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Topic: Roof/Front cap seal leak (Read 1391 times) previous topic - next topic

Roof/Front cap seal leak

Just this weekend, noticed that we have a bit of water coming in what appears to be behind the passenger side trim where the front window accordian covers stows. Ultimately to make it down around the carpeted area just inside the right door edge by the 12vdc disconnect switch. That area between the windshield and the Door. Not much up on the roof in that area other than the seam where the front cap, overlaps the roof. We have had alot of heavy driving rain in the past week, and she is 21 years old.

Opinions/Facts?

Ive been working on a fuel hose replacement and Fass install, so my attentions were there until going inside yesterday to pull the cable for my new fuel pressure gauge. If pretty today when I get home will go up top to see if anything obvious.

Thanks, Mike
Mike in AL
2001 U295
8.3 ISC 350
Build 5918

Re: Roof/Front cap seal leak

Reply #1 –
I had same waterfall.  The joint between the roof, side, and top fiberglass meet is caulked and covered with the aluminum strip screwed into the aluminum/steel framework.  These joints flex over time and need addressing at this 20 year point. 

When I pulled the front cap strip to install the ZipDee awning mod, I discovered this gaping hole in the caulk where all 3 surfaces intersect.  This is the corner above the entry door, and looks like it had been leaking from the factory as you can see by the clean area where water was flowing freely into the coach through that 1/4" gap.

2001 4010 U320 build #5865 "Bluto-d-Bus" since 09/18
2006 Honda Element ESP Toad
Full timing since 2016 in Western MT
Copilot: Sitka
1975 GMC 260 Avion: sold

Re: Roof/Front cap seal leak

Reply #2 –
Pyolet,
Many thanks. Figured it was being caused in that area. Thanks for the detailed image. Know what I need to do.
Mike in AL
2001 U295
8.3 ISC 350
Build 5918

Re: Roof/Front cap seal leak

Reply #3 –
Probably time to pull the front cap trim strip off entirely. Clean, inspect, reseal, reinstall.  No reason to not do a complete job.

You can put a blue painters strip on either side of the trim piece before removing it. Leave 1/16" to 1/8".  When you reinstall the trim it makes clean up easier.  Use plenty of caulk, I used 3M 4000 UV. There are other caulk options for this. Put caulk in every screw hole and on the screw threads. 

Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Roof/Front cap seal leak

Reply #4 –
Also check porch light seal.
Dan - Full timing since 2009
2003 U320 40' Tag 2 slide

Re: Roof/Front cap seal leak

Reply #5 –
Not sure about Mike's water leak, but wanted to share that when pulling a cable, it is a good idea to pull several spares at the same time.

We once pulled about a dozen, of different types. Twisted pairs DC-amps, coax video, jacketed, #18, #16.  Used most over the years.  (2nd camera, pyrometer, boost, fuel pressure, A/C compressor, start battery volts, delay engine start, etc.)

Re: Roof/Front cap seal leak

Reply #6 –
Roger,
Plan to do exactly that.

Dan,
Good point

Barry,
Did just that AND from the Engine area mouse access up to the Front mouse access, brought a Nylon cord with them and left it in place for the ever next time. I pulled a cord along with the first of the fuel lines I replaced as I had to add a new 3/8 return line for the fass system. When that new 3/8 fuel line was done left that cord in place for the electrical and still in place for the future.
Mike in AL
2001 U295
8.3 ISC 350
Build 5918

Re: Roof/Front cap seal leak

Reply #7 –
"Practical Sailor" put out some info about 3M 4000UV and an apparent failure over time. Here is a link to some info. I don't know if the issue is limited to certain batches, but certainly something to watch out for...
PS Seeking Reports of 3M 4000 UV Failure - Practical Sailor
Don
Quote from: Roger & Susan in Home2 –
Probably time to pull the front cap trim strip off entirely. Clean, inspect, reseal, reinstall.  No reason to not do a complete job.

You can put a blue painters strip on either side of the trim piece before removing it. Leave 1/16" to 1/8".  When you reinstall the trim it makes clean up easier.  Use plenty of caulk, I used 3M 4000 UV. There are other caulk options for this. Put caulk in every screw hole and on the screw threads. 


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Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

Re: Roof/Front cap seal leak

Reply #8 –
Some people here have recommended a Sika sealant instead of the 3M sealants. Any recommendations on which Sika sealant is preferred?
David and Carolyn Osborn
1995 U320C SE 40' Build 4726 Feb 1995
FMCA 147762
Motorcade 17186

Re: Roof/Front cap seal leak

Reply #9 –
I know my cousin who is a boater swears by Sikaflex
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Roof/Front cap seal leak

Reply #10 –
Sikaflex  is good stuff, but there are many different versions of it. I had a few tubes of it left over from my new metal roof on the house a few years back, #221. I know for a fact this one does well on anything that might move a bit yet stays flexible almost like many silicones, but not easy to remove or break loose. As I got home with a few hours of daylight, removed the 3 front cap strips this afternoon, cleaned all the old off and scrubbed down with acetone to get it clean and residue free. Did find a few spots in the area of the leak where the old had turned loose and had a few small cracks in the sealant. No visible gaps between the roof and the front cap. Front was well over the top of the roof as well as the sides.  Probably do the rear trim in a few weeks. Thanks for the input folks.
Mike in AL
2001 U295
8.3 ISC 350
Build 5918

