Bob,

I'll have to spool up the FSM disc to see if it lists the "MM" of the wrench.

You'll want to be extra especially careful when you pull the sensor unit out
and disassemble it.It uses two very fragile wires to "sense" the level of the
float!

'About 1996 I managed to solder one of the wires back on a 240D.'Only
because my Scots... Irish... German... Grandmothers attended Mass on a
regular basis.

The sensing unit is inside an aluminum tube , which only adds to the likelyhood
of Algae buildup.

UPDATE: the FSM only lists tightening torque of 40 NM

REPLACE the gasket(s) when you do remove the sender.

MINE were plastic headed [and Rudolph, forgive me I used a GENTLE twist
from a pipe wrench to loosen them.]