Temperature light on and off after water pump change?

Are you sure it's the temperature light? It's more likely the oil pressure is low, you should check your oil level.

You changed your water pump at 60k miles or you've traveled 60k miles since replacement? It's possible for failures to occur, regardless of mileage. So it could fail again.

But these cars are known for headgasket failures and missing coolant. I would check you have a full reservoir of coolant and it's not going into your engine.

If you changed the pump at 60k miles, I would be curious if Toyota even did the replacement. Could've just given you back your car and say "All done"

 

Was it an OEM pump? Did the place PROPERLY bleed the system?
Are they familiar with the Prius cooling sytem?

 

I would monitor the temp with a Bluetooth app and interface ($35) to understand what my temperature is doing. If it’s running higher than 200f most of the time and over 210f at anytime you have a problem in the cooling system. Without a water pump code and check engine your engine went up to 248f assuming you saw the temperature light.

Besides the water pump you might have a radiator fan failure. Inspect with AC on which will energize both. There is a small chance that high fan mode could fail one fan due to different relay modes.

Radiator clogging could reduce cooling ability, usually caused by sealers.

 

Could it be a temperature sensor? How are the electrical connections to the radiator fans (and electric cooling pump) doing? Getting online with a bidirectional OBD2 scan tool might help you with checking these. I also wouldn't use anything but the Toyota coolant in my Prius.

I also think what others have said are things to look into. (Quality parts, bleeding, history of sealers...)

 

With a scanner you check the temps after the car has cooled overnight. They should be very close to ambient. A really broken sensor will code for opens or shorts. Overall sensors are reliable. In the Prius you have two and can compare with the car warmed up.

These are the two engine coolant temps. The first is direct to the combination meter. When fully warmed up they will be within a few degrees of each other.

 

If it's that bad, you may need more than just the head gasket.
The head is likely warped badly. And may not be able to machined safely.

 

It would seem you had an overheating issue since Feb 2023. How was it resolved then? Sealer?

I agree with dogman, it is likely the engine needs to be replaced if oil is flowing into the cooling system.

 

oil

 

Not likely but it would be in the inverter coolant, not the engine coolant.

If it’s a nice 2011 trim 5 I would get a Hybridpit engine and enjoy no oil consumption, no oil leaks and no head gasket problem.

 

@preeeuss it’d really help if you could clarify the mileage on the car now, and the mileage at which the pump was changed.

Also, were the water pump and thermostat replaced at dealership?

 

Feb 2023 when car was overheating he changed waterpump

Oct 2024 when oil pressure sensor dumped oil

Nov 2024 oil in coolant. Bad news.

 

^ Ah, the ol’ why continue an existing thread, on the same subject, with vital statistics finally sorted out, when you can start a new thread and start the process all over, trick.

Time to hit unwatch.

And ignore.

 

I do not think it was a thermostat problem. I think there is more to this story. You have a major problem with the engine. Come back again and continue this thread when it overheats again.

 

Just HOW did you determine it was the thermostat?