Foam inside wheel arches

[Dave Summers]

I've been cutting rust out of the rear wheel arch on my 412, and the cavity is filled with some yellow foam stuff which I presume is meant to inhibit rust as well as absorb sound or vibration. I've dug it away from the immediate area (just a few mm so far) but I'm wondering how flammable it is - I don't want to find out the hard way when welding! Also if I remove a lot of it, what would folks recommend as a good rustproofer to inject into the space once the repair is done? Waxoyl is obvious but if I'm right in thinking the foam is also meant to absorb vibration, there may be something more suitable.
So far I'm on the forward part of the wheel arch, but there's another hole in the inner wing where lots more of the yellow stuff is visible.

[broady_6]

Very incredibly exceptionally flammable. Waxoyl is useless these days. You're better off with dinitrol, it has rust inhibitors in which waxoyl doesn't seem to have anymore. Sound proofing wise, use some dynamat on thr cabin side of that cavity. It will kill the noise very effectively with out the need to fill the cavity

[Chino]

Another vote for Dinitrol, waxoyl is old hat these days, rust prevention has moved on somewhat in the last 50years I've been using a lot of dinitrol recently on another project, ML(if going into existing metal with possible rust present) or 3125HS (if going into fresh metal)for cavities, aerosol with the extra long hose they sell. There are some of the treatments which claim to offer noise absorption, I think Dinitrol 4941 does. It's an underbody black treatment applied by aerosol, much easier to use than traditional treatments and leaves a nice level coating, it's what a lot of manufacturers use in the factory now on underbodies and arches etc. As for other methods, Broady is spot on with Dynamat, great stuff if a bit of a faff to apply.

[richtbiscuits]

I recently cut the quarter panel skin from a 411 variant. That foam extends right round the wheel arch at 2-3 inches thick. I presumed it was sound deadening but it also sticks to the metal pretty well. It's also found it in the cavities at the top of the posts next to the rear hatch at the roof line on variants. I found my rear screen heater wiring stuck fast in it! Perhaps this foam holding water next to metal is the reason the rear arches and roof gutters rot from the inside out!

[937carrera]

I did a small sill repair to my 412LS. I was very careful to pull the trim and carpet away from the inside. The foam tends to smoulder rather than burst into flames,but I was very very cautious with the MIG and water on hand.

Good to see you still drop in from time to time Chino, though you have been away so long I have managed to catch up on your post count

[Chino]

Good to see you still drop in from time to time Chino, though you have been away so long I have managed to catch up on your post count

It’s what brought me back, I’d heard the rumours
You never know, might find myself with another type 3 at some point.

[Aaronslimvw]

Roof flashing makes great soundproofing, and a damn sight cheaper than dynamat. Used it on a couple of mini projects in the past and it works a treat.

[sparkywig]

Roof flashing makes great soundproofing, and a damn sight cheaper than dynamat. Used it on a couple of mini projects in the past and it works a treat.

And me, as long as you heat it gently and use a roller.