Re: Roof/Front cap seal leak

Reply #11 –
Thanks for mentioning the rear cap. I was curious if they were ever a issue also. So it looks like this has made the preventive maintenance want to do list.
Thanks Scott

Re: Roof/Front cap seal leak

Reply #12 –
Quote from: Don & Tys –
"Practical Sailor" put out some info about 3M 4000UV and an apparent failure over time. Here is a link to some info. I don't know if the issue is limited to certain batches, but certainly something to watch out for...
PS Seeking Reports of 3M 4000 UV Failure - Practical Sailor
Don

I have had good performance from 3M 4000 UV over the last 10 years. I have never seen the issue reported in "Practical Sailor". As they say these may have been older applications, maybe before 2018 when 3M reformulated the caulk.  The exact uses where these issues occurred and how it was applied and used in what conditions are unknown.  But they are a reminder to do a visual check on your coach at least once a year.

When I painted my roof last summer (2021) I had to remove my TV satellite dish. It was mounted with screws and 3M 4000UV. Screws came out and I had to cut all of the places where the 3M 4000UV had been applied.  Seemed pretty tough to me.  The satellite dish was mounted in about 2012.

I used a clear SikaFlex when I redid my shower skylight. It is holding up well. My recollection was that is was runnier than 3M 4000 and didn't result in as neat a job as I usually try to do.  OK though, it is on the roof.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Roof/Front cap seal leak

Reply #13 –
Scott,
No issues seen yet. at the moment just a desired PM as this one issue came up. Would have done the rear also last eve but ran out of time. I checked over and patched the entire roof penetrations last year when I did the new fridge/stove vent caps, but did not do these end caps.

Roger,
Ive heard great things about the 3M, and usually use top end stuff like that. But just so happen to have the tubes of Sika left over from that roof job. I also have a few tubes of windshield install urethane rubber, but that stuff being black is really easy to make a nasty mess. Some of the Sika is down right thick, this stuff was about like silicone but thicker. I think anything rated for Marine use, even high end silicone, would fit this application as long as the old is well removed and the surface is well cleaned with acetone or similar good fiberglass cleaning solvent....the stick is only as good as the prep...What I removed looked like a cross between basic thumbgum and dicor self leveling but very old and and some places a bit hard and cracking, yet some spots appeared a bit gummy which was odd for the age. None appeared to have been anything other than OE work.
Mike in AL
2001 U295
8.3 ISC 350
Build 5918

Re: Roof/Front cap seal leak

Reply #14 –
I am going to redo the top of my rear cap this spring. I had a leak from there late
last fall and I temporarily fixed it with silicone. I will remove the strip and clean it
and I plan to use Sikaflex when the weather gets good. 
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Roof/Front cap seal leak

Reply #15 –
Mike,
See Sikaflex® - The Leading Brand for Sealants and Adhesives | Sika
My experience with acetone on gel goat is that it seems to discolor the gel coat, almost like bleaching. Use sparingly.  Gel coat ends up lighter color, whiter.

I would suggest not using a silicone based sealant. Residues prevent almost everything from sticking the next time including silicone. Polyurethane should hold up longer and give a satisfactory result.

Lots of options, lots of opinions, a variety of results.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Roof/Front cap seal leak

Reply #16 –
Roger,

would tend to agree, Gel coat being a final finish, too heavy of usage of a solvent such as acetone could lead to a bit of fade affect. I would never recommend it for general heavy cleaning or any phase of a deep detail by inexperienced individuals.. Rather to be used for excellent adhesion promotion to an area that is never to be seen. The seam in question would be such a place. I would never recommend to anyone to use it as an overall cleaner for say a deep detail. Those that know how to professional detail, it is however a valuable tool for certain blemishes.  Acetone also happens to be a preferred method of cleaning stubborn stains on fiberglass boat hulls.  BUT, must be followed by a wax or sealer, or the hazy white appearance will come back.

I normally would recommend a oil/grease remover, such as Nason 441-05 or House of color KC10 for substrate adhesion promotion. However, I have been detailing and painting vehicles for near 40 years as a hobby and have found that these products do no work well on fiberglass as a prep for an adhesive/sealer. Alcohol does better, acetone works best.

After last nights storm. The reseal of the entire front cap joint appears was not my problem. I removed the bulk of the interior trim in that area this afternoon, this weekend I will get on the roof with a hose and have my wife watch the inner trim free areas to see where its coming in. Horn is too far center, if its not the main seam, must be something around the main awning or door trim. Or as Dan Mentions, the porch light.
Mike in AL
2001 U295
8.3 ISC 350
Build 5918

Re: Roof/Front cap seal leak

Reply #17 –
@mkc1962 Did you ever find the location. I have a 2001 that started to have the same leak.

Re: Roof/Front cap seal leak

Reply #18 –
The trim / cap screws are structural...
 I removed the trim and used a structural glue to hold the cap on with rivets . Then reinstalled the trim  with additional sealant .
This stuff is the real deal.  Engineered for windshield install .