I've been chasing a leak in my Zinger for over a year. The water would come in the front, door side bedroom closet during heavy rains. I thought it was the marker light directly in front of the leak so I pulled it off and put new butyl tape and caulk around it.
It still leaked. I put new Dicor lap sealant on the front cap seal. No help. I recaulked the corner molding, still leaked.
Finally I had enough and built a pressure tester using a high velocity ventilator from Harbor Freight.
It basically pumps high volumes of air into the coach.
You then take soapy water or kids bubble solution and spray all around the exterior. Where you see bubbles is a potential leak point.
What I found was the plastic gutter extensions on the end of the drip rails leaked air profusely. The water would overwhelm the gutter and flow back behind the gutter, behind the aluminum skin, finally dripping into the closet.
My thoughts are using an RV cover during the winter pulled the extensions down breaking the original seal.
After seeing this, I tested the other three extensions. No surprise they also leaked a lot of air. From what I've read these gutter extensions are a common place for leaks to originate.
Another place where I had a leak was the top bulb seal on the slide out room. I spotted this when I noticed the staples in the wall board that the slide out seals up when open were starting to rust. The bulb seal looked like it was sealed by the factory with silicone sealant. The silicone had pulled away and was allowing water to enter past the bulb/sweeper seal and into the camper. The wallboard would wick the moisture up and rust the staples. I cut away as much silicone as I could and laid down a fresh bread of Dicor lap sealant to close it up.
After sealing these areas up, Iíve been leak free. I still pressure test the trailer once a year. Along the way I have become proficient with a caulk gun and can recommend the following sealants:
Roof - Dicor self-leveling lap sealant or Eternabond tape. The only thing about the tape is it is 100% permanent. If you place it around a vent or antenna and need to later remove the vent/antenna, youíll have a heck of a time trying to remove the tape. It also requires a clean prepped surface. If there is a spot that wasnít prepped correctly you could have a leak under the tape.
Sides - ProFlex or OSI Quad. I recently started to use OSI Quad after my local dealer ran out of ProFlex. The advantage is you can find OSI at Lowes or Home Depot, it cost about 50% less, and is easier to work with.
Hopefully my experiences can help someone else looking for a leak or potentially stop future leaks.