Am about to embark on the rust repairs to a 76 bug which has the expected rust in the C-pillar around the black plastic air vents on both sides.

Obviously the offending sponge material will all be removed and new metal will replace rusted sections.

Once this has been repaired, what do people do to prevent future rust?

1. Weld cover plates over vent holes
   
2. Put in new vents with seled back side to prevent water entry
   
3. POR15 the interior sections
   
4. Other
   

do NOT replace the foam

once you cut it open to do the rust repair scrap and dig out all the foam towards the engine compartment as well

you can disolve the residue with some CRC carby cleaner but it will run down inside the car

use Wurth Wax to protect against futher rust

Put up with the noise its not that bad

Our cabrio has little triangle shaped pillows that stuff up in to the cavity to reduce the noise. It seems to work well. They are made from offcuts of the headliner material with some padding inside it. Each side of the triangle is about 150mm long if that helps.

Yogie

Yep, dont put in more foam, and the pillows is what vw did in the earlier cars, before the moisure trapping foam. The problem isn't the actual foam but the condensation that forms inside the roof and runs down the gutterline can't get out. The vent doesn't cause the rust either, so only remove it if you want the smooth look, when prepped, painted and rust proofed properly, you wont have any drama.

Thanks for all the feedback guys. It all helps!

you can shoot foam back in there if you like but just make sure its the new closed cell stuff not open cell

open cell is the old stuff that holds water


it actually does make a fair difference to noise/dust/fumes in the cabin, i dug it out of one of my old bugs years back

I opend my C pillars up from the inside to get rid of the foam. After getting it out and seeing the damage, I would not put more foam back in - open or closed cell. Either would hold condensation against the metal and the nasty rust would come back again from the inside.

I am cleaning as much of this off as I can with a flap disk, welding in new metal and then giving the inside a good treatment and coat with POR15

Without the foam may be noisier, but at least my bug will be pristine!

I Know someone who has no rust in his pillars but to rust prevent it to , He drill a small hole on each side under the gutter where the top of the door sits and sprayed fish oil in it untill it was coming out of the back vents but he is also now going to weld up the holes he drilled and weld up the vents. The vents dont do much anyway and i reccon it looks better without them and also no rust that way. From Dylan

Hi

Jak Rizzo filled his vents but kept the indent, I think this looks better than completely removing it.

On the A pillar cut the very bottom 1 or 2 mm of it, that lets crap fall straight though and stops rust forming.

Steve

Lee , Is it realy nessesary that you put a picture of your bug in every post. it would be clogging up the forum a bit and wasting bandwidth. Why dont you just put a picture in your signature.

From dylan

Guys, does the vent actually serve any purpose on late model bugs or is it purely aesthetic?

its there for 'flow through' ventilation.

OK started work on C-pillar rust today and dug out this materilas that is carcinogenic to bugs.

OK now my question, I managed to dig out the spongey crap that I could access via the engine bay, but I noticed a slot where it seems to go down behind the wheel well. How do I access that area to get the rest of the spongey crap out? See image for more details.

You might be able to get at it from behind the trim panel inside.
When I did mine I cut a access hatch on the inside of the c-pillar where there is a ~15mm hole. You would have to remove the hood lining to see it.