
    86 SVO 7B Comp Prep

  7. #7

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    Wonder how easy-off oven cleaner would work?

  8. #8
    FEP Power Member Broncojunkie's Avatar
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    I used a wire cup brush in a drill and it stripped it right off. Hit the bare metal with some etching primer (after a thorough washing down with brake cleaner) and move on.

  9. #9
    FEP Power Member Broncojunkie's Avatar
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    As for underneath, my pace car has the original undercoating on it. There was only 1 noticeable rust spot on the vertical section below the driver's side rear seat. It looked like they missed the spot during the original undercoating. It was just light surface rust. I hit it with a wire brush to knock off the loose stuff. Cleaned with brake cleaner and coated with rust converter. I top coated with some basic black rustoleum. There are better options, but this car will only see dry weather. The original undercoating appears to have done the job and for the most part, is still holding up fine. When I install the subframe connectors, I'll do as you said. Clean off the spots for welding and then coat everything with primer and more undercoating.

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