Saturday, July 18, 2015

Trunk Hinge Repair

1967 Ford Mustang Fastback trunk hinge repair While stripping the trunk, I noticed that the drivers' side trunk hinge had a side-to-side wobble that the passenger side did not. Upon further investigation, I discovered the lateral support that locates the hinge mount had been sheared off.

My guess is that little rear end fender bender from the original owner is the cause. The trunk lid got shoved forward a little and the two spot welds that hold the hinge mount to the support were the weak link that let go. This was not on my list of stuff to fix.

Easy enough, I guess, once you can reach everything and clean everything.

The broken support (on the left here) and the hinge mount.


Close up view reveals two spot welds that are torn, allowing all that unflattering 'jiggle' in the trunk hinge. Some folks dig a little jiggle in the trunk (that's not funny), but this I have a welder handy, so why not? I need to clean it all up, correctly locate the pieces together and plug weld them back into a happy union.


First thing I did was to drill two witness holes through the hinge and the mount so I know how to line them back up later. I've already done the same thing with the door hinges. Notice that fastbacks come with coiled springs instead of tension rods, which you'll find on coupes and convertibles.

Hinge is held in by two captive nuts. And a better view of the sorry state of affairs.

 Removed the hinge, pulled the support forward for access and cleaned it all with wire wheels. The support bent easily out of the way.


Clean the backside of the support. 


I always seem to miss a shot in this process - here, I'm failing to show the two 1/4" holes drilled in the hinge mount for the plug welds (fake spot welds). You can see one of them between the vice grip tongs. Clamp tight, and bring the heat!


 Here's the plug-welded repair. Keep that ground clamp close and make the metal "surgically clean" before welding. That's my best welding secret so far. Oh, and welding sparks will go right through cotton tube socks like they aren't even there, and that hurts.


Checking proper alignment with the Dangle-ometer. Angle signs are reversed from passenger to drivers side, but the numbers match. Another Communist Freight special. Be sure to get one where the magnet is flush to the base. Quality control can be hit/miss with those guys.



Anything worth doing is worth overdoing. You can see where the two plug welds have penetrated (the heat discoloration spots). I decided to add a couple quick tack welds to the backside where the original spot welds were torn up - because I had the welder out already, so why not? I consider these extra credit welds.


Trunk hinge now properly located where it should be.

Welding advice:
1. Surgically clean metal - seriously, make it clean. No dirt/rust/weld-thru primer. If you're gonna MIG weld it, clean it one more time.
2. Welder settings - this one was easy, set the Millermatic to 18 gauge and hit it. These were vertical welds, and they didn't really give me any issues. Start at the center, then hit the top of the hole, then walk the weld puddle side-to-side on the way down.
3. Keep the ground clamp close to the work. This makes a bigger difference than some may think.
4. It's OK to whimper a little when you burn yourself as long as no one else sees or hears you. But otherwise, you have to suck it up and make a manly "Arrgggg...." sound.

More to come. Up next is the front fenders getting torn down and patching/priming, and then we're onto the really big project - the full frame rail assembly replacement!

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