Spring, when a young mans fancy turns to rust...
 

..... prevention that is.

Just looked up into my rear wheel wells and right at the highest point were some cracks in the undercoating. A screw driver twisted into cracks removed a section about 1 inch by 10 inches long. Only suface rust was visible underneath. A little wire brushing, rust converter, zinc primer, paint and some more Wurth undercoating are all that is needed.

Check your early models and early mid years before it becomes a serious issue!

Ouch... What year?

'74?

Yes, a 74.

This car has a thick undercoating which might be too thick as it lifted off in chunks at the peak of the wheel arch. I removed loose stuff back to the impossible to remove stuff.

It also was Ziebarted in 1974, still have the receipt. And it appears an Arizona/Colorado car almost its entire life. Point being, all areas should be inspected yearly for hidden rust. Even if it looks good, you gotta poke around a bit.

Any suggestions for treating such areas?

Ziebart, eeek, I'm interested to hear how the experts suggest tackling this one too.

OK, so I crawled under my '74 to do something else and sure enough, up at the highest point in the rear wheel well there were some gaps in the undercoat. I poked around with a screwdriver and cracked off some sizeable chunks, same as you did.

The thing is that the gummy stuff up in there was not routine undercoat, but rather some PO's idea of an appropriate sealant. It's almost like caulking compound, but it's hard to tell.

In any case, I want to do a good repair but I'm not sure what to use. Just appropriate paint over the metal followed with Wurth, or comparable spray undercoat seems too easy.

Is there some thick glop that can be squirted up there (it's hard to reach) that will really seal that seam permanently?

Jerome, that gummy stuff was Porsches idea. That is what they seal the bottom of the rear window frames with.

No doubt that is so.

In this case I took a closer look and discovered that there was a layer of closed-cell foam, which was plastered over with undercoating of some sort.

The foam is breaking down, therefore, the cracking. I'll dig it out and reseal somehow.