Sunday, March 8, 2009

Welding In the Passenger Trunk Floor

Now that I've patched the quarter panel, I can weld in the passenger trunk floor panel and close it all up. The Weld & Sealant manual that I've been referencing during this project indicated a strange requirement not specified for any other panel I've replaced to this point. It specified the requirement for sealer between the wheel house and center panel and the trunk floor panel. I couldn't for the life of me determine how I was going to accomplish this without causing the sealer to flame up and burn away. So, I did what any good newbie does, I closed my eyes and did what I was told.

Here's the area ready to have the new trunk floor panel installed with sealer in the specified areas.

But wait! We can't just go welding a new panel in without preparing it first now can we? It's a tiny little panel as panels go so how hard could it be?

Well, first thing I noticed is that the flange that forms the gas tank opening seemed a bit too long. Did I get the wrong part? Was there something wrong with my car? I requested help on the VMF and was soon met with an answer from a kind gent who indicated that convertibles have an extra brace between the rear frame rails. I compared the old panel to the new one and... yeah, the difference is about the size of the conspicuous convertible reinforcement brace.

So I cut out the extraneous portion with the inclusion of some welding tabs and got back to business.

Done yet? Nope, not quite. There's a missing bracket to replace for the spare tire (plug weld holes drilled) and I just wouldn't be happy with the default black coating on the panel so I had to scuff it and prime it red oxide.

Ready now? Nope. Still have to drill dozens of plug weld holes along the frame rail, center panel, and trunk dropoff flanges. Only then would the panel earn my seal of mediocre standards. I can't live without my clecos these days so I made sure to apply them liberally.

Welds along the frame rail, the center panel transition, the drop-off, and the wheel house. Oh and the seam sealer added a whole new dimension of excitement. Fire! FIRE! Wierd though, the sealer expanded between the seams and filled the voids. PRO TIP: I'm not a pro but I did read the weld and sealant manual a little more carefully and it specified weldable spot weld sealer NOT seam sealer.... d'oh!

With the floor panel welded in place, it came time to replace the bumper reinforcement bracket. Ugly, rusty, bent-up thing that took one for the team when I removed it. I took my stainless steel wire cup brush to it followed up with some quality sand blaster cabinet time and finally some good old fashioned straightning up with a body hammer.

I ground down the welds and felt it a really bad idea to leave the freshly ground welds under the bracket without protection. I was in more of a welding mood than a priming mood so rather than spray the entire panel in a coat of DP74-LF, I opted to prime the bare welds under the bracket with weldable primer. I then welded the bracket to the floor and taillight panel. 

Update 7-23-2012: According to a discussion on the VMF, the bumper brackets must be welded through to the frame rail or, " If you only weld them to the floor, they will be so weak the slightest tap on the bumper will crush in the rear of the car".  Obviously, I did it wrong.  Hopefully I don't get rear-ended.

I made 4 plug welds around each hole in the taillight panel and ground them smooth.

Next, I ground down the plug welds on the trunk drop-off.

The new drop-off panel is actually a bit over-sized as you can see here... it has to be cut off flush with the quarter panel flange thus completing the replacement of the passenger side trunk floor. Now onto the driver side!


  1. Very helpful writeup AOLShove, I have to do a similar repair in the trunk area of my '68 Cougar.

  2. Cool! As you can see, it's not really a difficult job so don't be too intimidated. The worst part is cutting out the old panels. Good luck with your Cougar!

  3. Did you ever figure out what "weldable spot weld sealer" is?