The Cessna 120-140 Association Forum

I just got plane back from annual. Had the gasket changed for oil seeps that seemed to show up on the side of reservoir.
However now there is an obvious leak at the rear of the tank from the gasket, middle of flange right above the alternator.
This leak was not there before. I have looked for the proper torque for the 6 ( I think) bolts , I can’t find those on the usual searches. Any suggestions on a securing technique to get this leaking gasket to stop with proper torque values maybe?

This is pretty common. It's exacerbated by folks cranking down on the nuts in an attempt to stop the leak, which leads to a warped flange, and more leaking. To make things worse, the tanks are prone to cracking at the weld to the flange and it's hard to tell exactly where the oil is coming from with all the air swirling around under the cowl.

They are 1/4-28 nuts so the prescribed torque is 75-85 in-lbs (C-series overhaul manual, page 119), but that's assuming a fiber gasket. Those silicon-rubber gaskets are pretty compressible, so you're sort of on your own.