there is a BMW cross ref. cap that works, I used it on my '82.
Unfortunately it does not have any codes or makers marks, just "zu"
and "auf" arrows and a warning in german about cap removal ( I think).

and the number "100"

maybe this helps? :)

Alistair

On 23-Aug-09, at 1:29 PM, Alan Felder wrote:

Ok, I've been surfing the net for several hours now for a replacement
expansion tank cap (metal) for my 82 diesel westy.  None of the usual
suspects seem to have them, nor the scads of other sources.  Anyone
have a
clue where these might be found?  They are NLA.

--
Alan Felder
Austin TX
82 Diesel Westy