[C320-list] Leaky fuel tank?

[Rick]

Mark, 
I replaced my tank a year ago because I had experienced a nasty sender leak over the winter from an overfilled tank and did not want to endure another fuel clean up mess over in the next several years given the age of my hull (20 years) when the tank could be expected to begin leaking.   My reasoning was  why wait for a fuel leak that day was predictable?
 
Based on my research of aluminum tank leaks across several manufacturers most diesel aluminum tanks can be expected to develop leaks within plus or minus 5 years of the 20th year.....a matter of not if, but when the tank can be expected to leak.  My review of the 320 discussion list pointed toward many 320 tank leaks occurring at the lowest portion of the tank's seam weld or the lowest portion of the wall nearest the tank's welded edge near the forward & portside corner area.

Did you see any evidence of fuel residue in the suspected area of the typical 320 tank leak? Have you considered pressurizing the tank with a small portion of fuel in the tank? Given the 320 discussion list tank leak details I observed, owners seem to report evidence of tanks weeping well before the leaks growing worse over time. 

When I received my new tank, the tank's fuel filler hose was securely sealed with a flexible cup like cover that was pushed onto the filler inlet that could also be clamped to that fitting. Also, all of valves were closed. When I opened a valve I could clearly hear the air pressure equalizing within the tank, suggesting that the tank was still under pressure when it left the factory, perhaps due to the temperature differences from when it was packed or the elevation differences from when & where I am located. This suggested to me that the variables involved in pressurizing the tank where tightly controlled by the tank's sealed valves and the filler pipe seal and that the tank was still under several PSI for a sustained time.  That is why I suggest attempting to replicate the tank weeping with a small amount of fuel in the tank for a period of time while the tank is left under pressure vs. simply looking for an air leak bubble with soapy water.
Rick
1995 320 hull #277



-----Original Message-----
From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Marek Fluder
Sent: Tuesday, June 21, 2016 9:30 PM
To: C320-List at Catalina320.com
Subject: [C320-list] Leaky fuel tank?

I have pulled my diesel tank today for inspection based on research on this list archive and my observations of diesel showing up in bilge area and around the tank. All fittings and sender unit on top were dry. Now I am puzzled as I pressure tested the tank spraying soapy water and nothing. The tank looks solid. Question to listers that replaced the tank - was the leak on the tank obvious?
I am stumped.
Marek
2005 #1028