Yes, Marshall nailed it. I use both a digital thermometer and a caliper so that I can measure both initial opening temperature and full-open temperature. Note that the full stroke specification is found in the Technical Data book, and not in the service manual (that I can see).

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC