I looked around for informaiton on how to replace the inverter coolant and found plenty for the Prius, but our HiHy's are built slightly differently. I decided to post a quick How-To for others needing to do this. Its a simple job that takes about an hour or less if you have everything you need assembled.
The reason I needed to do this is because I noticed a little pink puddle in front of our HiHy one day. On investigation, I noted a pink crusty-ness of dried antifreeze around the lower mounting point of the inverter radiator. On further investigation I found that one of the 4 bolts holding the inverter radiator to the car was missing, allowing the inv-radiator to 'wobble' slightly as the car is driven, causing the weld point on the lower driver side mount to work into a small crack. Right where the pink crusty was located.
Therefore, this guide goes into greater detail than you need if you're just replacing the fluid. You should be able to pick out the appropriate parts for the fluid change and ignore the rest.
The first pic is an excerpt I found on the web of a presentation related to working on several models of hybrid vehicles and the potential danger. It goes through several steps with a couple of pics that are very helpful. This is the basic guide. I'm adding just a couple of tips and some pics to make it clearer in the event you have to replace the radiator.
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Tools and Supplies -
You'll need assorted tools you would normally find in an average garage: Metric socket set, some metric box wrenches, phillips screwdriver, flat screwdriver (to help pry off the 2 hoses), and pliers with jaws wide enough to compress the 2 hose clamps.
10mm Hex head/allen
1 gallon of Toyota Super Long-Life Coolant (SLLC)
New drain plug gasket/washer.
Note about the drain plug - I had the Toyota parts rep look up the drain plug on his schematic - he couldn't find it. He's never heard of it or of changing the inverter coolant, citing that it is pretty much permanent. I pointed out where I thought it would be and we found it, part number 90430-A0003, Gasket. The plug isn't labled as you would expect. It is labeled as something like 'water plate bolt'. There is a plate on the bottom of the transaxle that is sealed and bolted on. In that plate is a 10mm hex plug that is the drain. Unlike the Prius, there is no other 'plug' in the vicinity, so you are less likely to mix them up. The washer is a soft aluminum crush washer meant to conform to the surfaces. You might be able to use the old one over, but for about $2 a new one is good insurance. I've included a picture of this plug as this was the most unclear part of the job for me when I started.
Tips -
- Remove the front grill to make things easier to get at. There are 6 pop-its along the top of the grill. Pull them out. Then, gently work the grill forward applying pressure from behind - you can work your hand in there. There are 4(?) tabs on the bottom of the grill that fit in to slots on the front bumper cover, with the tabs having small 'bumps' to somewhat lock the tab in once you've pressed it in far enough. They will pop out with enough pressure. Set the grill and 6 pop-its aside.
- Remove the hood latch mechanism by removing the 2 10mm bolts that are visible along the sides. Remove the black plastic cover on the bottom of the latch mechanism to get at the 3rd 10mm bolt. Once the latch is loose, you'll note an arm that extends further to the pass side and the cable that extends to the driver side. Drop the pass side down enough to unclip the wire connector, then lay the latch over into the engine compartment to get it out of the way.
- Remove the vertical reinforcement bar behind the hood latch by taking out the 2 10mm bolts - one on top and one on bottom - and the 1 Phillips screw connecting to the front bumper cover. The front temp sensor is attached to this bar. Once loose, lay it over into the engine compartment too.
- Remove the 2 bolts holding the 2 horn elements to the car and lay them over into the engine compartment. Going from memory, these are either 12 or 13mm.
Now the inverter radiator is exposed pretty nicely.
Place a small hose over the lower radiator drain stopcock as indicated in the instructions. I had a 3/8 clear tubing around that worked fine. Place the other end of your hose in the drain pan you've selected. Open the drain stopcock and the top of the inverter coolant reservoir. Fluid should start draining. Once it has drained a bit, open the second stopcock on the top of the radiator to aid in draining. This is an air-bleed stopcock you'll use later. Note you don't need to remove the two covers over the coolant reservoir unless you want to. I did, but could have gotten by without.
Once it has drained out, close up the bottom stopcock, move your pan, and shimmy under the car to get at the 10mm drain plug. Remove the plug with the 10mm hex. The SLLC will drain quickly. Replace the washer, replace the plug after it has finished. I don't know the proper torque, but I snugged it pretty good - don't want this droping out on the highway. If someone who has access to a service manual could reply with a torque spec that would be great for anyone doing this in the future. Note this plug did not have any sealant.
