Stand by, I’m finishing up over 50 pics on this project for you…. be right back…
OK, as anyone who has owned a GMC before…. water leaks is an always present danger. And it’s not because the last owner screwed something up, termites or anything like that…. to be quite honest the biggest weak cause is time. Tinme is THE #1 killer for everything and I mean everything. We only last so long and there IS NO warranty on that.
The GMC Motorhome body is truly unique to any other vehicle out there…. designed like and aircraft body, the skin has expansion joints. Not obly does the suspension move to road, the loose ladder frame does too and of course connected to that via body pads the body also twists to the road. You need to be careful taking obtuse body twist situations…. if the elastomer rate of whatever sealant is on those body plates can’t move to the twist and stay adhered, pop goes that seal!
Old sealant, old shrunk gaskets and plastic parts no wonder we have to deal with leaks. Leaks to not occure through the aircraft grade aluminum roof…. it’s the penetrations.. the holes and the expansion plates. And you always need to stay vigilant. One GMC owner that really should not own one once got upset because a leak was repair and 2 months later it came back……. Immediately he blamed me….. I know the guy takes his coach off road and in places that are not level… and he popped the seam again… welcome to the world of GMC brother! Look, this is not McDonalds and you are not buying a 1/4 pounder with cheese…. the best you can hope for is someone that can help is willing to… so don’t be a jerk! Sorry, that slipped out,,,
Enough of that…. I need to have board shoulders in this business…. but what CAN be done on water leaks that truly will help?
Several weeks ago I put out a tip on resealing the top side rails…. did this project on John’s coach
Well over 1/2 of water leaks are at this rail We’ve beaten this rail thing to death, it that IS 60% of the leak possibilities lets talk a little on the other 40%.
That would be every other penetration. Take a look at the top of John’s coach looking back Yep, there used to be a roof pod up there and look at the frig roof and plumbing vents…… they are original! Lets look at the frig vent first. Oh man is there “gobbage” on these and the whole thing is gobbed together So making myself comfortable I set up shop to get that crap all outa there Step 1 is to get the vents off and all the fittings out. What sort of fittings….. rivets! Rats, you know the vents won’t last as long as the roof….. these were factory vents riveted on, they could care less about the guy having to replace it all … so it’s drill rivet time for me…
Next we place the new fixtures where as many of the holes are covered then tape off the area where the sealant will go. I mean look at the way the sealant was oozed out around the vents and they didn’t cover the entire seam on the second sealant go around. All installed, secured with self tapping washer screws. Before that, clean the surface, fill each old rivet hole with sealant and put a bead on the inside of the screw pattern . Now position the new vent where the new holes miss the old ones. Screw down with washer screws to spread out the pressure on the plastic.. well, the plumbing vents we use are metal but still, you may see some awesone new doodad plumbing stack that you may want…. it may be YOU who has to get that puppy up!
Also, taping off the area where the sealent will be… we know it will so why ooze it down like some erupting volcano A few more minutes and we can make it something like this With the trend going to blackout tops, using our kick-butt, German Bond-n-seal, this gives us adhesion and sealing between the vent and body then a sealant covering and protecting the screws and down to the outer edge and in an area you can bag off in the future to reseal when it’s needed. Hey…. NOTHING is forever! Ans oh look, the cover on the new low profile plastic vent cover covers most of the black sealaing itself And it ALL looks in place, even the sealant…..
Next gaping problem are the front and back top clearance lights. There are 10 of them up there (5 in front, 5 out back) which is at lease 30 penetrations water can get in. Yep, you wanna wear your water wings in the coach already!!!!! I mean what could be wrong with this There is no bulb socket, the screws are rusted off and the lens gasket is shrunk to failure in 1988. The lens have faded so far they look clear OFF with their heads….. yank out that butterfly bolt with a panel tool to reveal the holes below Print the pic above if you like and follow these tips. DO NOT PULL ON THOSE WIRES!!!!! The are connected each with a single bullet connection fron inside when it was manufactured. Any pull on that wire will unplg the connection and then life gets fun! Do what you want… you have been warned. How…… cut away the center wire from what’s left of the socket without moving it. the other wire (rear lights ti’s 12 volts hot and the rear is a ground…. keep that in mind). The second wire will be a bit longer but still… don’t pull on it. Hold the wire at the surface level with some needle nose pliers and strip off the insulation enough to crimp a red barrol to it. Di that with a 3″ piece of wire on it then stuff the wires down into the hole carefully. Oh look, you have hot wires and enough service wire to connect them nicely.
