Greg, those green O-rings go around the periphery of the cast iron
cylinder, where it fits into the aluminum head.  The "small" refers
to their thickness, not their diameter.  You can look at them by
taking the heads off.  Believe me, you'd much rather it was the cap,
but by the sound of it it's probably not.
:-/
David

At 08:29 PM 9/28/2008, Greg Baxter wrote:
>crackles, but mostly pops. Likely not coincidentally, following these
>pops, I end up with the coolant light on after a long run of this engine
>braking. My guess is that the pops are a result of the air that is being
>sucked in (?) and eventually displacing the coolant in the expansion
>tank. These small green o-rings - what does Mr. Bentley call them? I'd
>like to take a look and get an idea of what I'm looking at here.

--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage," '85 GL "Poor Relation"