B-Pillar rust

[pollock]

I found some rust where the B pillar meets the rocker. This is a Texas car, not a northeast rust heap. I had the carpet out for an unrelated water leak and first noticed this rusty spot:




I looked into the base of the B pillar and tore out this stupid foam:



And found a puddle of water and some very serious rust, which I couldn't get my phone camera to focus on:



I tore out the foam on the drivers side and found similar damage. My only theory on how the water got in is through the roof trim clips (half-style vinyl top) and dripping down the B pillar. I have not pulled the headliner yet to see if there's any supporting evidence but I will.

I think I am going to do some surgery and get as much rust out as I can. My idea is to drill out the spot welds, make a cut at the solid red line, and remove this piece. Grind, treat, weld back in, and POR15. Thoughts?

[VicCrownVic]

My '89 MGM was a 50th anniversary edition which had an upfitter put a half cloth top on in place of the stock vinyl. there were holes along where the front edge of the half top trim strip would be that I found when I pulled the headliner after getting a wet shoulder from the water running down my seatbelt. They didn't even fill the holes, just slapped the cloth top over it.

All that to say that you may have a roof leak depositing water in that foam. That area isn't rotted out even on my rot boxes. It could be worth pulling the headliner to investigate if a roof leak might be the case unless your car did not have a half vinyl top from the factory.

[Tiggie]

On cutting it out: That's a very structural part. I would hesitate to cut it, for fear of what would happen in a side impact collision. Welded areas look fine but would likely break instead of bend. If it's just surface rust, not structurally weakened, I would use some type of rust encapsulator on it.
I echo VCV - very likely a B-pillar issue. Does yours have the light on the B-pillar?

[pollock]

On cutting it out: That's a very structural part. ......... If it's just surface rust, not structurally weakened, I would use some type of rust encapsulator on it.

Agreed - critical structure. But the rust is more than just surface. it's enough that bits flake off with pretty minimal scraping. I do hope/plan to use rust encapsulator, but I don't think I can get proper access without cutting my way in there. Then I can really inspect and replace some steel if I have to.

I would hesitate to cut it, for fear of what would happen in a side impact collision. Welded areas look fine but would likely break instead of bend.

Will brittle welds be more dangerous in a crash than rusty metal? Maybe. Seems hard to know for sure. I don't take this lightly.

I echo VCV - very likely a B-pillar issue. Does yours have the light on the B-pillar?

Yes, it has the light. I don't see any evidence of water coming in around the light.

I pulled the headliner last night. It's dryer than a popcorn fart up there. The sealer on the clip fasteners is still visible:



I think all the water is coming into the B pillar itself, from a combination of places. One is where an exterior trim screw penetrates (although not the one visible in this photo):



The main evidence is in this photo, through the rear door hinge and the rear light switch. Also the wiring grommet, just out of view:

[pollock]

Right now my plan is to seal those areas and leak-check them. I'm not 100% decided on the cut-and-weld but I'm leaning that way. The saving grace is that I only have to cut out about a third of the attachment of the B-pillar to the rocker, so I'm not worried about getting it back in the right place.

I'm disappointed in the design of this area. It's clearly not water-tight, and usually they provide an exit path for water. Instead they did the opposite with that big chunk of foam that trapped it and retained it.

[DerekTheGreat]

Might be worth setting up a hose and spraying the thing to see if water isn't also coming in from the B-pillar light. Also, these things weren't designed to last 30+ years, so it did pretty well. All cars have sound deadening foam in the rocker panels and just about every car sheds their rockers when they do start to rust.

[pollock]

I will water-test the lights before I button anything up. I did see a couple small slots in the top of the rocker inside the B-pillar that would allow some drainage, but I guess they were sealed by the foam.

[VicCrownVic]

That picture with the headliner out is jogging my memory. Those plastic cup-like things were just hanging out on top of my headliner. The holes in the roof at those spots were wide open under the add-on cloth top.

Factory drainage slots seem to usually be a spot for rot if the drainage hole gets blocked. As long as they are clear like they should be, they are a good thing.

[Tiggie]

Could also be coming in around where the rear doors bolt to the b-pillar? I'm sure there was originally seam sealer behind the hinge that's degraded.