expansion tanks. why do they leak?What are they for?

[rob frink]

Earlier this year I noticed that the expansion tank on my windsor was leaking somewhere on the bottom around the thermostate tube.

I took it off, cleaned it, and resoldered to fix the leak. Now, a few months later it's leaking again.....from underneath...around the thero tube. At first I was dissapointed thinking that my repair failed...and began contemplating a new method to resolder the leak.

But, over the weekend at a local show, I looked at the other cobras and noticed most of them showed signs of leaking as well....in the same place. ...not as bad as mine....but the signs were there of dried green goo dripping/clinging to the lower thermostate tube under the tank.

Are these period looking expansion tanks prone to leak?

I'm thinking about making my own but a bit more robust.

I don't care as much for a period-looking appearance as I do for function....so what are they for anyway?


Anyone have a fix?

[StuM]

I have SPF 1580 and mine has leaked at the bottom of the overflow tank neck where it connects to the engine, since new. I can cut it down to a very small, periodic drip by tightening the attachment bolts, but need to be very careful not to over-torque. I've contemplated removing the whole thing and installing a new thicker, fluid-tight gasket, but it's so small an issue, I haven't done that yet.
Like you, when I look at other similar crs, I find all of them leaking to some extent. Guess it's just they way "God made 'em!"
Good luck.
StuM