Repairing Standing Seam on Car Underbody

Hello everyone,

"Some time ago, I accidentally bent the metal seam at the bottom where the underbody meets the rocker panel (likely by hitting something). Afterwards, I examined the bent seam with a friend, and he "repaired" it. Now, the overall appearance is similar to image #1 in the attachment (left = underbody panel, right = rocker panel). However, I believe this solution is rather sloppy because dirt and debris can accumulate in the bent metal. Therefore, I want to try to restore it to its original state (see image #2). Is this a good idea, and if so, what type of sealing material would be suitable to seal the gap between the two panels?"

Best regards,

cheeky

Hi,

"In my opinion, this makes sense because, as it is now, the moisture remains trapped in the lower sill panel. This will definitely lead to corrosion. However, I personally wouldn't seal it, but rather protect it with Sanders grease or Fluid Film/Perma-Film. This would keep the area open to allow any condensation draining from the sill to escape, as well as allowing for drying air to circulate."

Best regards from Berlin,
Olli.

As always, it depends. If the seam is already sealed from the factory, it would be sufficient to fill the "collection channel" with body sealant.
If it's not airtight, it should remain open at the bottom.

Hello!

Generally, sills have drainage holes for any condensation or rainwater that may accumulate. These holes are usually sufficient, so an additional drainage option is not necessary.

These stories at the bottom edge are often difficult to access. By sitting on them, the two sheets are separated, not the weld points, but any sealant present may tear, allowing water to enter.

Therefore, there is no longer any rust protection between the metal sheets, and rust usually starts from the inside.

My recommendation, based on my own experience, for resolving this issue.

Clean the metal sheet in the entire affected area and remove any loose sealant. The bent edge of the metal sheet isn't bad if it's properly sealed and there's no visible rust on the metal.

Warm the wood with a hot air blower to ensure that no moisture remains between the layers.

Prime any areas where paint is peeling, then seal with body sealant to ensure there's no way for water to penetrate. If possible, apply the sealant evenly to create a smooth, flat surface.

After that, treat the inner part of the wood. First, apply something like lanolin (oil), then follow with a generous amount of Mike Sanders grease that has been heated. After applying the grease, use a hot air blower to gently warm the wood, but not too hot, so that the wax can penetrate all the crevices. Also, apply the full treatment to the bottom, including Owatrol oil and, for example, rope grease.

Then you should have some rest for a while .

Best regards,

Peter.