M4 210 fuel leak

[Roy]

I have a 65 model M4 210, that I completed a major over haul on both engine and airframe about 10 months ago. This airplane sat in a hanger for about 6 years before I got it and got it back in the air. Every since I have had it back in the air I have noticed a strong fuel smell at times. I have narrowed it down to the right side. Yesterday my A/P, A/I and good friend flew about a 200 mile round trip cross country. When he got back we could see blue stains running down from the gas cap area and it looked like we were getting some stain from the rivet line area in front of the spar.
We have swapped gas caps from left to right and problem stays with right.
I order a new set of caps from Maule and they don't fit.
Anybody got any suggestions?
Thanks in advance.

Roy

[maules.com]

If the leak is seaping from the wing bottom drain holes, and is blue staining around fuel cap area, most likely it is a crack in the tank, usually at the filler neck where a fuel nozzle has been hung. Cracks can also develop in the tank itself where it has expanded and contracted (deflated and inflated) due to blocked fuel vents. This is likely if it sat for 6 years and mud daubers or wasps got in there.

[Roy]

OK Jeremy, thanks. I looked at the wing yesterday and removing that tank looks like it could be quite a job. My A/I will be back in town this weekend so we might give it a try. Any good hints on getting the wing cover off that tank?
thanks
Roy

[maules.com]

Four tiny screws around filler, soak the tank cover screws with a penetrating oil well before attempting to get them out and replace with stainless. If removing the tank don't forget to retape the wingroots under the fairing. If old, maybe replace the two short rubber fuel lines at wing root while doing the job and refer to the service bulletin about over tightening the hose clamps.

[Roy]

OK, thanks for the tips. We will probably attempt to pull the tank this weekend.
Thanks Again.
Roy

[Roy]

Just wanted to let you know Jeremy you were right on the mark with my fuel leak. We pulled the tank this afternoon and there is a crack about 2 inches long right in front of the fuel spout neck. Mystery solved, now to get some fancy welding done and maybe be back in the air before long.
I continue to be very impressed with your knowledge about Maules.
Thanks again
Roy