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Under-body cleanup and piant

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David_Doan

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My car is currently mostly disassembled and I'm cleaning the underside to prep for paining. My current plan is to paint any areas that have rusted with POR15, then paint most of the bottom with truck-bed-liner.

There are some areas that clearly had some undercoating from the factory. In the places where it is stuck, it is very hard to completely remove. Is it OK to leave it and paint over it with bed liner, or take it down to bare metal and then use POR15 and/or bed-liner?

Thanks,

David
 
David, are you talking paint or rubberized undercoat? If rubberized, take it off - moisture can get held underneath. If paint take it off if possible. Your top coat will only be as good as your base - but, if it's stuck on tight it is likely to stay stuck on tight and we're talking the bottom not the top.
 
Rubberized I guess, it is sticky. I'm using an angle grinder with a wire-cup. I'm assuming anything that does not come off with that is permanent.

What about the seams in the engine bay? Clean away all the seam sealer or pain over it?
 
Personally I'm not keen on painting over rust. The idea of then going over the top of that coating with bed liner is, to me, doubling down on a bad plan. It depends the bed liner and the thickness of the POR15, but I think it violates the concept of "fat over lean", among other things. I also believe that the only factory applied undercoating is confined to the wheel arch areas. Any other under-coating is something someone else did. I'd get after it with a torch/scraper then wheel/brush. That's my .02.
 
Thanks JP & Steve, My intent is clean/prep the rusty areas then paint them with POR15. Torch is a good idea for getting the rest of the undercoating off. Should I do the same fore the seam sealer in the engine bay?


The intent of the bed-liner is in lieu of body colored paint in the wheel arches and under the car. I know these areas were originally the same color as the body, but I prefer them to be black.
 
Seam sealer is there to seal seams. Why would you want to take it off ? If you are fanatical enough to remove it to see if there is rust underneath than do so . However when you are done looking please reseal with new seam sealer before any other step. Bob
 
David,
I feel like you'd get more definitive answers if you posted pics... Are you doing all the painting and if so what are you using? knowing that would help inform the prep plan.
 
David for best results using POR-15 it’s best to have at least an 80 grit scuff for the POR-15 to adhere to, otherwise it will flake off. I chose to remove all my seam seals before media blasting with a propane torch. After that everything was thoroughly clean with gasoline then media blasted, then 80 grit scuff. POR-15 was then applied and allowed to thoroughly harden. Then a lightly scuff with 3m scotch bright and then everything was epoxy primed
then 3m seam sealed.

View attachment 25000
 
Re: Under-body cleanup and paint

AN5Sprite said:
David,
I feel like you'd get more definitive answers if you posted pics... Are you doing all the painting and if so what are you using? knowing that would help inform the prep plan.
Click to expand...

OK, this pic shows it well. Everything that is black around the seams in the engine bay and the wheel wells is some kind of tar-like sticky coating. My intention is not a bare metal frame-off, I just wanted to knock off the loose stuff 1st. I assume it is OK to paint over the seam sealer (or whatever the black stuff is) since that's what the factory did, but it feels wrong, especially if I'm going to use POR15. Any parts showing rust I want to take down to bare metal and apply POR15, but some of those areas are adjacent to the "sealer".

DSC_9601-001.jpg

My current painting plan is POR15 and truck-bed-liner for the under carriage and wheel-wells, and rustoleum for the body and engine bay.
 
BlueMax said:
David for best results using POR-15 it’s best to have at least an 80 grit scuff for the POR-15 to adhere to, otherwise it will flake off. I chose to remove all my seam seals before media blasting with a propane torch. After that everything was thoroughly clean with gasoline then media blasted, then 80 grit scuff. POR-15 was then applied and allowed to thoroughly harden. Then a lightly scuff with 3m scotch bright and then everything was epoxy primed
then 3m seam sealed.

View attachment 25000
Click to expand...

So clean to bare metal, then POR15, then primer, then sealer. You can paint directly over the sealer?
 
David,
I truly believe you'd be better off skipping the POR15 part of your plan.

Other than that, the best advice I can think to give: Whatever paint you're going to use, go straight to the manufacturer's tech department and ask them what you should and should not use under and over their coating.

Don't trust internet forums for painting advice. Thats the one thing I've taken away from most of the painting discussions I've read here and elsewhere.
 
Re: Under-body cleanup and paint

David
That is all OEM sealer and was painted over at the factory. I removed mine with mineral spirits. I used POR and primer.We are about to paint the under carriage with tinted RaptorLiner. I will use interlux brightside polyurethane to tint the bed liner and paint the car. Should be done in a few weeks. Take a look on the net. This paint will surprise you.
Paul
 
David, Actually I did a double seam seal. The first part was the POR-15 which you saw in the first photo (all the black lines you see is POR-15). I then scuff the POR-15 with 3M Scotch Brite for the epoxy primer which was applied over the POR-15. I then lightly scuff the areas that were to be seal and applied 3M Fast’n Firm 08505 beige seam sealers. This product is very flexible but has incredible bonding strength. It very toxic, a respirator needs to be used while you apply it. You can use dampen lacquered clean cloth to clean the areas where too much material was applied. This product allows you to paint over it which I will be applying a high build primer and single stage color coat. Single stage color will be applied to engine compartment, bottom of car, and interior. A base coat clear will be applied to exterior. As far of your situation not being able to see your overall situation it would be hard to advise you. In my situation I chose to thoroughly give it the longest potential preservation with the current products of today.



View attachment 25004
 
I have to amend my original reply to this thread. I was in favor of leaving the existing seam sealer in place. After seeing your pic it would be better to remove the old sealer anywhere there is a threat that rust has crept up to or into that area. Sealer is "strong" but rust is "stronger" and more invasive. Do not overlook any area where rust MIGHT be hiding. Better to search needlessly than not to search. Bob
 
Re: Under-body cleanup and paint

Blue Max,

Do you have pics of your rotisserie setup by any chance. It looks very well done.

BTW - Harbor Freight has engine stands currently on sale for $49.95.
 
Re: Under-body cleanup and paint

Thanks for all the tips and advice. I keep my blog (in my sig below) up-to-date as I work on the car for those that would like to follow. I'm sure I will have more questions that I will post here as well.

Last spring my son and I rebuilt the engine, clutch, and diff in his 1998 Camaro. There are forums dedicated to those cars too, but the audience is mostly teenagers. I really enjoy the people and community here on BCF.

Thanks,

David
 
Thanks Blue Max. Looks like a great setup. Anchored to the spriong mounting points and the bumper irons up front. I like not attaching to sheet metal as I've seen other rotisseries do. As long as you aren't replacing a bulkhead or trunk floor...Andthen I'm sure you can find other suitable anchor points for the rotisserie.
 
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