2014 Prius V overheating light on

how many miles on her? check for trouble codes with a prius aware scanner

 

You're playing Russian Roulette with your engine. I and many others would pull over safely and tow it to a shop or home.

Adding coolant yet?

Any head gasket leak stop added?

Odds are good it's a water pump which often fail gradually. It could be a head gasket leak adding gasses into the coolant while burning some coolant. This is generally preceded by rough rattling cold starts until it's really bad when it will shudder and rattle after a traffic light.

Head gasket sealant has been known to partially clog the micro channel radiator.

An outside and rare chance is a stuck open exhaust heat recirculation valve. Or an equally rare bad thermostat.

We will assume it is high miles which makes the water pump or head gasket likely.

Monitoring the engine temperature in early controlled conditions is diagnostic.

Finally, don't buy an aftermarket water pump. Your engine will suffer further and your car's reliability will continue to fall.

 

The red temperature lamp turns ON around 245F, just because it's not ON does NOT mean it isn't doing damage to your engine. Just that your below the 245F threshold. Normal operating temperature for that car is 185F-205F. All that plastic under your hood is suffering and will likely start warping, creating another set of future problems.

 

Yup, my 2015 did the same until I changed the HG.
You may just need a water pump and thermostat. BUT more likely whats happening is due to the HG leak into cylinders you now have air in your cooling system. IF there is enough coolant at the water pump it will flow but once it pushed that thru and coolant is too low at the pump car over heats.
Unfortunately that RED light comes on way too late. You have likely already at least blown HG, maybe even warped the head.
Keep using it and you can even bend the piston rods and engine is pretty much toast.