How to prevent leaks in the cabover area?

I had a problem with leaks in the cabover when my motorhome was new. I took it back to the dealer after our first trip and had it "fixed" under warranty. When it got back I parked it for the winter, and when we took it out for the first trip in spring water was dripping on my wife's head whenever I made a turn. I took it to another repair shop and had the roof completely resealed ( now only 2 years old). At our next trip, water was again dripping into the cab area. I got a ladder and began caulking around the window and lights when I discovered that the marker lights across the front of the cabover were installed upside down. the vent hole which was supposed to be on the bottom of the lights were at the top. As water was running off the roof at the front, it flowed into the vent holes filling the lights and running into the RV wall. I removed the lights and reinstalled them correctly and have had no problems since.

I put Eternabond on all of the roof joints when I got my Pace Arow. It does not look bad when on the side seams. I ran it down to the top of the gutter piece and as far into it as possible, about 1/2 inch. I never had a leak in that MH. Fortunately Newmar is not subject to that problem. I found that the Eternabond stayed white and didn't need cleaning. The rain did that for me.

You can apply new Dicor right over the old, if it's still sound. Just clean the existing Dicor with lacquer thinner and it will look like new. Try not to get any of the cleaner on the rubber roof.

Agreed on not using EB on side windows. Use butyl tape on those guys. Works great and it's designed for that purpose. I would for sure use it top side on the long roof seams. Put it under the side mouldings and with a long overlap onto the roof. At sale time, I would see that as excellent preventative maintenance. It is also easy to inspect. Dicor dries and has to be scraped back in order to re-apply. You don't reapply with eternabond. It actually does stretch/move with the body and self seals. Applying around corners does require some "work" to get things right, though.

I also think you should put Alex around the top and leading edges of your windows. That is where gravity and wind pressure try to push water in. A little extra protection to help the butyl tape is welcome in my book.

Jose

Most Class C's that I have seen that have evident leak problems that you could tell from the outside had windows on the front or some sort of damage to the cab that had been repaired.

Please, don't rush into an Eternabond job. I say that even though I've applied it on all 3 of the RVs we've had. My opinion is that it is great for the main seams between the roof and front and rear caps. Those seams are tough to seal. Two flat pieces meet at joint, then they lay a molding over the joint, with butyl putty tape under the molding. They drive screws through the molding into the structure below. Then they drizzle copious amounts of Dicor self-leveling lap sealant over the whole thing, paying special attention to the screws.

For whatever reason, those seams must be under a lot of stress, because they often show signs of separating. Being relatively flat, they are easy to cover with EB tape. Well, somewhat easy. A 6" wide strip would probably cover one of the seams in one pass. I've had to use two passes with 4" tape to get an effective coverage.

However, I would NOT use EB tape on anything running along the sidewalls. For one thing, it is a bit unsightly, and also it says "LEAK!" to anyone who sees it. Make no mistake, it's not easy to apply around a curve or other non-flat surface. It does not stretch.

You could simply keep an eye on the Dicor up there, and if any cracks appear, put more on it. That's probably what the rental companies do with their fleets. I hope Mocoondo will chime in.

There are windows everywhere on the body, so I don't see why the side windows up there are any special risk. Front windows, yes, they are a problem area, but you don't have one. To me the biggest risk area is the corner trim running along the underside of the cabover. The side leg is open upward, so water is always trying to run inside of it. You prevent this by applying Proflex RV caulk along the top edge of the trim. Continue on up the front lower radius till you get to a point where the trim edge is vertical or angling back upward.

To illustrate, consider trim on a cabover shaped like this symbol >. The lower leg would catch water, the upper leg would shed water. There is putty tape under the trim, but the caulk adds another layer of protection. Also, any exposed screw heads are a problem. Why they do that, I don't know. Back each screw out a half inch, put a dab of Proflex the size of a pencil eraser on the screw threads, and screw it back in. This will definitely help in the long run.

Another issue is the rain gutter. A layer of caulk along the gutter:roof seam is a good thing. Depending on the situation, the caulk might be Proflex, or Dicor (if it's sealing against the rubber roof surface. Same comment on exposed screws.

That pretty much leaves the running lights. You'll have to look them over, take the lens off one, and see what you think might need to be done. Some are amazingly leaky.

My 21QB had no caulk at all on the rear clearance lights. Each one had water behind it already (2014 model) when I removed them before I sealed them up.

The front clearance lights are on an angle. As time goes on they the lenses can fail to drain from dirt and stuff in the fit between the lense and light body. Then accumulated water will run in the spaces around the bulb and socket.

Some people cut a small notch for more drainage. Some seal the bulb socket and hole. I did the latter.

The tape comes in two flavors. One is stark, glossy white. The other (I have not tried) has some kind of textile surface and is supposed to accept paint. So you could put it on, screw down the aluminum corner stripping and edging, then finish with a matching paint.

Jose

Since you have no front window you are probably in good shape. The marker lights should be caulked. Probably check each year and caulk if necessary. The windows on the side are like any other window on the RV.

Wow! Tape is even easier than a caulk gun! This board is so awesome! Thanks for the tips on what brands and products to use.

I'm not much on heights, but I think I may hoist myself up that ladder and take a look around up top, and see what I can tape! :D