My frame member was bad enough that I really though I would have to replace the entire striker panel. But once I got it all apart and took a good look at the load paths on the failed system and those that this repair would present, I decided that this was a much less risky and less expensive solution. Truthfully, I really didn't like the idea of cutting through the frame member face to remove the section that the new complete striker panel replaces. Nor the price tag for it and all of the rivets. So I decided that a hybrid repair that combines replacing the perch and adding the reinforcement would be the way to go. The perch was about $75 and the reinforcement $15, both from the dealer. The striker panel would have been about $460. Never mind all the rivets...
I've attached some photos. The first is of the failure as I discovered it (with spring removed). The second and third with the area all cleaned up. The fourth is ready to install the perch and reinforcement. The fifth is ready to weld the reinforcement to the perch.
You'll notice that the majority of the rust on mine is actually in the open field beneath the replacement where there are virtually no structural reactions. It was also clear at this point that all but one rivet would be in completely unaffected steel.
Once I had ground everything down I applied a phosphoric acid rust conversion/inhibitor solution called Ospho, made by Skyko. I also fashioned a bent tube that fit on a large syringe body so that I could apply the same solution inside the cavity through the small area of rust-through. I put a little mesh and body filler there just to keep water out. Once everything was primed (I primed the perch both sides separately) I fitted the new perch.
Initially, I thought that I needed to make the rivet hole a little larger than 1/4" because I was having a hard time getting the rivets in. The I figured out that I could use a 3/8" drive deep well socket to tap them in. Socket size doesn't matter since you put it on the rivet backwards (drive side toward the work piece) and tap it in with a hammer. Nice tight fit. The countersunk rivets were a bit of a challenge but worked out fine. Be patient.
The countersunk rivets are Klik-Lok SC88KL Structural Rivet from Fastenal. $.60/each. The other rivets are Klik-Lok SB8EKL Structural Rivet, also from Fastenall. They are $.63 each. I think MB wanted $3.75 for those...
Once the perch was in place I started fitting the reinforcement atop it. Since I'm not a terribly skilled welder I used the old perch that I had removed to practice on. Afterall, it should be the same alloy and is similar in thickness. So it was perfect for dialing in my little old Craftsman MIG welder.
With the new perch and the reinforcement in I primed it all once more, added a coat of heavy body seam sealer (see install instructions about where NOT to put sealer), applied a rubberized & paintable undercoat, and then sprayed a couple of coats of automotive paint - closest color I could find off the shelf at the local AutoZone.
Links to rivets:
Products | Fastenal
Products | Fastenal
Spring Compresor:
Mercedes Coil Spring Compressor Suspension Tool Kit Set | eBay
Pneumatic Rivet Tool:
1/4" Air Hydraulic Riveter
Will post the repair instructions shortly.