Rust Mystery

[Bigdav160]

My Suburban came out of southern California but, from the story I got from the previous owner, it spent a lot of time down in Baja.

So my rust problems aren't the ordinary ones.
So I'm curious what caused this rust on the inside. The fender well area looks pretty clean. What the heck was that hole used for? This is on both sides.

I'm not sure what attempts I should make to address it.

[Cobalt964ruf]

hey dav, take a piece of cardboard, size it up to that panel with some scissors. make it as close to the entire panel you have there in the pic. then use the cardboard as a template on some new sheetmetal. then cut out the rusted panel, trim in the new steel and weld it up. I can get into more detail if you wish. have fun dav.

[Franks 72]

Our truck had a similar problem (Canadian winters / road salt) . The patch repair worked well to keep out road dust and water however it masked the underlying decay.I chose to remove the entire crossmember which is at the transition from floor pan to plywood.This was nessesary to get at the rust in the vertical inner body panels which will need to be replaced. Your inner body panels dont look to bad but it is hard to se behind where he crossmember is bolted on.Check it carefully in this area. I have included a picture of the rust damage / patch.
Removing the crossmember is a huge job (spot welded / welded to floor pan) and I would not suggest it unless you have major rust issues. I would be interested if anyone has ever fabricated the inner body pieces since I will need to do this. Hope this helps.

[Cobalt964ruf]

Originally Posted by Franks 72

Our truck had a similar problem (Canadian winters / road salt) . The patch repair worked well to keep out road dust and water however it masked the underlying decay.I chose to remove the entire crossmember which is at the transition from floor pan to plywood.This was nessesary to get at the rust in the vertical inner body panels which will need to be replaced. Your inner body panels dont look to bad but it is hard to se behind where he crossmember is bolted on.Check it carefully in this area. I have included a picture of the rust damage / patch.
Removing the crossmember is a huge job (spot welded / welded to floor pan) and I would not suggest it unless you have major rust issues. I would be interested if anyone has ever fabricated the inner body pieces since I will need to do this. Hope this helps.

Rust always has a larger surface area than visually seen.

[GuyO]

It sucks but where there is water and oxygen, theres rust. And like Frank says, just add salt and the sodium chloride makes it worse especially if the water can't get out like where your area is. Personally, I do not think there are enough drain holes in Burbs or Blazers. Even with Pickups, the fender and door drains are too small and get plugged with dirt or spray on undercoatings. I too would cut it out and weld in a new piece but be careful welding a galvanized patch, heating the zinc becomes a poisonous fume. I have tried a lot of things for rust removal and rust treatment including electrolysis using laundry soda, muriatic acid dips and occillic acid dips for parts. But for body grinding/brushing/neutralizing and patch panels! Good luck, love Burbs! G.

[franken]

No mystery. There was no paint applied to boxed areas, or even hard to reach unboxed areas. So as seen in the pic, the rust comes from inside and you wind up with a painted surface that has almost nothing but rust behind it.

In the mid to late 70's they started using more galvanized metal, and dipping the bodies in primer. This improved things a lot.