Volvo: Thermostat, volvo s80 t6, volvo s80

Question
Volvo S80 T6 is in for 96000 mile service and Volvo recommend Thermostat change out at same time as timing belt replacement. Thermostat housing is noted by technician is cracked, why was there no temperature rise or loss of coolant prior to service?  

Answer
Stefan,
Two things come to mind, first it may have had a small crack in the housing that when it was pulled off the tech was of the feeling that it would not seal up again. Or secondly as the t/stat was being installed it cracked. Maybe a small crack and slight leak were not seen and there was a small amount of coolant loss only not enough to cause temps to rise. Just a lucky thing to find the crack before things got worse.