[geo]

The one on my 412 was made of steel (only the pipe connections were
brass) and corroded rather badly (eventually leaking). I saw a local
(to Isleworth) 412 where the owner had had made a replica in
Stainless - a catering utensils company had made it for him at fairly
modest cost.

As to the 6-cylinder cars, I have wondered about this with a couple
of non-Bristols. It would be useful if someone with a better grip on
the chemistry could reply to this, but to my mind, with a non-sealed
system all the expansion bottle would be doing would be to collect
the coolant that expanded and with such a system, the coolant would
be exposed to the atmosphere and would still deteriorate at the same
fast rate. Those who know better, please give the true answer?

The last time I read an article on different types of
anti-freeze/coolant additive, the conclusion seemed to be that if one
used distilled water roughly 1:1 with a top-quality antifreeze in a
closed cooling system, then one might expect it to last far in excess
of 3 years. The further suggestion was that 100% antifreeze (if it
did not find weaknesses in the system) would exceed 5 years. Although
it was a good article in other ways, these final estimates were
somewhat lacking in evidential support, alas.

George