I have a dragster and the info is found on page 19 from the manual:
Some of us have the expansion bottle with the ROUND brass insert.
in this pic
Hence more info (and caveat):
Wrenching ONLY when COLD and retorquing with the indicated 8 Nm value.
but not like some frenzied neanderthal on stero´ds.
Otherwise you'll kill the brass insert!
It will turn in the thin plastic wall of the tank and your screw will be useless.
And getting a new one might take a long time nowaday.