Coolant Replacement Interval

Drain & fill of the cooling system (ICE or Inverter) doesn't get rid of 100% of the existing coolant. The NEW coolant you are adding gets mixed in with the OLD coolant in the loop (ICE or Inverter); essentially the 10year/100K mile service life of NEW coolant is getting diluted.

On the Gen2 Prius, I believe the ICE loop capacity is 9 quarts. When I last drain/fill, only about 1.5 gallons came out (6 quarts), so 3 quarts remained.

ArtsAutomotive has a view of 2-3year/30K Mile coolant change interval. LINK Granted he is a service shop and makes money by doing procedures. He has a good reputation and the points he makes are valid. If you learn to DIY, its cheap and you'll do it faster each time.

The inverter coolant looks pretty good at 30K miles. The ratio and pH both test OK as well. So why are we changing it? Because:
1) Toyota SLLC is just regular ethylene glycol silicate-free premixed coolant with pink dye, and ethylene glycol coolant has had a 2-3 year service interval for as long as I can remember.
2) The components it protects (the HV transaxle & inverter) will set you back about $7000, just for the parts!
3) The idea is to replace the coolant before it goes bad to provide continuous protection.​

 

For Gen III, two gallons is enough for a full change.

The ECU circuit capacity is about 1/2 gallon or two quarts.

I agree with Art's Automotive.

Also, changing coolant in a Gen III is much simpler than in a Gen II.

There is no special procedure.

There is a drain plug that requires a 10mm socket hex wrench at the bottom on the transaxle.

You drain the ICE circuit by draining the radiator at the petcock.

 

Any car I've had over the years had a long first interval, then shorter subsequent intervals. Just my guess: corrosion or crud accumulation accelerates as the vehicle ages?

 

Would anyone know were there might be a writeup on how to change the coolant on a gen 3? Everything I can find is for a Gen 2 with the termos tank behind the bumper. How do you get the ICE to idle to bead out the air?

 

Ready-off, accessory mode on.

Apply parking brake.

Double push the accelerator pedal to the floor in park.

Put the car in neutral (still ready off)

Double push the accelerator pedal to the floor.

Put the car back in park.

Double push the accelerator pedal to the floor.

Warning appears.

Ready-on the car.

This is maintenance mode. Engine will run continuously until you ready-off. Do not drive the car in this mode.

 

Thanks!!! Any Clues on how to find the engine block drain plug?

 

I believe back of the engine underneath the exhaust manifold closer to the front/timing cover of the engine. Forgive me because I can't remember, the Toyota diagram isn't the greatest, and I don't have one in the shop right now to take a picture for you.

 

It would help, if you identify the type of head on the drain plug and the wrench size needed to remove it.

 

Usually a brass 10mm

 

Will look for it. Thanks.

 

At 68,800 miles and over five years old, I am planning to change the coolant in both the engine and inverter in the next few weeks. It has been mentioned that there is an air release valve on the 2010 model engine and questions asked about where it is and what it looks like. The air release valve is opened to bleed air out of the system while refilling with new coolant. For those that have one, it is under the cowl on the right side of the engine (as viewed from the front of the car). It has a white turning knob on top and a pipe stem to attach a hose. Mine also has a blue dot on the front, as pictured below.



It would be appreciated if someone can post a picture of the engine drain cock. I have not as yet found it.

 

What coolant should be used in the change? The Toyota stuff or some quality aftermarket silicon free fluid?

I'll check the repair literature I have for the Toyota procedure & post that if I can.

 

On MY2011 and later vehicles, the step involving removal of the block drain plug has been eliminated from the service instructions. The design and part number of the plug itself changed as well. I recently performed the drain and refill using the Uview Air Lift and drained the ICE cooling circuit only using the radiator drain cock.

Jeff

 

Yesterday I drained and refilled the engine and inverter coolant on my 2010 Prius hatchback and located the engine drain cock. The engine drain cock is difficult to see. It is located on the back, passenger side, of the engine directly above the end of the oil filter canister and above an "L" shaped bracket, higher up on the engine than you might think it would be. From underneath, the small drain pipe blends with the engine color and partially blocks the view of the brass colored bolt above the pipe so it easier to locate by side view, looking to the right from the left side of the engine. There are a lot of parts in the way so you have to look up and around them until you see it. A bright light helps to cause a reflection from the brass colored bolt head. Once you find it, it is obvious where it is and easily relocated. It was difficult to get good pictures of the engine drain cock. Below is a close-up picture and another picture shot from below.






Observations and Comments:

• If your car has an engine drain cock, it is worth finding and opening to get a complete engine coolant drain. The drain pipe accepts a 5/16" ID hose which you can then run to a catch pan and drain the engine with no mess. The radiator drains via a petcock. You can drain both the engine and radiator simultaneously.
• I did not use the engine air release valve because I used my AirLift II tool which worked very well to refill and keep air out of both systems. If you don't have an AirLift tool, the engine air release valve will help a lot with expelling air from the engine system while refilling. If you don't have an AirLift tool or an air release valve on your engine, you can still circulate the air out by filling the overflow tank only half full and running the engine in "Maintenance Mode" until the air comes out by circulation through the overflow tank; it just takes longer.
• Putting the engine in "Maintenance Mode" is easy after you realize that you have to step on the brake in order to shift from Park to Neutral and then again to go from Neutral back to Park.
• I had to remove the engine coolant overflow tank to remove all the old coolant from it.
• A small amount of sediment came out of the engine which is normal for five years and 68,800 miles. The used engine coolant was slightly darker than new coolant which is also normal. The used Inverter coolant was about the same color as new coolant.
• The Inverter drain and refill posed no special problems.
• It took about 7.5 quarts of Toyota SLLC to refill both the engine and inverter.
• Two gallons of Toyota SLLC and a new Inverter drain plug washer cost $54.14 from my Toyota dealer.

 

I drained and refilled both cooling systems today. Based on another website, I flushed both systems with distiller water. I did this twice on the inverter system to get out almost all of the "pink" old fluid. I did it once on the engine cooling system.

The air bleed valve was difficult to open on the engine system. It required pliers, and because it's beneath the windshield wiper tray, access is a challenge. I took off the plastic engine cover to make access a bit easier. The engine block drain was also hard to find, but it helps that it's brass.

The inverter coolant change is super easy. My local Toyota dealer had a hell of a time finding the gasket. They'd never heard of anyone doing this service before, including the dealership mechanics.

 

The sealing washer is 18mm ID aluminum. It is the same washer used for the transaxle drain and fill plugs. The drain plug is the same as the ones for the transaxle.

 

I just climbed out from under the car, my engine block drain does not look anything like that, there is not a tube, just a Black headed bolt and the bracket that goes over it with the sensor attached like in the 1st photo above. Do all 2010 models have the drain? Can i still do it without draining the block? I tried to take a picture but my camera died and I got PB blaster in my eye.

 

Try looking and feeling above the "black headed bolt and bracket". That is where the engine drain valve is located. You should have an engine drain valve on your 2010.