Replacing water heater on old vans

[fwdanielson]

It's time to replace the water heater on our 1995 Chevy based Roadterk. The mechanics of it are pretty straightforward but I'm a bit unsure how they sealed it on the outside. The sides are curved in the old American vans so even though the top of the mounting flange is flush, there is a pretty good gap at the bottom. The gap is filled with some kind of sealer, probably just a thick bead of butyl sealant.

Has anyone replaced a heater on a curved side van? I'd like to do as good of a job Ealing it up as they did at the factory.

[RT-NY]

I have the same question for my 1999 Roadtrek 170. The mounting frame is very well sealed all around in the gaps to the curved surface of the van -- it looks to me more like a custom gasket than an applied liquid sealant. I would also be interested to hear from anyone who replaced the water heater on these older Roadtreks.

[fwdanielson]

Here's a couple of pictures showing how the gap increases towards the bottom and how it spans the ridge in the side of the van along the way. I was a bitt surprised when measuring to find that the gap iat the bottom is a full 3/4 of an inch.

The seal is definitely hard and looks like it was tooled so it seems to have been at least somewhat soft during the install. Definitely not a compressible material like some sort of weatherstrip.

[RT-NY]

My 1999 RT looks the same, and I am planning on doing this job this summer, so perhaps we can compare notes.

Someone did ask this question once on this forum and butyl tape was recommened:

https://www.classbforum.com/forums/f...oor-10908.html

But that looks to me that it will not be thick enough to fill the gap. Do you think that a sealant like this would work?

https://www.homedepot.com/p/DAP-Poly...8816/205030319

Or perhaps something like this in two layers?

https://www.amazon.com/Sealant-PROMO.../dp/B07CTQ67X9

[booster]

Originally Posted by RT-NY

My 1999 RT looks the same, and I am planning on doing this job this summer, so perhaps we can compare notes.

Someone did ask this question once on this forum and butyl tape was recommened:

https://www.classbforum.com/forums/f...oor-10908.html

But that looks to me that it will not be thick enough to fill the gap. Do you think that a sealant like this would work?

https://www.homedepot.com/p/DAP-Poly...8816/205030319

Or perhaps something like this in two layers?

https://www.amazon.com/Sealant-PROMO.../dp/B07CTQ67X9

I think you are on the right track with those products.


I used similar in my recent rear side window fix on our 07 Roadtrek 190P to take care of a very similar body curvature vs window issue. I had about 1/2" to fill in one corner.


In my case I had some 3/8" of the rope butyl rope around here from past project, but it wasn't enough to fill the whole gap. I put a second layer on by stretching the rope out to get the right thickness, including being able to taper it down to the small blend area where it wasn't needed. You need to be pretty careful about thickness as the stuff doesn't compress as easily as you would guess by squeezing it. You need to taper the first layer also so they don't get any gaps between the layers. I did leave the butyl in further than the edge of the window frame by a little bit as I knew the butyl would not be able to be smoothed out well enough for appearance.


I then used urethane caulking to go over the top of the butyl and all around the rest of the window in varying bead widths to smooth it all out. It actually came out looking surprising almost unnoticeable that the the window has varying seal thickness around it.


I used this urethane caulk, but what you list probably would work also. A lot depends on the viscosity of the caulk, and the stuff I got was just the way I liked it for getting smooth.


https://www.homedepot.com/p/Loctite-...5273/203163733


There is a thread on this forum about the whole adventure. I think I may have inadvertently called it urethane rope on that thread. I think you can get both these days, but when I got this it was only butyl.

[hbn7hj]

Looking at mine, a 2003 Chevy Express, they put a slight arc in the water heater frame to minimize the gap.

[fwdanielson]

Started pulling the water heater today. The sealant from the factory was definitely not butyl tape. It was originally white and just stained black around the edges. It is still malleable and feels more like plumbers putty or glazing compound than any type of caulk or rubber. You can pull of a chunk and mold it like stiff clay.

Another interesting bit is the construction. There is a square wood frame to which the water heater is attached with wood screws. The van sheet metal appears to riveted to the wood frame. Not sure how that was done. The opening s 12 3/4 inches square which should fit the new heater ratherr well and I should be able to just screw in to the wood frame and not have to make a screw holes in the van sheet metal.

[GallenH]

I had to remove the outer frame to the water heater on my 1997 PW a while back to replace the expansion valve. Similar gap at bottom where body curves inward. "Black gasket" around frame was also (originally) white putty-ish material that had darkened with exposure to the weather. Must have been a common practice among manufacturers.

[fwdanielson]

Originally Posted by GallenH

I had to remove the outer frame to the water heater on my 1997 PW a while back to replace the expansion valve. Similar gap at bottom where body curves inward. "Black gasket" around frame was also (originally) white putty-ish material that had darkened with exposure to the weather. Must have been a common practice among manufacturers.

What did you use to seal it when reinstalling the door? How did it work? I'm leaning towards using Sikaflex or similar polyurethane caulk.