Engine coolant temp one hundred seventy two degrees

172 is not even operating temp for good running engine . Per SE . Most thermostats are opening around 180. You're not they're yet!. Did you fill to B line warm up ! Let sit then inspect for water line at F mark???.

 

A Prius will eventually get to thermostat-opening temperature in steady cruising. But being a bit below thermostat-opening temperature after a night of taxi driving doesn't surprise me much.

 

No, it is still slightly cool. My 'normal' highway cruising temperature is 195 F. The radiator's electric fan doesn't turn on until about 203-205.

 

A night of taxi driving probably doesn't run the engine all the time or run it hard, so it's not surprising to have the temperature be lower than it would in continuous cruising.

 

Crap even running hard on SE 90 day cars cool running . It's gets hotter when I stop . Standing heat soak I guess.

 

Completely impossible to say. There are way too many variables in a hybrid that effect coolant temp.

The best way to gauge cooling system performance is steady state cruise on the highway. For example, my car runs 195.8f at anything over 60 mph. Large loads like bigger hills or heavy acceleration with lots of passengers spike the temp up. You can see the thermostat open more and the temp drop back down to 195.8 as more coolant sees airflow from the radiator.

Sustained higher temps then 195.8 or a longer time to return to that temp would better indicate cooling system performance.

 

Can you reword that ? I don't understand[/QUOTE]

if the temperature stays higher than 195 for longer than 5 minutes somethings wrong /

 

That.

If it stays higher you either have a weak pump, a stuck closed thermostat or other flow issues.

If you can't even reach and and/or maintain the thermostats set temp on the highway, you have one stuck open.

 

I use the Hybrid Assistant app on an old Android phone and my Bluetooth OBD2 reader while driving, and I am usually between 194-196 F. Uphill or heavy acceleration gets me around 199-201 F but almost immediately drops back down to about 195-196 F. I drive about 85% highway, as well.