2010 prius cooling system issues

Temperature light comes on. I started adding distilled water to the reservoir, but after a week or so that no longer works. The car overheated on the interstate a few minutes after I had just pulled over to add distilled water. More moderate hills taken at 45 mph will overheat it, too.

So yes, loss of coolant, although some of the loss happens when I open the cap to refill and I have to wait a minute while hot coolant gushes out. No severe rattling on engine starts. No mixture of oil and coolant. No noticeable white smoke from tailpipe, but maybe it's just a small leak into a cylinder? I'm going to pull the plugs tomorrow.

I've watched a handful of videos on head gasket replacement. I almost feel like I could do it successfully, but I'm not really sure.

Where in Techstream can I see those sensors?

Thank you for this.

I had already ordered a radiator and it came today (Fedex on a Sunday). I removed the pump and aimed a hose right into where the pump pumps into the block. I might try the driver's side of the engine tomorrow. Then replace the radiator.

Thanks so much for your in depth reply.

I did see that link in your signature. Thank you.

 

I normally use the Car Scanner phone app and a $35 Bluetooth obd2 interface for quick monitoring without a Techstream PC and hardwired obd2 interface. The pic above was from that phone app.

On Techstream you pick Engine and select Data List. Right click on "Coolant Temp" and move it to the top if desired.

You then pick Combination Meter and its Data List. The Combination Meter's
"Coolant Temperature" is the second coolant sensor and is downstream of the Exhaust Heat Recircation System on a hose near the egr.

Normally they will be with a few degrees of each when warmed up.

Its possible to select Dual Data List and see both on the same screen.

Generic Marked Up Dual List

Note the Engine ECU temp sensor is listed as "Coolant Temp" while the sensor downstream of the Exhaust Heat Recirc will be spelled "Coolant Temperature"

Techstream Basics part 2 attached

 

I ordered a Bluetooth obd2 interface last night. I got one a while back that didn't work. This time I ordered [the primary] one that the Dr. Prius app developer recommends.

I never knew about the Dual Data List. Thanks for that and the Techstream Basics pdf.

With the garden hose I flushed the big pipe under the edge of the inverter and it came out the water pump housing (pump still removed). In combination with what you said earlier I feel better. ("Most of the small coolant hose devices are not going to overheat the engine even if they are completely blocked...It's the big radiator hoses, the radiator, thermostat and engine water pump that are important.")

While I have things apart I'm going to clean the EGR today, inspect the plugs (and maybe replace), and replace the radiator. Once I have the cooling system back together I'll put distilled water in, get it up to temperature, drain it a few times, do a longer test drive and see what the status is. Thanks again for your help!

 

Same here, thanks @rjparker!

is there a part one, or is it just some sort of intro?

 

Hope for the best. Verifying the two coolant temp sensors is easy with the right setup but if they or the radiator are not the problem there is still the most common reason for sealer - eg head gasket leaks burning coolant.

If ithe hg needs verification a dual view borescope with the engine cold and thr coolant system under manual pressure is best.

Car Care Nut HG Borescope at 660s

 

Yes part 1 is mostly intro. Some old school functionality that required online access like ecu programming is deactivated now that Toyota has moved to GTS+. Meanwhile some free apps do the basics better and some third party scanners do much of the more elaborate features without subscriptions.