Leak around fuel sender unit, possibly due to over-torqued sender plate

[Guest]

So, just when I think I'm down to fixing the final problems (for this season), my 80 GS1000G has a slow leak around the fuel sender unit which I just can't seem to stop. I've tried:

• Removing, cleaning around gaskets, and reinstalling
• Sealing gaskets with Permatex MotoSeal Ultimate gasket maker (fuel resistant, non-hardening), and letting cure 24h per the instructions
• Replacing both gaskets with new OEM
• Sealing new gaskets with Permatex MotoSeal, and let cure
• Beating my head against the workbench

I can see that the fuel is coming out around the sender unit gasket, so it's not the unit itself that is leaking (or pinholes in the tank). I've inspected the inside of the tank around the sender hole, and can't find any indications of rust, holes, etc.

For my final attempt, I've repeated the above, but added a thick layer of Permatex around the outside edge of the main (circular) gasket after the sender is installed. I'll let it cure for a week, then add the 2nd (half moon) gasket and re-test. But even if it holds, I'm not sure I trust it as a "fix".

The back-story is that it didn't used to leak. I'd removed the sender and petcock assemblies when I'd treated the tank with Evapo-Rust earlier this season. When I reassembled, I trusted my new(ish) 1/4 inch click-type torque wrench, but it failed me and I over-torqued. I can now see that the sender plate is slightly, but visibly warped. In all of the attempts above, I've been hand-tightening and guestimating the right amount of torque, really just aiming for consistency.

The warped sender cover leads me to believe that I'm wasting my time with the Permatex, and the only safe solution is to replace the sender unit. But I'm open to other suggestions. (And yes... it's time to invest in a better set of torque wrenches!)

 

[chuck hahn]

Is it from under the base plate itself or from under the leak tray cover thing? If you have the wrong length the screws on the drip cover you can accidentally poke through the tank wall. if its from the sender base plate I would apply a good coat of three bond 1207B on both side of the round gasket, assemble and let set overnight to cure. Then add the gas once cured.
Another place is the center hub the wires pass through on the base plate. Seal that up too.

Ideally you should replace the gasket.

 

[Guest]

Hi Chuck,

The leak tray cover thing is fine, the leak definitely seems to be coming through between the gasket and the round fuel sender plate. I should clarify that I've tried replacing the gasket, and adding a thin layer of Permatex 80062 (the red stuff), as well as trying a thicker layer of the Permatex MotoSeal.

Yeah, I was worried about whether my over-torquing the might have pierced the tank (though it wasn't all that much torque), but from what I can see through the bolt holes, and feel (from inside the tank), the tank itself seems to be fine. (I do have a pinhole leak about an inch away, but I've taken care of that with SteelStick).

I'll give the Three Bond 1207B a look if the MotoSeal doesn't do the job - thanks for the suggestion.

I've already started hunting around for a replacement sender unit, and I know some folks here have fabricated plates to just remove the sender entirely (though I'd rather keep the sender if at all possible, as it kinda-sorta works).

Thanks!
Chris

 

[chuck hahn]

Well, seeing its all out of sight on the bottom of the tank, maybe scrub the paint off with a wire wheel in a drill and smear some JB weld around the sender unit hole for an inch or two. This will for sure seal any micro holes in the area.

 

[Guest]

Thanks for the input, Chuck. I think the problem may be sorted. Hopefully this is my wrap-up post on this thread. For those who may find it later while searching for the same issue:

I cleaned and replaced the sender gasket, adding a thin layer of Permatex MotoSeal beneath the gasket (applied to both gasket and tank surface) following the directions on the tube. I then added a thicker layer of Permatex over the top of the gasket, and installed the sender unit, and torqued it down as consistently as I could without a (reliable) torque wrench. I could see that there was inconsistent pressure on the gasket in one part, due to my sender mounting plate being warped. So I applied another layer of Permatex around the outside of the gasket. Then I let the whole thing cure for 3 days. I suspect my failed attempts were due to a combination of insufficient curing time and possibly insufficient surface prep.

After all that, my tank has been sitting all morning, full of fuel, without any sign of a leak. If it does come back, based on Chuck's suggestion, and what I've read online, I'll try Three Bond 1207B instead (until I find another sender unit).

Thanks,
Chris