I just finished repairing the rear bumper on my 85 300D. I accidentally bumped into the pillar on the side of our garage door and the bumper just fell off
As usual, the bottom aluminum channel on both sides was no longer there - totally corroded away. But the top one was still sound. There was some quite deep pitting in several areas inside the bumper. The rubber inserts were not perfect, but I reused them. Outside of bumper is good. One bumper shock had in past been collapsed, but I couldn't get it to release and almost destroyed it trying!
What I did, was
- remove brackets from car
- paint the pitted areas of bumper interior and the steel brackets with POR-15.
- make a cardboard template from the rubber inserts and the square steel end of the brackets.
- Using template, drilled two 1/8" pilot holes through bumper on lower side
- Temporarily installed the brackets onto the bumper along with rubber inserts
- using pilot holes as guide drilled holes through the steel bracket flange.
- Removed brackets and enlarged holes to 9/32"
- Enlarged holes in bumper to 9/32" and then used small file to make them square.
- Bolted brackets and inserts to bumper using 1 1/2" long 1/4" stainless steel carriage bolts.
- Applied some 3M 5200 adhesive between the rubber insert and the bumper for good measure
. Also used the sealant to encase the bare edges of the steel brackets in hope that this will prevent salt penetration.
- Reinstalled bumper.
That seems like a lot of words. Perhaps I should have just said that I repaired using a pair of S/S carriage bolts on each side to replace the lower channel
Hardly noticeable.