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  1. #1

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    Repairing and repainting small amounts of rust in engine bay

    I`ve got a 17 year old car that`s not worth the amount of money I spent to modify it. I recently noticed rust underneath the strut tower brace and I`m looking for a way to properly fix this. There are a couple of other small areas that could use some preventative maintenance, as well. I`ve seen products online that you spray on the rust that turns it black, but my engine bay is really clean, so that`s not an option. Do I just grind this down with a Dremel, then apply touch up paint? I want to make sure it doesn`t come back. If necessary, I`ll go to the body shop, but I don`t know how much money they`d charge me, even though it seems like a minor job. The driver side looks worse than the passenger, but I want to prevent the passenger side from getting worse. Please let me know what you think.

  2. #2
    Migue's Avatar
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    Re: Repairing and repainting small amounts of rust in engine bay

    You could:

    Clean threads with a wire brush to remove some if not all the rust from them and then the base around the studs you can hand sand(if using a dremel be careful as to not over do it nor damage the threads) with 80-120 grit to knock the rust out and if that works(if it doesn`t,try a heavier grit like #40) then increase grit to 220/400/600(you can go gradual or you can just try going straight to 400 or 600 since it`s under the hood and we`re not looking at a flawless job/result here) to prep for your primer/touch up. It`s not going to blend in all professionally,especially since it looks like you have flakes/pearl in that paint but at least it`ll look more presentable.

    Prep is key so make sure that before you apply your touch up(maybe even look into a primer that can help prevent rust before you apply touch up), everything has been thoroughly wiped down with a wax and grease remover and wear nitrile gloves to prevent your skin oils touching that area. This should help provide a semi-permanent or more durable solution and buy you time. I wouldn`t use heavy grit paper on the areas that are just chipped without rust, i would spot sand those gently with 600 or finer to promote bonding of the touch up. Save the aggressive stuff for the rust and try not to sand the paint off everything in that area, keep it controlled to the true problem sections only which according to your picture, are the immediate areas surrounding the studs only.
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    XxBoostinxX's Avatar
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    Re: Repairing and repainting small amounts of rust in engine bay

    Before getting aggressive.... I would try some of Locktite`s Naval Jelly (http://www.lowes.com/pd/LOCTITE-16-o...8-36df8d306658). It is cheap and it works well.
    2006 Saleen S281 Supercharged - Black

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  4. #4
    dansautodetailing.com Stokdgs's Avatar
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    Re: Repairing and repainting small amounts of rust in engine bay

    Great advise above !!! ^^^^^^^^^^^^^^^^

    Lastly, try to determine where the moisture that caused the rust is coming from - the top and/or from underneath..
    That way you can be sure to get all the rust out and it won`t come back..

    I forgot about all those naval jellies that were so popular in the 80`s on ... They did work well too..

    At the paint shop we used to rub a 3M acid based liquid product on all bare, sanded, metals that kept them from rusting while waiting to get primed, painted, etc..

    It would be considered an extra step to do this, but it is worth it to keep the metal perfectly rust free before you start the primer and paint process..

    On all aluminum metal we used a zinc-chromate yellow primer that was made for aluminum and that always worked great..
    Dan F
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  5. #5

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    Re: Repairing and repainting small amounts of rust in engine bay

    Agree the key to the fix is prep. I have used Corroseal Primer on this kind of a repair. It is a rust converter type product that is also a primer. Their website explains it better than I can, but it goes on by brush. It is white when applied and turns black on the rusty parts. It dries clear on non rust part (the painted bits). Wait 24 hrs and then paint over the primer same as normal. Nice thing is even brushed on leaves nice finish (you can of course spray over for even better finish).
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    Migue's Avatar
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    Re: Repairing and repainting small amounts of rust in engine bay

    Quote Originally Posted by CrispyGP2001 View Post
    Agree the key to the fix is prep. I have used Corroseal Primer on this kind of a repair. It is a rust converter type product that is also a primer. Their website explains it better than I can, but it goes on by brush. It is white when applied and turns black on the rusty parts. It dries clear on non rust part (the painted bits). Wait 24 hrs and then paint over the primer same as normal. Nice thing is even brushed on leaves nice finish (you can of course spray over for even better finish).
    Cool thanks for the info and confirmation that it works. I am actually in the process of doing what I can to remove/stop some minor rust on my beater car....but it`s at the edge where the roof meets the windshield gasket,thankfully there`s a bit of a gap that allows me to get in there a bit. I`m just giving it a vinegar treatment(applying precise drops to affected area every few hrs.)for now to loosen up the rust before I get in there with a brush and sand paper and then I was planning on using the corroseal ,just wasn`t sure if it was worth it .
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  7. #7

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    Re: Repairing and repainting small amounts of rust in engine bay

    Great replies, thank you! I was leaning towards brushing and sanding, then some touch up painting, but Corroseal sounds like a great product. There are so many rust converter products out there. Is this considered the best? Should I brush and lightly sand, then apply Corroseal or just skip the sanding?

