Q: How can I tell if a trailer has leaks?
There is a well proven saying – “All Airstreams leak”. It usually shows as a wet floor somewhere around the perimeter of the inside when it rains. A leak may occur at, say a vent, it will run down between the skins and into the C channel on the floor and then emerge onto the floor at a gap in the C channel many feet away. As you can see, where the leak appears, and where it really is, may be two different things.

Q: How can I really pin down the source of a leak?
Get an assistant and station them inside the trailer where they can watch for the first appearance of leakage. Squirt a garden hose on the suspected areas starting down low and finishing high. Use direct spray on suspect spots. Often this gets fast and definitive results, but in borderline cases could take five minutes. Inspect the exterior area closely, looking for any breach in the sealant. This usually works the best with the inside skins panels removed during restoration.

Q: What is the source of some common leaks?
On 7 panel endcap and later trailers, rarely is it the skin panel seams unless there has been a prior repair or damage. On the older trailers, especially the 13 panels, the end caps are prone to leak. Most other sources are:

  1. Doors. The source can be the door gasket or a badly fitting door. Also, it can be lack of proper caulking of the gutter over the top of the door. Inspect windows adjacent to the door.
  2. Roof Vents. All vents are made by cutting a square hole in the roof. Then an upstanding collar is riveted to the roof. This joint is prone to leak about every ten years. Carefully scrape away old caulking and apply new. Look for loose rivets. Never use screws here. Note that the water can fall onto the ceiling inner panel and run in any direction before appearing.
  3. Vent pipes and small fittings. Make sure the sealant is not brittle and dried out.
  4. Windows. Sealant is required on the upper seams, and the gaskets and seals must be maintained.
  5. Air-conditioners. Remove them and check the lip and opening they cover up. Also check the attachment holes. Use sealant to re-install the fasteners. This also a good time to clean the AC, as this will improve its efficiency greatly.
  6. All the shrouds on the sides. Make sure all the mating seam sealant is in good condition.
  7. Rear bumper. This is a big one for trailers where the bumper box is attached to the rear of the trailer or the frame channels continue past the end of the trailer shell. Water comes down the back of the trailer and is diverted by these horizontal surfaces right into the wood floor. Seal this juncture well with sealant.
  8. Screws into the skin. Previous owners are notorious for adding things with self-tapping screws – and they will all leak. Always use a dab of Vulkem (polyurethane) sealant on any rivet or screw you install.

Q: What type of sealant should I use?
Depends on where it is being used. The most common sealant is a material called Vulkem 636 polyurethane sealant, made by Tremco, and is still used by Airstream in places. You will occasionally find Vulkem 116 in Home Centers and Hardware stores. It is a textured sealant, and is not the same, but works just fine in wheel-wells, belly-skins and frame areas. The 6xx series Vulkem products are marketed by Tremco to the manufacturing industry (like vehicle construction) and the 1xx series Vulkem products are marketed to the construction trades (like masons). The difference in numbering is for inventory tracking purposes. Vintage Trailer Supply is a good source.

Q: What do I do with the sealant tube once I open it up? It always turns hard or plugs up the end.
When done using the tube, put a baggie over the end and throw it in the freezer. Take it out next time and allow to thaw an hour or so. Throw it back in again when done. You can go on forever doing this until it is used all up.

Q: How do I get the fine bead in the seam edges?
Use a small syringe. (Vintage Trailer Supply, veterinarians & woodworking suppliers). It will apply a perfect 1/8” bead. Use Mineral Spirits to clean any messes. Store your filled syringe in the freezer too.

Q: We can move the shell of our trailer slightly up and down near the tongue, and the frame tips are just starting to wear through the sides of the belly skin in places. What can be causing this?
The bolts that hold the shell to the floor do not pass through the chassis frame members. The plywood floor and flooring is installed on the chassis before the shell is secured to the floor. The perimeter U channel is bolted to the plywood with 1/4″ bolts which are bent over underneath the floor. Additional sheet metal screws are used to secure the channel into the floor. The belly skin is then wrapped up from the bottom and secured to the U Channel with rivets. In the 1950’s, the belly skin is actually crimped over into the C Channel. The upper skin is then attached to the U Channel with rivets and covered with a trim strip. Depending on the year & model, there can be two small angles at the inside center front and rear that tie the skin to the floor.
As you can see, water damage and floor rot can cause the trailer shell to become loose from the chassis, and is why it is very important to repair the floor and to prevent any future leaks.

Q: what’s the best way to prevent leaks and leak damage??
Store the trailer in a barn or under a carport.