Coolant Change for Eng & Inverter???

[joeman]

About to take on changing coolant for Engine and the Inverter in my 2002 71k Prius. Would be interested in tips or links on how to change both. I have a cheap manual that gives me some information. The inverter looks like the tricky one, there are two bleeders involved. I plan to upgrade both to the Gen 2 coolant.

Thanks for any help.

Joe

[Patrick Wong]

Hi Joe,

The engine coolant drain and refill process is pretty standard. The major issue is to find the radiator and engine block drain cocks. The radiator drain cock is on the bottom of the radiator, I recall it is on the driver's side.

The engine block drain cock can be found on the side of the engine facing the firewall. To find that, raise up the car and get under it so that your feet are sticking out by the front bumper and the engine is over your chest. Then look up and you should be able to see the block drain cock.

After you've filled the coolant, you'll need to get the Prius into Inspection Mode so that the engine runs continuously. If your manual does not explain how to get to this mode let me know. While the engine is running, keep the radiator topped off as the fluid level drops and turn on the cabin heater to MAX HEAT so that coolant will flow through the heater core and air will purge out. Squeeze the top radiator hose to further encourage air to get out of the system.

After you think you've gotten as much air out of the system as you can, replace the radiator cap and drive the car around for a test drive. After you turn off the car and the engine cools down, check the radiator and overflow tank again, refill as needed. Continue to check the radiator and overflow tank daily until the levels no longer drop.

You are right that the inverter coolant drain process is more complicated due to the need to purge air out of the system. Before you start, listen to the sound that the coolant pump makes when the car is IG-ON (not READY.) The pump is near the driver's side headlamp. Look at the inverter coolant reservoir and note that the fluid level is higher at the front, compared to the rest of the reservoir.

Drain the inverter coolant by removing the drain plug on the transaxle using a 24 mm socket (or 15/16"). There are two drain plugs on the underside of the transaxle. You want the one closest to the engine. If you remove the other drain plug, you'll drain out the transaxle ATF, so pls don't make a mistake.

After you've drained out the inverter coolant, replace the drain plug and tighten to 29 ft.-lb. Ideally you will replace the aluminum washer, you can buy a replacement from your Toyota dealer parts dept for ~$2 or so.

Fill the inverter coolant reservoir with Toyota SLLC. Make the car IG-ON and continue to fill the reservoir as the level drops. Once the level is stable, turn off the car. Attach two clear vinyl hoses to the two valves and insert the other end of each hose to the reservoir opening. Make the car IG-ON again and open the valves to purge air out. Once you no longer see air coming through the vinyl hoses, close the valves. Continue to work on this until you don't hear air flowing through the inverter coolant pump and you see the fluid level at the front of the reservoir is higher than the rest of the reservoir.

For more info check out techinfo.toyota.com and download the relevant repair manual pages. $15 for a two-day subscription.

You also might want to measure the amount of drained coolant that comes out, so that you will know how much new coolant you have to add before you can declare victory.

[joeman]

Patrick,
When you mention eg-on referring to toping off the inverter coolant, do you mean key switch is in on position. Or do you mean I should turn the key so it turns over the engine?
Thanks for the excellent instructions and taking the time to post it. Hopefully this will help others that need some advice on coolant changes.

Joe

[Patrick Wong]

Hi Joe,

Yes, IG-ON means that the key is at the on position where all of the instrument panel warning lights are on and the car is not READY. ACC-ON is where the warning lights are off and you can turn on the radio.