Are there any common leak points?

[ChefExcellence]

I've just had to have a friend weld the drivers side sill and replace some of the side panel on my van. It was an inside out job as water had pooled there for so long and eventually split the steel so there seems to be water getting at it from somewhere but I can't figure out where its coming from.

Does anyone know if there are any common leak points on these vans as they get older? It's a 2001 Berlingo 

Thanks

[notsofast]

I had exactly the same issue on the same age of van and had it welded a couple of years ago.  I had assumed the cause was condensation.  I often carry quite damp cargo and it's sometimes so moist inside the van that on cold nights the inside of the roof can get covered in drips, and I assumed this condensation had just slid down the inside of the side panels and thus caused the problem. It's hard to see how water can get in there otherwise.  Is your van plylined?

[ChefExcellence]

Yeah mine is ply lined, although I've taken all that out when trying to see where the leak was coming from. I have sealed around the roof rack brackets now and also fed some sealent into a few small cracks on the existing one, so far there's no new brown streaks coming from it so hopefully that's solved it, but time will tell!

[RattyCortina]

A couple of small drain holes might be a good idea.

[notsofast]

Was water coming in around the roof rack brackets?  Mine all look fine. Though according to this video, apparently they can rust and cause water ingress inside the vehicle: https://www.youtube.com/watch?v=VvhFsR4j7dk

I never plylined mine - because of damp cargo, I was concerned about drilling into the metal and not easily being able to check the floor (though plylining would've protected the sides and perhaps reduced condensation). But it's interesting that plylining (or not) doesn't seem to have influenced this particular issue.