    Stokdgs, as you mentioned, I`m concerned that it might be coming from underneath, but I didn`t see anything that jumped out at me when I looked. All I could see was factory coating.

  8. #8

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    Re: Repairing and repainting small amounts of rust in engine bay

    The sanding will yeild a smoother finish. The thicker the rust the more bumpy the surface. If you get it all off then the Corroseal will act like a normal primer (no colour change). There is a limit on how far the Corroseal can penetrate. If it doesn`t convert it, will come off just like paint does, if just put it over a rust spot. Their website is a good source for more info.
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  9. #9

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    Re: Repairing and repainting small amounts of rust in engine bay

    Quote Originally Posted by CrispyGP2001 View Post
    The sanding will yeild a smoother finish. The thicker the rust the more bumpy the surface. If you get it all off then the Corroseal will act like a normal primer (no colour change). There is a limit on how far the Corroseal can penetrate. If it doesn`t convert it, will come off just like paint does, if just put it over a rust spot. Their website is a good source for more info.
    Thanks man, I appreciate the help and recommendation. I called Corroseal today to see if it would damage surrounding paint and was told that it wouldn`t. They offered to send me a small sample. One more question, would you tape off the threads or treat them, as well?

  10. #10

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    Re: Repairing and repainting small amounts of rust in engine bay

    I would not treat the threads. The Corroseal will add thickness to the threads making them hard to re-assemble and likely come off on re-assembly. After it is assembled could use it to "seal" the exposed bolt. I would just hit the threads with a small wire brush and WD40. If you really want to get fancey Loews has plastic/rubber caps you put over the exposed threads, thereby sealing them.
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  11. #11

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    Re: Repairing and repainting small amounts of rust in engine bay

    I`m currently doing this kind of work on the Crown Vic`s undercarriage and I`ve done it before on numerous vehicles. Few approaches have worked long-term, *no* approaches have always worked 100% every single time (but some do work almost every time and I do mean long-term).

    Hope the CorroSeal works, never tried it. Make sure it gets everywhere it needs to get.

    Q: If you treat with CorroSeal, what needs to be done after that? Will it do much if left untopped? IME if you convert rust and then leave it like that the rust comes back. The rust extends beyond what you can see/treat topically and that can cause future issues.

    Q: Does this area show? Do you want to end up with metallic blue paint there or is a satin-black finish OK?

    Q: Can you get to both sides?

    Q: Can you disassemble it, get the threaded parts out?

    (I`d just about bet my life that the rust is on both sides of that and is creeping through the gaps/seams around the threaded bits. You need to treat the rust in areas you can`t really get to directly in order to to treat the rust then seal it up with the right stuff.)

    IMO you need to get something between the various parts involved, something that`ll seep into the gaps/seams and get to everywhere that`s corroding and neutralize/arrest/seal the rust- those "oblong pieces that the threaded bits stick up through" that`re outlined with rust are a clue that the whole area is rusting on both sides. Then you need to seal the whole area (extending out a ways from where you can see the rust) with something that`ll keep the residual rust from spreading (something like, but better than, POR15). Yeah, there *will* be residual rust unless you can disassemble/strip back a few inches to bare metal/work from there.

    Potential big problem- if that area flexes any then whatever product bridges the seams will probably crack, opening a new gap where new rust can start/old rust can spread.

    IME Rust Converters seldom work well for repairs like this (good for other jobs though). I do much better when I treat the rust with an acid-based product that leaves a Zinc coating behind (current fave: RustBullet Metal Blast) and then prime with KBS RustSeal (not POR15, and not RustBullet either although that`s worked OK too in some cases but not ones like this). And then use a creeping/seeping rust preventing product to further keep moisture out.

    If the area doesn`t show I`d go about it differently (and probably more effectively) with stuff that`s not paint-friendly (the "satin-black product look" approach).

    I just don`t see conventional "abrade/treat/prime/paint" methods working long term for this one, *GOTTA* get the right product on all the corrosion and then seal it up from air/moisture because you won`t get it *all*.

    So if that were mine I would:

    -figure out how to get to both sides of the area in question
    -treat it with Metal Blast (and it`ll take a long dwell time, not just minutes- saturate paper towel figure out a way to hold that in place)
    -Prime with numerous coats of RustSeal, again on both sides/everywhere and going beyond the obviously rusted area
    -Topcoat with touchup paint (and then let it dry for a while)
    -Rustproof with something that`ll creep into the gaps/etc. (something good, not WD40- check out ACF-50, that`s what they use for this on riveted aircraft panels or the black version of Eastwood`s Frame Coater stuff) to further slow down a return of the rust. If that stuff showed I`d live with it (better than rust IMO).

