Question Coach leaking somewhere

[J.Holland]

We have a 21 foot 1994 Gulf Stream Conquest Limited Edition motorhome with a coach leakage problem in the back wall area when it rains. Water drips out underneath the bottom of the right side taillight assembly, and there is a delamination bubble in the rear outside wall about a foot to left of (but not touching) the rear window. On the inside, the head of the mattress where it abuts the back wall, will become soaking wet. When camping, we slightly elevate the back end of the coach for comfortable sleeping purposes, so the coach is not perfectly flat. When the motorhome is moved, water will come out of the bottom corner curb side/back wall. So far we have caulked every possible outside joint, rear window, taillights, ladder supports, and the running lights. Inside we caulked the back wall seam that the head of the mattress touches. We have closely inspected the roof and roof edges and found no visible leaks. There are no visible water stains anywhere inside the coach. As a last resort, we've made an appointment to have the entire roof replaced next week, but we are reluctant to proceed with it because of the age of the roof-top items that will have to be removed then reinstalled. Replacing this motorhome is not an option for various reasons.

 

[AbdRahim]

You may want to check the caulking where the roof meets the side walls. Before replacing the roof I woould have the delamination looked at, opened up and see if there is a hint of the water path. If there is water in the walls, there is likely more problems and potential mold.

 

[Kevin D Pem]

Welcome!

Water is a hard thing to follow. I would be reluctant to replace the roof until I had searched all possible avenues. I can tell you this. Caulking is an owners worst enemy if the job is not done right. By right I mean removing what you will caulk and removing the old and glue with caulk the new item or old item back down. I have in the past removed all the patch on a roof and had the leak disappear without ever applying new patch.

Because of the amount of rain we get in AZ I spent the last year chasing down a leak that wet my bed when it rained. I removed all trim and re-caulked. This did not take care of it, but I found the problem. One of the windows needed to be removed from frame and new sealant, The window is installed like a windshield so the silicone windshield flashing compound was required to stop the leak. such a simple fix was very illusive.

 

[AbdRahim]

Welcome!

Water is a hard thing to follow. I would be reluctant to replace the roof until I had searched all possible avenues. I can tell you this. Caulking is an owners worst enemy if the job is not done right. By right I mean removing what you will caulk and removing the old and glue with caulk the new item or old item back down. I have in the past removed all the patch on a roof and had the leak disappear without ever applying new patch.

Because of the amount of rain we get in AZ I spent the last year chasing down a leak that wet my bed when it rained. I removed all trim and re-caulked. This did not take care of it, but I found the problem. One of the windows needed to be removed from frame and new sealant, The window is installed like a windshield so the silicone windshield flashing compound was required to stop the leak. such a simple fix was very illusive.

How did you find it?

 

[Kevin D Pem]

I left the trim off the window when I re-seated the frame. The next time it rained it was wet on the window frame but not under the frame. The top side of the frame was dry so it was quite obvious by that time in the game. All the other options had already been re-seated.

 

[J.Holland]

Gentlemen - Thank you for taking the time to reply.
Kevin - The window could possibly be central to the problem, and we'll give it another microscopic inspection.
AbdRahim - Although your suggestion is well-taken, we don't want to open up the delamination by breaching the outside skin.
Which brings us to - What is between the outer skin and inside paneling? We can't find any access to look. Is there any way we can find out how the back wall is constructed?

 

[AbdRahim]

If you have water in the wall that is causing the de-lamination and you don't address it, nothing you do will save the rig. If mold grows in there it will eventually become dangerous s to your health, not to mention spreading of the rot. Not trying to discourage you, but embedded unaddressed moisture will destroy the rig. The longer you let it go, the more it is going to cost to repair.

 

[Amoque]

I had an elusive leak in our 2 year old Komfort. There are ways to check... Infrared can determine the temperature difference between wet and dry and help you find where wet patterns touch windows, seams, or other likely weak spots. I didn't do this, but it was recommended by my dealer - cost, as I recall, was reasonable.

Mold can be found by drilling small holes at the top and bottom of a wall or area and filtering the air collected for spores. Also reasonably priced as I recall.

Our leak was a factory defect. Along the high edge of the side was an aluminum trim/ rail screwed just below the roof to hold the roofing material in place. A thin metal strip (resembling a mini-blind slat) slid into grooves in order to hide the screws. At the factory the aluminum had been misplaced, then drilled. When the mistake was discovered, they moved the aluminum and re-drilled the holes - without patching the erroneous ones before sliding the slat in to cover the error.

The result? Water ran in torrents down the bedroom walls when it rained.

 

[Kevin D Pem]

Gentlemen - Thank you for taking the time to reply.
Kevin - The window could possibly be central to the problem, and we'll give it another microscopic inspection.
AbdRahim - Although your suggestion is well-taken, we don't want to open up the delamination by breaching the outside skin.
Which brings us to - What is between the outer skin and inside paneling? We can't find any access to look. Is there any way we can find out how the back wall is constructed?

This may help.

Laminated Construction

Learn how Gulf Stream Coach pioneered the vacuum-bonded laminated fiberglass walls used in our Motor Homes and Ultra-lightweight travel trailers. It's important to know that we build our laminated walls in-house, in our own facilities, using materials and processes that we have perfected over...

www.gulfstreamcoach.com

for the record, if the material under the outside plastic is plywood it is likely the plywood de-laminated. Think windshield repair method using tite-bond for glue. I have not done this but I am thinking it should work.

 

[J.Holland]

Kevin - Unfortunately, Gulf Stream's current laminated wall construction indicates that they now use 'Azdel', which wasn't in use yet for RVs in 1994. Per Azdel's website, it's only been in RV use since 2006. We're still curious how the leak seems to possibly run laterally.
To all - We've decided to cancel the roof replacement appointment and we intend to more closely inspect the rear window seal, caulking, etc. However, living in the NE means that Spring wavers between late winter and early spring, with heavy rains and more snow, all for probably a few more weeks. All that being said, we'll have to wait for some warm and dry days to do the inspection. We will certainly update this thread with our findings and (hopefully) the resolution.
Thank you to everyone for all of your suggestions, thoughts and theories. It's extremely nice to know that you're so willing to help.