Next I smear a thin film of sealant on the gasket, a blob each over the 3 holes… bed down this big ole fat gasket….. sorry no, those are not available separately… These are 17 LED “Cats eye” duplicates of the original lights are $15 each. Hey look, if you like these buy them from me.. you might find something like them… cheaper, and you know they are… Hey, and check out the light pattern ours have 2 rows of forward LEDs horizontal with a bunch of LEDs facing up … who knows, you may need lights up there to land a UAV or something sealed and now beded down with seales in the screw holes, an awesome seal to the body, bond-n-seal on everything which is about all you can do with it ….and… you can take them off easily and replace them….again… NOTHING LASTS FOREVER. Yeah, they are LED but just trust me, they can fail too!
Next, there are front and rear seams on the roof running side to side, John’s seam has never been resealed BTWm the aluminum plate there is covering the old crank up antenna holes The plate gets a seam of Bond-N-Seal then with blind rivits… ever heads that one… blind rivet? Here is a regular rivet and a steel shank aluminum end capped aluminum rivet . You will need an air riveter… HF hasum…. with the steel shank that aluminum rivet is pulled to bond to the aluminum skin and with no hole in the back, no water will leak in. This is what you do with any hole 3/6″ or smaller. Drill it out and wack one of these puppy in and the hole is filled!
Taping off the front and rear seams off to keep it clean, I lay out a bead of Bond-N-Seal and level it out clean. I put enough on each side to get good adhesion . This material is also paintable so if John springs for paint he can clean and paint over it. So there we have it…. rails sealed, cross seams sealed, antenna gone and holes seald, clearand lights replaced and sealed and all the plumbing stacks and frig roof vent replace. Oh and there’s more penetrations but these are the biggies. Hos roof vents are gobbed too but look seaworthy, there are old pod holes, securing brackets for that solar panel, the antenna is really gobbed but probably at least will never leak So remember, you must stay vigilant on water leaks on a flexible vehicle body and don’t twist around so much…. Don’t gob the job, more sealant won’t do that much more and it looks like crap. Use materials others have found effective, this is too much a job to have an unexpected result. NEVER USE 3m 5200 on this project. You will destroy your coach to EVER get it off and nothing is forever, have the option to replace and reseal things as needed…. you will need to.
I have the sealant we use for $26 a tube, the work I did took 1 tube of black and most of a tube of white Bond-N-Seal… A roll of good masking tape… I use green to not pull off any old paint…. use rubber gloves, the stuff will have to wear off your fingers … ask me how I know, it’s doesn’t just rub off…. The vents are whatever you want to use, the LED lights are $15 each. Use what you want… good with me but for the work I do THIS is what I use. There are piles of new, space age things.. this is mine…….
Hope there was stuff in there that can help you, this is a process I have perfected over the decades of doing this… I make no arguments other may have contrasting views on some of this…. hey, isn’t it good we live in America…… Call me if I can help.
David Gardner says
That coach looks good outside your new place! Hope to hook up there someday myself 🙂
Wow, looks fantastic, can’t wait to see in person…
Dennis Hill says
Good article on roof sealant. Liked your pictures too.
The rail is that what runs most of the length of the rv like where a rain gutter is on other rvs ?
Yep, 60% of leaks come from there
I didn’t see anything above on that .are we to pull it off and caulk that to ?
Yep, do a search on the site for water leaks and you should find the stuff on that sealing process
Wally Anderson says
Thanks for showing metal plumbing vents. We are on our second set of plastic vents that crack probably due the curve of the roof. Switching to metal.
Yep… I mean plastic…. in the sun and rain all the time… what were they thinking…and then they were riveted in. No care in maintenance was considered…
Thanks for mentioning 3m 5200. I love that stuff and would have used it if you hadn’t explained why not to. Again, thank you.
Yes, for what it’s made for it’s great but don’t ever think you will get it off! Plus i’ts an adhesive not a sealant as much. I field that one all the time