Could be a bit of air in the system.
The reservoir is open to atmosphere.
Air in system can escape that way.
If worried about engine temp purchase a scan tool for more exact monitoring.

 

Picture helps.

 

Geez, if you're coolant is gurgling, you need to address that ASAP.
Radiator cap and thermostat..... I only recommend OE. Too many aftermarket parts just don't have any quality.

When engine is cold, meaning 8+ hours off, top off the radiator and recovery bottle and repeat every time cold until you address the issues.

 

NO. The cooling system would not function as designed if it was not open to atmosphere. Coolant expands as it is heated and has to have somewhere to go, which is the coolant reservoir, surge tank or whatever it is cooled. The radiator cap is a TWO-Way valve and has two "caskets." Look at it closely and you will see the two sealing surfaces. When coolant returns to ambient, it takes up less volume and coolant is returned to the cooling system through the radiator cap because of atmospheric pressure. Regards

 

It's 'called DG, not "cooled."

 

The gurgling you hear is air it will go away in time. Happens every time I do a cooling system service on my 03 and 09 camry.

 

Having replaced the radiator cap the purge/siphon function is now working. Now of course I'm a little concerned with what happened to the pieces of the old radiator cap.