The fuel leak in my left wing tank that I thought I had fixed a year ago has returned.  I have tanks in each outer wing panel, 12 1/2 gal, and after 14 years the gasket that secures the sender units to the tank developed a very minor leak, just enough to require fixing.  Last year I removed the wing, pulled the fuel sender assembly, installed a new gasket and re-installed the sender unit.  Unfortunately the threads in the 1/8" mounting plate stripped in one of the five holes. I tried threaded inserts but they would not fit tight enough to prevent rotation.  I installed heli-coil inserts and the fix was marginal so I added sealant around the bolt heads and that seemed to work.  Well, one year later and the leak is back. Here is a photo from last year. The patch you see on the tank is from 15 years ago to repair a leak after the first fill.  It is the sender unit / gasket / mount plate that is the problem.  I'd like the break the pencil of the engineer that designed an 1/8" mounting plate.

After the Gathering I will pull the wing again and attempt a permanent repair.  Problem?  What will be a good fix? I could rotate the sender slightly and drill 5 new holes and thread but an 1/8" mount was a crappy method the first time.  No access to inside of tank.  Here is a VERY ROUGH line drawing of the setup. Excuse my total lack of artistic talent and lack of motivation to improve it.

I'm considering having a friend make up a matching aluminum puck approx 1/2" thick, drill and thread mount holes that do not penetrate to the tank, then epoxy or J.B. Weld the puck to the existing tank mount.   That would give excellent mounting pressure for the gasket and the only hole to seal would be the center hole where the sensor probe enters the tank.  I'm not inclined to cut the old mount from the tank and start over without having access to the inside of the tank and I'm not inclined to open up the tank.  I'm convinced I could get a good seal on the puck, especially with a lip / joggle turned on the puck on the tank side and then covered with several layers of glass / epoxy.  I'm liking this fix better the longer I consider it and making mental adjustments.


Larry Flesner
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