Never :)

There are 3 gaskets, 2 small ones that cover the hinge hole and the larger one that goes around the door. The small ones can be replaced only if the door comes off the body, not a simple task because of the weight. The large gasket is easier, but the rear panel will need to be removed.

I suspect that the gaskets may be dried out, so spray on some vinyl protectant on them to make them softer. Then use paste wax and wax all of the metal around the hatch, including the hatch itself; that will also keep rust from forming.

If the large gasket is torn, it will need replacement. If it is loose, glue it down with gasket adhesive.

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)