2012 Prius - Engine Overheating

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If you turn on the engine, can you read the ECT temperature through your scanner?

 

Here's thermostat replacement instruction. Someone mentioned heating up old and new thermostats should be done in coolant? Seemed a little far-fetched to me, and the manual just says use water too.

Still, I think when thermostats fail, it causes excess cooling??

Addendum #1: attached Engine Temperature Coolant Sensor info.

Addendum #2: attached Engine Water Pump info.

 

It depends if the thermostats is stuck closed or open, usually the thermostats when it's bad is stuck closed, which causes the engine to overheat.

 

@Mendel Leisk do you mind attaching the file on how to test the ECT sensor. I'm not at home right now lol

 

Yeah I think you're right, I'm muddled: out-of-the-box the thermostat would be closed, it would be easy to fail thus. Funny, mine was the other way round though, it would open too soon, when I "raced" it with the new one. Also, brittle/fraying gasket made it half-open all the time.

Yeah think it's there now, misnamed as Engine Temperature Coolant sensor.

 

The fan works, I would check the ECT sensor. The ECT sensor turns on the fan when the engine coolant is hot in the engine, which prevents it from overheating.

There is 2 way to turn on the fan, one is manually through the AC control and the other is the ECU. The ECU receives all the signal from sensors and their devices from the engine, which will trigger the relays to turn on and off.

Like I've said, the relays and fans work, it might be the sensors not working properly by detecting the the engine coolant temp to turn the radiator fans on.

Have you checked the ECT sensor?

 

Nope, that's the only one.

 

For a long time I've wondered how common it could be for a thermostat to stick closed, considering what opens it is a blob of wax that will expand when heated ... seems like one of those "what happens when an immovable object meets an irresistible force" kind of situations. (I've noticed I actually have two home appliances where the engineers have used "wax motors" to open the door locks ... basically the same principle as the thermostat, a blob of wax with a heat coil around it, works the door lock when it expands. When the control circuit turns on that heat coil, it pretty much knows that lock will open, no matter how neglected, wet, and rusty it might get.)

But it seems like I found the answer on this web page by Stant: "A thermostat will fail 'closed' if the wax element has been damaged by overheating ..." Aha, that explains it. Let your engine get good and overheated (for some, non-thermostat, original reason), thermostat opens to full travel, wax still needs to expand, bursts its containment, result dead thermostat, and future overheating even after the real original cause gets fixed.

Therefore, they suggest replacing the thermostat any time an engine has severely overheated. Makes sense now.

-Chap

 

I was driving my Prius Alpha 2016, on hill side. when the speed is over 30 KM my car gives no problem, but when speed is below 20 KM after each 3 KM it display message that "Hybire system is overheated". I have to stop my car and turn off engine and wait for 30 mins them again after 3 KM on speed of 10 to 15 KM per hr same message appear.

my car is only 30000 KM driven and new. Give no problem if speed above 30 KM/H but when is rough and hill side it gie this message can some kindly guide me what is the problem . or i change my vehicle ?

 

If you're getting a warning there should be codes stored. Get dealership to check codes? Very new vehicle perhaps no charge for diagnostic, or under $100 (US) at most?

It could be clogging hybrid battery fan, though not sure. If you're handy this is something you could check yourself.

 

Need help with 2010 Prius, 2 months ago it threw P261b code. Changed water pump, cleared codes and the car ran fine for 2 months. Then it threw P261b, P261C. Bought SZ-TONDA. Had trouble getting the device to read ECU. Once we updated the computer and got access to ECU. I did a health check on all ECU's , the following Engine & ECT section reported that the calibration 34715200 and update "YES" and ABS/VSC/TRAC - calibration F152647106 - Yes. Cleared DTC, Engine Water Pump 0 RPM, Coolant Temp 180. I activated Water Pump manually and it stated speed was 3000 RPM in dialog box and speed requested was 3150 actual was 3950 RPM.

Has anyone seen these symptoms? Help would be appreciated

 

Please start your own thread. You aren't going to get much exposure on a thread started over 2 years ago.

 

Posting to an existing thread bumps it to the top of the list in "new posts", technically the same "exposure". That said, it probably is best to start afresh. But here we are, just keep going?

 

@Mendel Leisk
Thanks for attaching those pdf documents. I copied them to my Prius folder already. You never know when you would need them.

I had a thermostat failure on my 2002 E46 many years ago. It got stuck open. Coolant temps weren't getting over 160-165F. I got a CEL and replaced the thermostat. The thermostat on E46 using wax to open close but it also has a heater element for the ECU to open close it when necessary.