When someone says the heads were 'done' at xxxxx miles do they mean the
head gaskets were renewed, or that the heads were replaced, or that they
were simply tightened up?

My 1984 Caravelle GL (183k miles) had a recon engine in 1991 which has now
done 76k miles. I put a new expansion tank pressure cap on, and now there
is always a bit of air in the tank which is never purged. Also the engine
is sounding more like my previous air-cooled. Does this indicate leaking
heads?

Is there _preventative_ maintenance one should do on the heads, or can you
only wait until there is a disaster?

Lionel Tun
lionel@ark.prestel.co.uk