2012 Prius - Engine Overheating

take the pump out and hookup to 12v source,as for thermos3 place in boiling water to see it open

 

Your car might have a partially clogged radiator. What you're describing happened with my 92 Honda Civic that I had 10 years ago. I installed a new radiator - no more overheating.

I doubt it's the thermostat. It would need to be rusted pretty badly to be stuck closed and today's anti-freezes have enough rust preventative to assure the thermostat doesn't rust - unless the coolant is spent, unlikely with a 2012.

You probably would have heard the engine water pump making a lot of noise before it failed altogether.

Just the opinions of a DIY mechanic with over 30 years experience with trial and error repairs. A lot of errors in the pre-internet days but that's water under the bridge, whatever the hell that means.

 

The one thermostat I had go bad, failed in such a way that it was opening too soon, closing too late. Also it had fraying rubber gasket, so that even when "closed" it was leaking. In other words, it's failure caused over-cooling. This would become apparent after extended highway drives: lowish rpm, easy load, high wind speed through the front grill. Not sure if that's the usual, but that's my one case.

 

Welcome to your first posts on Prius Chat .

How many miles on your Prius? What part of CA are you in?

The thermostat is located at the water pump, so a drain on the coolant system helps.

I helped another member change out their water pump and thermostat several months ago. Good job to pool together.

Keep us posted.

 

1/2 mile is not going to get the coolant flowing. I'd just observe before pulling things apart just yet, unless you have a good reason to believe it is necessary at this point....

 

Probably use heated coolant, not boiling water, if you want to test the thermostat....

 

Sorry, should have clarified: my experience was on another vehicle.

 

What scanner are you using? Do you have Techstream? Can you see or hear what the engine water pump is spoiling up to (rpms)? How many miles on your Prius? What part of CA you from?

 

When AC is on, that's not the radiator fan that's turned on, it's your condenser fan. There are 2 separate fan in the front, ones for the engine and the other is for the AC, don't get those mixed up. Sounds like you're overheating due to the radiator fan not turning on. Is there any check engine light?

 

Looks like an expensive reader. Hope you had it laying around and didn't purchase for this issue.

I have Techstream on an old windows laptop and a $40 Kiwi2 reader paired with Dash Command on my iPhone. But it sounds like you can read some data.

Have you had any issues prior to this with your Prius? Noticed anything in the days prior to this incident? Original owner? Or owned for how many miles?

If it is not throwing any codes and there are no permanent codes logged in history, troubleshooting will be difficult . Codes will help narrow the issue down, but if nothing is there, it might have been a one off.

 

you're right, turning the AC on does activate both fans. I guess the hybrid system is different from conventional vehicles.

Your cooling fans should turn on though when your engine is hot, the ECU reads all of the engine coolant temperature, air
conditioning switch (on/off), air conditioning refrigerant pressure, engine speed, and vehicle speed signals to determine if it should turn on the fan relays which in turn start the cooling fan to cool down the engine... I would check the ECT sensors to see if its working properly.

 

With our accords there was a radiator and an AC fan, side by side, behind the radiator and condenser. IIRC the rad fan only came on for engine cooling, but when AC compressor was running both fans would run.

 

yeah I thought so too, but the Prius cooling fan turns both on together either through the ECU control or through manual AC control. I guess there is no condenser fan. I haven't checked the whole AC system on how it works, it might be a little different on hybrids.