Replacing Coolant Temperature Sensor

For access you may want to remove wipers and cowl. Watch @NutzAboutBolts spark plug change video, linked here:

Nutz About Bolts Prius Maintenance Videos | PriusChat

The thermostat is at the highest point in the system, so coolant spill should be minimal, and it’s also the air-bleed location.

Coolant is Toyota Super Long Life, available in gallons (or 4 litre, in metric countries).

“number one engine cover” MAY be that ornamental plastic piece atop the engine valve cover; I’m forgetting “Toyota speak”.

how many miles on it?

 

Out of the two coolant temperature sensors the engine has, are you sure that's the one you think needs replacement?

I'd recommend looking over this post (and following in that thread) to clarify where both sensors are.

If you have Techstream, you see the reading from the one in the cylinder head in the Engine and ECT data list, and you see the reading from the one in the hose tee in the Combination Meter data list.

As you can see in the linked thread, you can also see both readings in at least some smartphone apps, but I can't tell you for sure which one is $7C0 and which is $7C4. You could unplug one or the other and see which reading goes super-cold, and then you'd know.

Thethermostat (only one of those) is located very low on the engine, behind the water pump.

 

Has anyone actually confirmed which sensor is which ($7C0 vs $7C4)?

 

If you use Techstream, one of the readings will be shown in the data list for "engine and ECT" (that's the one in the cylinder head), and the other will be shown in the data list for "combination meter" (that's the one in the exhaust heat recovery loop).

I don't know them by their 7C0/7C4 addresses.

 

I just did mine 2 days ago. This is the one in the side of the block. It cost $19 on Amazon. Beck/Arnley 158-0783 Engine Coolant Temperature Sensor https://a.co/d/ej7NsGI

The official Toyota way takes hours and lots of removals. I basically unbolted the coolant bottle, the bracket that holds it (along with the HV wires) - this gives a straight path into the sensor. There's 2 YouTubes that show this. It's hard to reach and see. I used super long needle nose to unsnap the 2 wire connector from the sensor - it's a PITA operating with little room, but it works. It's a 19mm deep socket *but* that would not work for me. I needed the next up size in standard non metric cause it needed to go over the electric connector, n the 19 just didn't make it over it. I had to use a stubby drive cause there's little room, and two small extensions to get the length right.

This is the second one I've done on a 2010 Prius, n it really took about 40 minutes each time. It just takes patience. I did not drain the coolant - maybe 8 ounces leaked out, but it's environmental coolant .

Again, YouTube it - it's not crazy ... Really a 30 minute job

 

FYI - to find the right size socket, buy the sensor, and use it as a guide - I think I used a 3/4 inch deep socket - when you look at it, it's clear it works n won't strip the sensor.

FYI2 - when I removed the old one, the electrical blob on the end twisted off (broke) first - then the socket sat over the copper body n it came out easy...