The Truck Camper had a chronic window frame leak

When I finally pulled the window on my Bigfoot, I found that it was sitting in the lower rear corner of an oversized hole in the wall. This left very little of the flange in contact at the upper front corner, and no amount of caulk was ever going to fix it. With a few wooden spacers, I was able to get the window centered with flange coverage all the way around. Like the others that have suggested it, I recommend pulling the window and re-taping.

It's been raining pretty good over the last several days and the drip rail over the window is performing perfectly. The window below the rail is dry and the area inside where I could feel dampness is dry. I know I could have caulked the window again or used butyl putty tape but it would probably fail again. I consider the drip rail to be a permanent fix. There are also drip caps available through say Camping World that can be ordered to size. I needed mine now so aluminum angle was the quickest available option.
So there you have it, Success!!!

I had one of those leaks on my truck camper with the over the stove vent, it is SOOO frustrating. Of course when it is dry outside no leak, you get rain and it leaks, you repair it and by then the rain has stopped and of course the leak stopped, starts raining and the leak starts. If I had a garage to take it into during the rain to work on it it would have been better but I didn't.

The WOW moment was during a bad rain storm and it started to leak, I was able to track the little stream of water to the vent so I took the fan and light off inside and started to poke around with a flash light like I had done so many times before. This time I saw the water coming in and running along the side of the cut so I cleaned the cut with a rag and bingo there was a little drill hole that they put in when building it that the water was traveling through. Fixed it, dried everything up and no more leak.

I hope your idea works as sometimes there is no obvious problem/fix so you just have to work on possible solutions.

well best of luck apparently you got it figured out.

Vinsil wrote:
Yes, but you still have a failed seal and water will still get in.Going down the road, your camper gets pressurized and will actually pull water into the easiest path, and a failed window seal is exactly that. So while your gutter idea works for stationary use, going down the road will still show it leaking.

Like it was said, pull the window and use the tape. It's not hard to do and it's the only proper way to fix the leak.

My pass through window is open and the fan in the cab is always on blowing in. It may not be enough to pressurize the TC but it should reduce the vacuum. Having the drip rail over the window, water is never going to reach the area in question to get in. Also, driving down the road, the vacuum is going to be drawing out, not blowing in depending upon wind tunnel tests to determine where eddies of high and low pressure form along the sides of the TC. Certainly the back wall and door will be a low pressure area and the sides may have high and low zones but I don't think it's going to be significant so water penetration is less of a concern when driving not more.

The rains start back up on Tuesday and I am ready to either have a large celebration with fireworks, or consume a generous portion of crow. I'll update after a few days rain to give it a good chance to fail if it's going to.

Yes, but you still have a failed seal and water will still get in.Going down the road, your camper gets pressurized and will actually pull water into the easiest path, and a failed window seal is exactly that. So while your gutter idea works for stationary use, going down the road will still show it leaking.

Like it was said, pull the window and use the tape. It's not hard to do and it's the only proper way to fix the leak.

Kayteg1 wrote:
The awning mounting trim sure is big suspect.
I had that on my Lance, what coming from dry climate had relatively low dryrot, yet the beam above slide was completely rotten. Good roof.
Doing the repair I figured out the manufacturer never put a seal on awning trim and water penetrated via screw holes.
I triple caulk the trim on the top.

I tried that already. Replaced the screws with stainless versions and embedded in caulk during reassembly both upper and lower mounts. The wet area is only below the window. I just began to think that there was too much water going over the area. It's like every time it rains, mother nature is holding a running garden hose over the side of the window non stop, flowing down the window and over the lower mount. I'm preventing that volume of water from getting there now.

The awning mounting trim sure is big suspect.
I had that on my Lance, what coming from dry climate had relatively low dryrot, yet the beam above slide was completely rotten. Good roof.
Doing the repair I figured out the manufacturer never put a seal on awning trim and water penetrated via screw holes.
I triple caulk the trim on the top.

I did not try removing the window and installing butyl tape. I was able to press hard against the siding and get DICOR behind the frame. There is no visible crack in the caulk right now yet there is still a damp spot forming in the wall below. I decided a possible entry could be that from where the awning mount is at the roof edge, it forms a dam and all the water that should be pouring out the end of the gutter is forced to pool then surge over the side which is directly above the edge of the window and the bottom mount of the awning. When it rains, there is a constant flow of water going over these two locations. There is the possibility that water could be surging the bottom of the window frame and back flowing in through the windows weep holes. I have seen water accumulation in the bottom of the window before. I decided to install this drip rail to prevent water from ever getting to the window or the awning mount below. This was the only method that fixed a problem on the other side of the TC and it will work fine here too I'm sure. Function over beauty at it's best.

I hope the OP’s fix works. This might be something to try if it doesn’t.
My trailer had a window of that type which developed a leak on the upper corner. The problem behind the leak was that for ease of installation, the manufacturers make the opening significantly bigger than the window (obviously it has to be bigger). As long as the window is installed in the center of the opening, there should be no leaks as the corners are covered. Over time though, the vibrations and jolts can take their toll and the window can shift downwards. If this happens, gaps will occur at the upper corners, and water can infiltrate.
My fix was to install plastic shims beneath the window to prevent it from sagging. I made the shims from a piece of PVC trim I had laying around. When inspecting the window, if you see a gray shadow just above the top of black trim, then the window has probably sagged and it’s time to reset the window.