[Bob Meadows]

After purchasing my car (F Reg. 240) I removed all the rear bumpers to Waxoyl- this included the two support bars that pass the bodywork (scaffolding springs to mind!) these had also been separated from the bumper aluminum section treated and put back with gaskets between the steel & aluminum:~ I think that one of the reasons the rear section are prone to rust is that the water runs down the tailgate and through the gap between the trim section & boot.
The design here encourages the water to sit or pool on the metal lip section hidden under the rear bumper (Also pointed out in the repair article)
How to resolve? Once the underside of metal work is free of rust then thoroughly Waxoyl or treat with your favorite product out & inner bodywork.
Under the black bumper i.e. The part that would normally rest on top of the aluminum support rail slide insert short lengths of plastic approximately 1/8” thick. This will raise the black bumper clear of the under rail just slightly - install the plastic with gaps that will enable water to run away freely should it collect.
The outer trim section- normally stainless or all black is drilled at each end and the center- this is screwed directly into the bumper section i.e. through the black cover & aluminum under rail.
I used small stainless flanged self-tapping screws that do not look that out of place.
The outer edge of the trim section should be sealed against the bumper- you can use self-adhesive “E” draught excluder here.
The next part that has to be sealed is the small gap between the bodywork (just under the tailgate) and the screwed down trim section- Windscreen sealer is ideal here as it remains flexible but can be neatly finished.
The result is an area that transfers water run off down the tailgate and over the top of the bumper rather that under it and down the hidden parts of the body work.
The trim section is still removable after the screws have been taken out and the sealer is easily cleaned off & replaced.
Trust it helps.
Bob.