Roof Leak in NCV3 with Roof Rack Rails

[lhprod]

Heavy rains in Los Angeles last week, and I noticed several drops of water on the floor of my van, mid-cargo area, as well as on the underside of the ceiling. Both driver and passenger side.

Saw a previous thread where someone suggested using Dicor sealant on a leaky roof. Do I need to remove the factory roof rails to apply? Looks like the rails runs along the entire cargo length of the van, and seems to have Philip’s head (self-tapping???) screws and washers visible on the inside.

 

[sparkplug]

Silly question, but is there any other possible point of entry? Skylight? Any wires or ariels running through the roof?

Water travels in mysterious ways so where it lands isn't always an indication of where it came from.

It's definitely not condensation? Hosepipe test will tell you for sure.

Factory roof rails should be bolted through rather than screwed with self tappers I think.

Either way, I would remove whatever is holding the rails in place and put a generous blob of sika flex around the hole from the top of the roof, re-seat the rail and replace the fastener through the sika flex.

It sounds like you have access from the inside, so I would also put another good blob of sika flex from the inside as a secondary barrier.

I've never used the Dicor but I think you would still need to remove the rails to apply the tape. I have no idea how that would perform if you sealed the existing hole with the tape and then put another screw through it. Maybe someone who has done that can tell us if it works or not.

I've used the technique I described with the sika flex to secure my semi-flexible solar panels through my roof with some self tapping screws and haven't had a drop of water through in 2 years so far.

 

[dharmasprint]

Heavy rains in Los Angeles last week, and I noticed several drops of water on the floor of my van, mid-cargo area, as well as on the underside of the ceiling. Both driver and passenger side.

Saw a previous thread where someone suggested using Dicor sealant on a leaky roof. Do I need to remove the factory roof rails to apply? Looks like the rails runs along the entire cargo length of the van, and seems to have Philip’s head (self-tapping???) screws and washers visible on the inside.

Yes. I installed some rails and even though I had applied sealant between the rail and the roof, I still had water coming in. I removed the rails and redid the job using the dicor sealant, this time at all rivnuts between the roof and rails as well as on top of the rail, washers and bolt heads. Time will tell.

Since you have no idea how the rail was installed, it would be best to remove it and inspect the sealing job. You may have to scrape off the sealant to apply the new sealing material to ensure a good seal.

 

[singletrac]

Mine leaked along the roof seams were they joined the body.

 

[Shawn182]

Seal up the 2 round plastic caps on the roof at the rear of the van to rule that out...that is a very common leak point in Sprinters.

 

[lhprod]

Seal up the 2 round plastic caps on the roof at the rear of the van to rule that out...that is a very common leak point in Sprinters.

Interesting. I will try that first. Thank you!

For those who asked, the vehicle has the factory build sheet option
“D13 - MOUNTING RAILS FOR ROOF RACK”
which would imply that the installation was done correctly.

Ceiling is solid. No fans, wiring, solar passing through the roof. It’s a cargo van without ceiling headliner, so I have full access to everything. Going on the roof to remove stuff won’t be that fun, though.

 

[lhprod]

It's definitely not condensation? Hosepipe test will tell you for sure.

I’m unfamiliar with this test. How is it done?

 

[OrioN]

I’m unfamiliar with this test. How is it done?

Flood the rooftop with water from a hose....

 

[dbenet]

Heavy rains in Los Angeles last week, and I noticed several drops of water on the floor of my van, mid-cargo area, as well as on the underside of the ceiling. Both driver and passenger side.

Saw a previous thread where someone suggested using Dicor sealant on a leaky roof. Do I need to remove the factory roof rails to apply? Looks like the rails runs along the entire cargo length of the van, and seems to have Philip’s head (self-tapping???) screws and washers visible on the inside.

