R fuel tank

[58-172]

I have a 58, C172 that has been converted to tailwheel. The last couple of flights I have notcied that after I land and walk around, The right trailing edge has a little fuel on it. Not really enough to drip to the ground but it appears to be leaking. You can't see any leaking in flight. Wipe it all off and come back the next day and there is nothng there. I have checked around the fuel cap and sending unit just behind it. The sending unit appeared to be a little damp. I stuffed part of a paper rag over the sending unit, under the cover. Flew it for an hour, the rag had some blue spotting. Not enough the run back to the trailing edge. I don't think anyway.

It is hangered unless flying. Didn't know if anyone has had such a problem or not.

Any body have any idea's ???

Thanks
Kirk

[canav8]

Kirk, unfortunately, you will need to pull the tank wing cover off and have a look. These tanks do not normally leak unless the tank has had some corrosion causing the wall to be compromised or the seals to the tank are worn. Either way, you will have to pull the tank to see what is going on.

[c170b53]

Sounds like you should change the gasket on your sending unit to start if you have confirmed the fuel is not coming from the filler neck, forward of you sending unit. Is it more pronounced if the tank is full? Or less so if half full?

[hilltop170]

Before you start removing pieces of the tank, carefully torque each screw on each tank penetration flange. Sometimes cork or even elastomer gaskets start to leak because the gasket has relaxed a little relieving the seal. By "carefully torque" I mean gently apply torque with a screwdriver to each screw going back and forth across the flange, not around the flange one after the other. If any are loose, don't tighten more than 1/4 turn. You don't want to mash out the gasket by tightening too much. After checking each screw on all the flanges, go out and duplicate the conditions where you noticed the leak.

Also, check the rubber hoses on the vent hose on top of top of the tank and fuel lines to the engine. They could be/probably are very old and may be cracked. You can try the same "carefully torque" procedure on the hose clamps first and see if it helps before you start replacing things.

If the above stops the leak, you then need to decide if you need to replace the offending items.