Check your roof channels/welds

So I was mucking around with my snorkel and A-pillar trim when I noticed the roof channel trim was wonky. Decided to take it off and have a look.

When I did that I discovered that the weld seam was covered with some type of "sealant" (quotes because it's apparently actually fairly porous and good for nothing but helping the metal rust) that was starting to bulge up and crack in several places. A bit of picking with a screwdriver and...






Thanks a lot GM. I know I've seen earlier model H3's roofs that did not have this stuff on it. Maybe they started adding it in 2008? At any rate, it is crumbly and chips right off no problem. Almost seems like a type of dense celled foam? Looks like it should only be used for interior applications though. All it seems to do is hold the water in and help everything rust. The good news is that it is super easy to take off. The bad news is this is yet one more thing to deal with. My plan is to strip it all off, clean off the rust, prime and paint it, then seal it with some high quality urethane roof sealant. Probably something like what is used on RV's.

That of course was not the cause for the roof channel trim being wonky, it's just getting old and warped is all. I'll eventually replace them but they're over $200 a side, mainly because they include the U channel for the roof rails.

So y'all might want to pull your roof channel trim up and check your weld seams. If they are covered with this stuff then odds are it's starting to rust underneath. If not then they might be rusting anyway. Could also be the source of leaks some people without sunroofs are getting.

Ugh, why you gotta give me more work?

It's a urethane seam sealer. Cars have used seam sealer on the roof gutters since the 60's. But in this case it's a larger (wider) strip b/c the center panel 'skin' is attached to the top edges, it doesn't wrap over the roof edge as in the old days. In the old days if the seam sealer leaked (and it often did), it didn't result in water leaking into the cabin. The reason they attach the roof like they do is b/c roof-crush strength regulations have become more stringent (for safety), but that means to make the main structure strong enough designers create more of a 'cage' type passenger cabin construction, and they attach the roof skin to the top. I'm sure it also comes down to ease of assembly. Lot of roofs are even glued on. Not just GM.

Yeah, mine was similar to yours. A good source of roof leaks and soaked (rotting) floors. Like you say ...inspect and remedy any cracks. Good post.