Pretty much everything is out of the engine bay but the engine on my 68 wagon. Everything that's left is begging for some sort of wash/paint/light rust coverage. The problem is, someday the whole front is coming off the car and I'll paint it properly (really, I will) and I don't want to do something that's a pain to undo in the future, like a bad POR15 job. What are my options?
Rustoleum. Get it in the can, thin it out with mineral spirits and brush it on. Or you can just spray bomb it.
When you're ready to paint for real, scuff it and paint away.
Plasti-dip if it's just for looks.
It's for basic protection of the metal for the next half decade or so. Maybe not that long. I love plasti-dip as much as the next guy, but it seems like the engine bay is the wrong place for it. Of course, it does work on wheels........
The rustoleum idea sound good. I'm cleaning right now. There's lots of cleaning to do. Lots.
Paint as little as you can get away with now...painting the engine bay a little at a time never looks right in the near or long term. Where you do have to paint, try to mask well and have a logical reason for where you start and stop the new paint.
You may recall my Opel Kadett engine bay restoration:
http://grassrootsmotorsports.com/forum/build-projects-and-project-cars/1972-opel-kadett-wagon/57132/page2/
A REALLY thorough scrub with hot water+simple green, scrub brushes, soap, rags, etc. got most of the grime, but there was still a lot of surface rust. Some mild scotch brite and WD40 was used to scrub away the surface rust the best I could. Most of it left behind almost no sign of damaged paint, it was just a tiny scratch that had spread on the surface over the years. Of course, you can't be too agressive with the scotch brite pad, as it does scuff the paint, but this shouldn't be too big of a deal since you plan to paint the engine bay eventually and you're trying to take care of the engine bay for just a while. If you do this, be sure to keep on top of it until you actually do paint it...a little more WD40 and a rag on occassion will go a long way, especially if you drive in anything but nice weather.
Looking at the bit of engine bay you've shown in the thread, it looks like there aren't many bad spots in the engine bay, it should take well to this treatment. In the areas that are beyond surface rust, I'd recommend painting as little as you can get away with so you can focus on doing a really good job of it. On my Kadett, I did some POR15 in the battery tray area. I pulled all the stops, with the cleaner, etcher, and paint. If you keep it to a small area, it's easy to stay focused on doing the job right. In my experience with POR, if you do it right, you'll never have to remove it. Sure, maybe you'll cover it with proper paint in the future, but you won't have to remove it. If you use a rattlecan, you WILL want to remove it before you paint over it (as it won't bond for E36 M3 compared to real paint)...using a rattle can is fine in the short term, but if this car is a keeper you'll regret it (IMO). Unless, of course, you do really good prep and use really good rattlecan paint...but then, why not do something like POR that will work even better?
Good luck.
Bryce
Thanks. I suppose cleaning as much as possible is the best first option. The areas with no paint will need paint, but maybe not everything.
I had trouble topcoating Rustoleum with "real" PPG automotive paint. The finish wrinkled up shortly after spraying. My vote is to do it once, do it right... how much work is it to continue through and finish it now?
Complete disassembly of the whole front of the car from the firewall forward. It's not in the cards for right now.
Leave it greasy and wait.
When you can do it right, take it all apart, hose it down w/ full strength Purple Power degreaser, scrub it and pressure wash with a turbo nozzle. Let it dry, then full a non-HVLP gravity feed spray gun w/ cheap lacquer thinner and run it at about 75 psi with the fan set to full narrow.
It's a solvent pressure washer!
Use it and small steel scratch brushes to get in all the tiny recesses, then go over everything again starting at the top and going down.
Then grind all the loose stuff and rust w/ Scotchbrite discs in a die grinder and scuff the whole thing w/ purple Scotchbrite hand pads + 240 sandpaper.
Wipe clean, tack cloth.
Shoot with an epoxy etch primer. I like PPG DP140/141, but it's called something different since they took some of the good toxins out.
The prime, seal and topcoat.
EDIT - Hey, I have pictures of this in an update on my Sprite from a few years ago:
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