It's usually a symptom of a leak...injecting glue will not work. Fixing the leak (it could migrate from anywhere...roof sealant failure, clearance light sealant failures, antenna, etc.) is the #1 job. Hopefully it isn't so advanced that it will continue to grow!
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You will probably find out that it is poor application of the fiberglass at the factory (delamanation) and now, due to pressure from the wind and road bounce it is breaking loose. I had a serious problem on my 5th wheel where the cap would actually sink in from the pressure of the wind. If I did over 50 MPH it would just cave in. When you stopped it would just pop out. Weird. Go to MY PICTURES below and see what I had to do to fix it. Fortunately my closet is there and I could get access to the cap.
It is going to be a tough fix but will probably have to be done from the inside -- unless you want to get into taking the cap off.
2008 F350 CC 2WD LB 6.4 Lariat Auto SRW, Retrax, AirSafe Hitch, Train Horns, On-Board air, RideRites, Aux Tank, 19.5 Michelins
Yep--Bigdon has the right idea and yes---drilling a very small hole and injecting an adhesive will work but you then need to set up a way of putting external preasure on the area. The only fix that worked on my unit was replacing both side walls. Good luck
My dad had a 2008 Flagstaff by Forest River that this happened to and the roof had leaked. It was out of warranty and Forest River took it back to the Factory and replaced the roof, all side walls, front and rear caps as well as some of the interior. He had to pay for the transportation. He traded the Flagstaff for a 2012 Flagstaff and when it arrived back at the dealer they sold it. You have a leak...
While it could be a leak, it could also just be delamination because the factory did a lousy job sandwiching the wall together. Look first for a leak, including from around the edges of the roof and windows. If you can, try to find a leak by sounding the inside wall area to see if you can find soft spots or other evidence of leaking. If you are sure you don't have a leak, then injecting glue behind the fiberglass might fix your problem. But, you have to devise some sort of giant clamp to press the glass against the substrate.
2002 Keystone Cougar 286, 8,400lbs loaded, pulled with a 2004 F150 Supercrew, 5.4, 3.73 gears. Retired and enjoying life
Perhaps someone can help with a related question. On my 07 Jayco Designer cap I have some fine cracks in the fiberglas near the ends of the lower raised horizontal bar. My guess these three bars are for structural stability so you don't have a flat surface facing the wind of road travel. I got some "Insta-glas" that cures by UV, but have not put it on yet. (i'm a little skittish). I see no signs of water leakage and they look like crows feet on the sides of your eyes when you get older. I thought they were hairs, when I first saw them. Thanks, in advance for the help. david
2007 Jayco Designer 36RLTS
2006 F350 DRW super duty
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