2008 Inverter Fluid

It might be a bit too soon to change the inverter fluid just yet. Has the inverter pump recall been performed? If so, then the fluid should have been changed already, although some dealers do not do this.

 

It's OK to change the transaxle ATF at this time.

The first specified change on the inverter/transaxle coolant is at 100K miles and there really is no need to do this sooner. Subsequent changes are at 50K miles.

When you are ready to do this, buy a gallon of Toyota Super Long Life Coolant and an aluminum transaxle drain plug washer from your local Toyota dealer's parts dept.

Before you start, make the Prius READY and listen to the inverter coolant pump, located behind the driver's side headlight, after the engine turns off. Notice how the pump sounds like an aquarium pump and you should not hear any air bubbling. Look at the inverter coolant reservoir and note the turbulence in the fluid as well as a step in the fluid level as you look across the front to the back of the reservoir. You need to replicate these sounds and sights after the fluid drain/replace, before you can say you are done.

The coolant drain plug is located on the bottom of the transaxle, nearest to the engine. Do not confuse with the transaxle ATF drain plug which is further away towards the driver's side of the car. Both drain plugs require 29 ft.-lb tightening torque.

Remove the coolant drain plug and measure the coolant drained, typically 1.5 quarts or so. Now you know how much new fluid you need to add before you can declare victory on this project.

Remove the large black plastic cover over the radiator for access to the inverter/transaxle coolant bleed valve. There are six plastic fasteners for the cover. Use a Philips screwdriver to rotate each fastener as you apply upwards pressure on the cover, to pop the fastener out. If you break a fastener (the plastic is brittle especially in cold ambient temps), get a replacement at your Toyota dealer.

Fill the inverter coolant reservoir. Make the Prius READY. The inverter coolant pump will be noisy and you'll also hear air bubbling in the system.

Run a clear vinyl hose from the bleed valve to the coolant reservoir opening. Open the bleed valve and let air bubble out through the hose into the reservoir opening. Keep the fluid level at the MAX level in the reservoir.

After a while, you'll notice that the inverter coolant pump has quieted down and you will not hear air bubbling. You should have added the same amount of new fluid as you had earlier drained out. Tighten the bleed valve and the inverter coolant reservoir cap, replace the black cover over the radiator, and you are done.

Once you start this project you cannot rest until you have gotten all air out of the system and restored correct fluid circulation. The continued health of the inverter and transaxle depends upon this cooling system. Hence, allow yourself a couple of hours to account for learning curve and to ensure you have plenty of time to do the job correctly.

 

Good information...

Prius 30k Service

 

I see in my manual under specifications that the Power Control Unit (Inverter) coolant capacity is 2.9 quarts. I haven't done this job myself yet, so I can't quote from experience. Is this typical Toyota "absolute" capacity, or does some of the old coolant remain in the system when it is drained?

 

Some old coolant remains in the system. Same is true with the engine coolant, where the NA Prius capacity is around 9 quarts but you will be lucky to get 6.5 quarts out of the system after opening all three drains: radiator, engine block, and CHRS canister.

This is why the service interval is 100K miles for the factory fill coolant; then 50K miles for subsequent changes.

 

I changed mine at 30,000 after noticing it was getting a little cloudy. Buy a gallon of SLLC at Toyota for $20.
Pour a little in a clear glass. Then using a turkey baster suck out a little out of the Inverter reservoir and put in a clear glass.
Compare the 2. You'll probably see how cloudy the original is. The I coolant is exposed to a very large amount of pure aluminum heatsink which is very corrosive.

Its pretty easy to change and I usually that coolant and the trans fluid every 30,000. For me that's every 3 years. Both are very inexpensive when you diy it.
$40 for trans fluid & $20 for SLLC.

Btw, I noticed an immediate gain in mpg's after changing the I Coolant. The Inverter ran cooler as I checked it with a IR thermometer before and after. Go for it.

 

I agree with nh7o--try to find out if the inverter coolant pump recall was performed. If so, the inverter coolant may have recently been changed. Mine was done last fall.

 

They typically do not replace the fluid with a pump install. They just duckbill off the hoses and slide it in.

 

My newly purchased 2008 prius just had the pump recall performed at no cost to me.
I encourage you to go to Toyota Owners (Toyota Owners Official Web Site: Service Coupons, Owner's Manuals, Service Scheduling And More) and register the serial number of your Prius. There's quite a bit of info available to you about your car. It even shows if the pump recall needs to be performed.