    Speaking of "if that were mine", this isn`t all that different from some stuff on the Crown Vic (e.g., front stabilizer bar mounts). But in my case "satin black" is an OK look so I have it much easier. IF I had that *exact* problem and wanted to really fix it, I`d have the struts out to do the work. Yeah...I know..but that`s what I`d do.

    Sorry this is just a [crappy] poorly presented rambling response..reads that way to me but it`s a tricky thing to convey (and a tricky thing to do successfully!). Also sorry for the "buy these different products you`ve never heard of" aspect of it..I have a ton of Rust Remediation/Prevention products that have *not* worked well for me and I`m not trying to waste anybody`s time/money on something where success is always iffy at best :0
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  12. #12

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    Re: Repairing and repainting small amounts of rust in engine bay

    Oh, for the threads...I`d neutralize the rust on them first.

    Then probably treat with the Eastwood BHDAR..that`ll leave a "black painted threads look" but you can clean it off later with solvent if you need to and then reapply. Or try to *lightly* paint them with the "Galvanized steel color" KBS Rust Seal. Or treat them with something like Amsoil`s Heavy Duty Metal Preserver or the ACR-50 (those will need touched up now and then and might attract/retain a littel dirt). Haven`t decided what I`m gonna use...probably the BHDAR since I don`t mind black threads and it`ll stay tidy.
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  13. #13

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    Re: Repairing and repainting small amounts of rust in engine bay

    Quote Originally Posted by CrispyGP2001 View Post
    I would not treat the threads. The Corroseal will add thickness to the threads making them hard to re-assemble and likely come off on re-assembly. After it is assembled could use it to "seal" the exposed bolt. I would just hit the threads with a small wire brush and WD40. If you really want to get fancey Loews has plastic/rubber caps you put over the exposed threads, thereby sealing them.
    That`s what I was thinking. It might add too much thickness and I`d have to get a tap to remove the stuff. It`s not a big deal, so I`ll just leave it.

    Quote Originally Posted by Accumulator View Post
    (I`d just about bet my life that the rust is on both sides of that and is creeping through the gaps/seams around the threaded bits. You need to treat the rust in areas you can`t really get to directly in order to to treat the rust then seal it up with the right stuff.)
    I was feeling pretty good about my little project until I read your post. From the very beginning, I was concerned that this was something that could be coming from underneath. If I don`t stop it now, it could spread to the point where I`d need someone to do some welding. I posted this on a car forum, and the only response was "I believe alot of people would love to have that little rust. That is just minimal surface rust, so just lightly clean it up with a wire brush and then put some rust converter on it to seal the area." At this point, it might be a good idea to talk to a body shop. If it`s just on the surface, I`ll do it myself, but if the undercoating needs to be removed to repair a rusty area underneath, I don`t have the garage space to handle a project like that.

    By the way, here is a picture of the passenger side. In both pictures, the square area surrounding the studs has some paint missing, because the metal plate attached to the strut tower brace scraped it away. All that will be hidden, but I still want it painted blue in the end. Look in the background and you can see some rust in the seam near the strut bolt.
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  14. #14
    dansautodetailing.com Stokdgs's Avatar
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    Re: Repairing and repainting small amounts of rust in engine bay

    Quote Originally Posted by jwyfk View Post
    Great replies, thank you! I was leaning towards brushing and sanding, then some touch up painting, but Corroseal sounds like a great product. There are so many rust converter products out there. Is this considered the best? Should I brush and lightly sand, then apply Corroseal or just skip the sanding?

    Stokdgs, as you mentioned, I`m concerned that it might be coming from underneath, but I didn`t see anything that jumped out at me when I looked. All I could see was factory coating.
    Jwyfk -
    Well, hopefully you are ok underneath, but it would always be good to look under there just to be sure...
    If the idea is to get rid of it forever there, then it may be a little more work than just cleaning it up and moving on..
    But certainly, that approach would work fine - we just don`t know how long it would last..

    What you must absolutely do to insure that your bare metal parts don`t rust up again, is get them all treated with an acid based liquid that will seal up the metal, so that microscopic rust wont start in on them again before you prime, seal, and paint it..

    And even then know that Primer does not prevent rust from starting over underneath.. It is not a sealer, it is a primer...
    Have you noticed the top side being wet all the time from rain, etc.. ??

    Like anything else, it is always good to know the root cause of the problem if possible, so you can take steps to prevent that from happening again if that is also possible..
    Good Luck !
    Dan F

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    Re: Repairing and repainting small amounts of rust in engine bay

    There`s a bearing_plate that sits between the strut tower brace and the strut itself. Maybe, you could replace those, the struts and address things with sandpaper and a sealant.

 

 
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