Blast from the past...but I want to following up on the source of the leak and the possible fix. My 2016 low roof crew van is leaking in from the same spot I think. The crew vans have a headliner, which I have not removed yet, but there is visible dirty/water marks on both sides just behind the seam of the last panel. My van has the factory mounted roof rails and nothing else added on roof.

 

[Jades]

Heavy rains in Los Angeles last week, and I noticed several drops of water on the floor of my van, mid-cargo area, as well as on the underside of the ceiling. Both driver and passenger side.

Saw a previous thread where someone suggested using Dicor sealant on a leaky roof. Do I need to remove the factory roof rails to apply? Looks like the rails runs along the entire cargo length of the van, and seems to have Philip’s head (self-tapping???) screws and washers visible on the inside.

yeah, first you have to locate where the leak is even coming from, so people can offer a way to fix it. Usually Butyl tape is used under screws with dicor/flex seal / sica flex over or around the screw

 

[dbenet]

I finally got up on the roof and the points of water intrusion are obvious. There are small cracks in the factory sealant where the horizontal seam of the rear roof panel meets the gutters where the factory roof rack rails are mounted. I also found some rust blooming under the paint along the gutters and above (but not immediately bordering) the windshield. Joy...the van is a 2016 so no longer under warranty. I'm trying to decide whether to take this on myself or have a body shop do it. Anyone have any recommendations for good quality body shops familiar with this issue in the SF Bay Area? Any recommendations on material to replace the entire factory seam sealant?

 

[11hollywood]

I finally got up on the roof and the points of water intrusion are obvious. There are small cracks in the factory sealant where the horizontal seam of the rear roof panel meets the gutters where the factory roof rack rails are mounted. I also found some rust blooming under the paint along the gutters and above (but not immediately bordering) the windshield. Joy...the van is a 2016 so no longer under warranty. I'm trying to decide whether to take this on myself or have a body shop do it. Anyone have any recommendations for good quality body shops familiar with this issue in the SF Bay Area? Any recommendations on material to replace the entire factory seam sealant?

Did you ever get this figured out as far as a repair for the seam. If so what route did you go I have the same issue and need to repair, it. Thanks

 

[dbenet]

Did you ever get this figured out as far as a repair for the seam. If so what route did you go I have the same issue and need to repair, it. Thanks

Yes, I finally took care of this myself. First I tried to get some traction with MB due to the failed factory seam. No luck... they told me to kick dirt since the vehicle is no longer under warranty and I'm the second owner. Then I shopped around various body shops and the quotes all came in astronomically high ($7-8K) with nobody willing to guarantee the work. Most of the shops I spoke to wouldn't even take the job. Finally the owner of European Collision in SF (specializes in commercial vans) gave me some solid advice basically encouraging me to do it myself. He was kind enough to show me around their shop, talk technique and materials. So I did. It was a huge pain in the ass and took 2-3x longer than I thought it would. I stripped the failed seams and both roof gutters down to bare metal, sprayed a 2K epoxy primer sealer and then re-sealed them myself with SEM sealant. Then I sprayed base and clear coat over the seams and roof gutters and blended neighboring panels. I was able to address some of the other body rust in those areas at the same time. Next I did the inside, where the water penetrated and rusted the panel seam. I grinded the rust as best I could with a combination of dremel and angle grinder brushes and wire wheels, then treated with ospho and finally repainted with rust converter. Then I remounted the factory roof rails using a 1.5" butyl tape along the whole underside since the factory gaskets were toast and I couldn't find anywhere to buy them without replacing the whole rail. Everything has been water tight through all these crazy storms and my color match is good enough for the roof and cap rail. I kinda messed up the clear coat in one area, left with a hard masking line and I'm still deciding if I want to go re-do it or just leave it. All in all, I spent about $700-800 on tools and supplies and the project took me a few weeks off and on. Now I totally understand why the shops wanted to charge so much or didn't want to do it all. Next I'm going to put in some insulation before reinstalling the headliner and add some mounting points to the inside of the roof to be able to hang a surfboard inside. Let me know if you want more details about the project.