roof water leak

[amigomillers]

We have a non-slide 2001 royale. There is a water leak which presents itself in the window treatments behind the drivers seat and back to the galley. We have resealed the horizontal seam on the roof on that side, but after the last rain, the window treatments were soaked again. We would appreciate all suggestions. He cannot SEE where the water is coming from. Thanks

[Gil_J]

Water leaks can be one of the hardest things to find. Prevost uses a huge high volume blower to pressurize the coach. Then they do the soapy water treatment to any potential leak area. If you have Prevost OTR air it's possible to create enough pressure to do the same.

Based on where the leak comes into the coach, the orgin can be anywhere on that half of the coach. Basically, anywhere that gravity could lead the water to where it's visible. This could include the seams and rivets of the front and rear caps. It could be from the roof air gaskets, if you have roof air. Any roof penetration on that side of the coach has to be suspect.

If the leak wasn't limited when it rains, the roof air drains can also be the source.

Sometimes it can help to have an inspection camera. They have a camera on a flexible shaft that's a couple feet long. It may be possible to get it into the ceiling through vents or lighting housing and find the water trail.

[Joe Camper]

If u have OTR A/C there is a simple way to pressurize the bus to soap up seams to check for leaks. Just open the bay door for the evaporator on the drivers side while the ac is on. Its that simple. Insead of the 2 blowers in there recuirculating the air they pressurize the cabin with a huge amount of outside air.

[rickdesilva]

Try the marker light over the driver window.

[dale farley]

I wonder how much air pressure/volume you actually need to locate a leak by pressurizing the inside of the bus and using soap to find the leak? I tired it one time with a large vacuum cleaner (using the output of the air), and that didn't work.

[Gil_J]

Dale,

It takes a lot. You have to overcome the natural leaks and then have enough pressure to pressurized the leaks, many of which can be real small. It's important to seal all natural vents, like the fresh air intake for the dash air. I know the blower that Prevost uses is huge!

[dale farley]

I wonder if there is any type fan other than one made for this purpose that would work?

[Joe Camper]

Sure Dale what prevo uses is a blower out of a residential fan forced gas furnace. Mounted on a tall dolly so it can be rolled up to the drivers window Then sealed up with a soft thick foam gasket.

Do u haul trash to the dump ever people replacing furnaces all the time. Or keep your eyes open for a discarded furnace at the curb and pull the blower. I have a couple in my garage for fans they crank they r quiet and they were free.

[JIM KELLER]

I have watched this leak detection system used at Prevost. The blower is crude and made in their shop but works great. Like Joe said, they roll it up to the drivers window and turn it on. Spray the Bus with a soapy solution from a two gallon tank sprayer and watch the bubbles appear. When finished the Bus is all ready for a wash job !

[JIM KELLER]

We have a non-slide 2001 royale. There is a water leak which presents itself in the window treatments behind the drivers seat and back to the galley. We have resealed the horizontal seam on the roof on that side, but after the last rain, the window treatments were soaked again. We would appreciate all suggestions. He cannot SEE where the water is coming from. Thanks

Any update on this Post ? Resolutions of problems help all Members.

[dale farley]

Thanks Joe. I'll start watching for a blower unit.

[Mikee]

You may want to check the awning mounts for being loose. I have found several where the awning mounts were the issue.

Mikee

[JIM KELLER]

AMIGOMILLERS, Keep us updated on this water leak so we can all learn and help each other.

[rdkpotter]

Unfortunately I have that same water leak on the window treatments in my 02 Royale. I've tried sealing everything I could above that second window drivers side but to no avail. Thought I had it fixed but while in an rv park yesterday in a big downpour, the leak is back - with a vengeance. Likely the roof A/C seal as suggested above. I'm going over to Prevost Ft Worth and have them do their leak check. Thanks for all the input.

Rich Potter
2002 Royale
2014 Grand Cherokee

[Robert Freeland]

I have the same exact leak (behind drivers seat) in my 01 Marathon - no roof a/c. I just bought this thing last month and spent a ton fixing it up and on our first rainy night with the kids, this happens!? We were planning on going cross country and now have to turn back. Sooo frustrating. Is this a common problem with Prevosts?

Could anyone please recommend a shop in California that would do a good job sealing the whole roof? Wanna make sure this doesn’t happen again.

I called Prevost in Mira Loma and they’re booked out for weeks.

Any help would be greatly appreciated. Thanks

[Travelingman]

Talk with Jim Purcell at CoachPro LLC in Oregon. Jim sanded and sealed the roof of the Marathon XLV I just bought with EDPM two part epoxy roof coating. The specs on it are pretty dare good. I have also seen where folks spray their roofs with white bedliner. Everything has to come off to do the job right. Maybe a trip to Oregon is what the doctor would order;-).

[Gil_J]

Robert,

There are few places for the leak to originate. So, it should be a job and competent RV place can handle that works on any high end RVs.

Your coach should have a one piece aluminum roof with a perimeter rivet line and possible a rivet line in a couple of feet from the front and back. All caulk joints need periodic inspections and resealing. I'd pay particular attention to the front cap to roof seam.

Of course, there will the converter made penetrations. Some will install an extended trim on the roof the length of coach. Your awning mounts are another must inspect location.

Resealing penetrations is not a big job, certainly not big enough to disrupt your trip. Doing a roof coat will take a little more time, but not a lot.

[Dtjoint]

Roof leaks of this type are a common Problems in the GMC motorhome community. These, too, are metal (aluminum in that case) monocoque structures with the external aluminum panels glued to the stringers. The common leak points are the seam between the front and rear caps and the roof panels, the seam between the side panels and the roof panels, the clearance lights, the roof pod, roof rails and ladder mount and the awning mount points. The solution requires removing the 40+ year old sealants, cleaning well and resealing with a self leveling polyurethane caulk. Never use silicones as the bond between the silicone and the painted metal panels can release as soon as the UV light hits the silicone allowing water to flow under the silicone even though it looks fine.

while we had no active leaks when we purchased our XL, there were signs of previous leaks. We had the roof recaulked with polyurethane and then had the whole roof coated with a white elastomeric roof coating similar to what is used on commercial buildings. The elastomeric provides a positive water seal while also keeping the interior cooler and quieter. From the ground you cannot see the white coating on the roof. Total cost was $750 with someone else doing the work (I don’t go on the roof anymore)! The materials can be purchased on line, at many big box stores or at commercial roofing suppliers.

[Dtjoint]

One more thing. A blower is also used to find leaks on GMC Motorhomes. There the blower is mounted to the drivers side window and tape used to block all the vent openings to pressurize the interior enough for soap solution applied to the outside to bubble at the leak points. Often the rubber seals around the windows will bubble the soap solution even if there is no apparent water leak there. In that community it is really hard to observe the path of the water so where it comes inside may have little to do with where the leak actually originates. So, with something as large as our Prevost coaches I think it will be really hard to find the actual source of the leak. A careful reseal seems to me to be the only successful way to deal with water intrusion. After 20 years of flexing there are just too many places where the water actually enters.