A project post! These will become more frequent (and come with more photos) as winter approaches and the bus is taken offline due to salty roads. This particular project began a few months ago, after I crawled around under the bus trying to find areas of rust overlooked during her purchase inspection. I didn’t find much and that made me happy, but did notice the seal was no longer in place around the holes through which the drains for the icebox/sink unit come through the floor. All I could envision was a lot of water heading into nooks and crannies and rusting the body from the inside out!
Sealing the holes following the Bentley manual is pretty straightforward. My problem emanated from a plate (not mentioned in Bentley, but it is original) installed around the drains. While the sheet rubber usually installed to seal this area would prevent water from splashing up around the drains, it is not thick enough to seal the gaps (white arrows) between the bus underbelly and plate.
To solve this issue, I settled on closed-cell foam (actually a cheap camping sleep pad) which solved the water retention and flexibility issues and was thick enough to fill the gaps. Using the plate as a pattern, I traced and then cut a matching rectangle from the sleeping pad. Using a new razor blade is a must for the cutting; dull blades will catch and pull the foam out of shape (I found an exact-o knife provided the best control, esp for curves). At this point, the thickness of the foam needed to be reduced.about a 1/4 inch. This was the trickiest cut, but with a square, small vice, and a little patience I was able to cut horizontally through the foam. Matching the foam to the plate once more, I traced the drain and screw holes on the foam and then cut them out. For the screw holes, an awl or ice pick is all you need to create the openings.
While the foam took care of the gaps between the underbelly and plate, it would not suffice to seal around the drain pipes. This was mostly due to the fact that the cap and wing nut where larger in diameter than the rest of the drain and the foam was not resistant to abrasion. In solving this issue, I returned to Bentley and the rubber seal. Found at any FLAPS, sheet gasket material is easy to work with, thin, and fairly tear and oil/fuel resistant (the cork stuff works great to replace old gas cap seals). Again using the plate as a pattern, I cut a rectangle from the gasket material and then traced the drain and screw holes. Instead of cutting out holes large enough for the drain pipes, I cut two holes (centered on my pattern) that were slightly smaller than the diameter of each drain pipe at the point where the installed seal would rest. Then I cut four straight lines (at 90 degree intervals) from the newly cut hole to the drain outline I drew. This allowed for the gasket material to slip over the cap, wing nut and pipe, but still retain a tight fit in its final position.
After gluing the gasket material to the foam using weather stripping adhesive, I installed the new seal along with the plate. Due to shadows, the black gasket material does not look like it seals tight around all side of each pipe, but it really does. The foam (blue) compressed slightly and filled the gaps between the plate and underbelly very well. The blue wire around each pipe holds the smaller drain in the center of the gasket because the water tank in the unit is a bit loose (you can see it is off center in the first picture).