![Image]()
To remove the inverter radiator, with pliers, compress the hose clamp on the driver's side and slide it down on the hose. Using the flat screwdriver, work the hose off the tube. You'll need to slide the pan under the area to catch the SLLC that pours out which wasn't drained.
Remove the 4 10mm bolts holding the 4 corners of the radiator onto the main radiator behind. Note the pass side hose is still attached and the radiator moves round.
To get the pass hose off, slide the radiator to the driver's side. This gives you some working room to get at the hose, which pretty much turns into the engine compartment if you don't pull it to the side. Again, pliers to compress the hose clamp, slide down the hose, work the hose off the radiator tube.
To install your new radiator, follow the steps in reverse, starting with getting that pass hose on first.
Once you're all bolted up and clamped, check to make sure the radiator bottom stopcock is closed, then pour SLLC into the top reservoir until it hits the full mark and stops going in. You'll hear gurguling noises as it drains down into the transaxle and radiator. Keep an eye on the top stopcock as once the air in the radiator evacuates you'll start to drip SLLC. As SLLC comes out the top radiator stopcock, close it and continue to fill the top reservoir until it is full.
Instructions state that if you turn the key to the ON position, that the inverter radiator pump will cycle the fluid to get the air out. That didn't work for me. I needed to actually run the engine for the pump to come on.
The instructions show how to route the tube from the top radiator air bleed stopcock back into the top reservoir. I had a small funnel in the top reservoir and the tube zip tied to the edge of the funnel to hold it in place. I started the car and noted immediately the air and SLLC with bubbles ran out the tube into the top.
Keep topping up until it looks like all the air is out. Once you have it, close the air bleed stopcock, remove the tube, top off and close the top radiator.
Reassemble everything in reverse if you've disassembled to remove the radiator. If you're just changing the SLLC, I'd still recommend removing the grille as it would be tough to get into the area of the stopcocks otherwise.
Good luck. Hope it helps.
![Image]()
The reason I needed to do this is because I noticed a little pink puddle in front of our HiHy one day. On investigation, I noted a pink crusty-ness of dried antifreeze around the lower mounting point of the inverter radiator. On further investigation I found that one of the 4 bolts holding the inverter radiator to the car was missing, allowing the inv-radiator to 'wobble' slightly as the car is driven, causing the weld point on the lower driver side mount to work into a small crack. Right where the pink crusty was located.
Therefore, this guide goes into greater detail than you need if you're just replacing the fluid. You should be able to pick out the appropriate parts for the fluid change and ignore the rest.
The first pic is an excerpt I found on the web of a presentation related to working on several models of hybrid vehicles and the potential danger. It goes through several steps with a couple of pics that are very helpful. This is the basic guide. I'm adding just a couple of tips and some pics to make it clearer in the event you have to replace the radiator.
Tools and Supplies -
You'll need assorted tools you would normally find in an average garage: Metric socket set, some metric box wrenches, phillips screwdriver, flat screwdriver (to help pry off the 2 hoses), and pliers with jaws wide enough to compress the 2 hose clamps.
10mm Hex head/allen
1 gallon of Toyota Super Long-Life Coolant (SLLC)
New drain plug gasket/washer.
Note about the drain plug - I had the Toyota parts rep look up the drain plug on his schematic - he couldn't find it. He's never heard of it or of changing the inverter coolant, citing that it is pretty much permanent. I pointed out where I thought it would be and we found it, part number 90430-A0003, Gasket. The plug isn't labled as you would expect. It is labeled as something like 'water plate bolt'. There is a plate on the bottom of the transaxle that is sealed and bolted on. In that plate is a 10mm hex plug that is the drain. Unlike the Prius, there is no other 'plug' in the vicinity, so you are less likely to mix them up. The washer is a soft aluminum crush washer meant to conform to the surfaces. You might be able to use the old one over, but for about $2 a new one is good insurance. I've included a picture of this plug as this was the most unclear part of the job for me when I started.
Tips -
- Remove the front grill to make things easier to get at. There are 6 pop-its along the top of the grill. Pull them out. Then, gently work the grill forward applying pressure from behind - you can work your hand in there. There are 4(?) tabs on the bottom of the grill that fit in to slots on the front bumper cover, with the tabs having small 'bumps' to somewhat lock the tab in once you've pressed it in far enough. They will pop out with enough pressure. Set the grill and 6 pop-its aside.
- Remove the hood latch mechanism by removing the 2 10mm bolts that are visible along the sides. Remove the black plastic cover on the bottom of the latch mechanism to get at the 3rd 10mm bolt. Once the latch is loose, you'll note an arm that extends further to the pass side and the cable that extends to the driver side. Drop the pass side down enough to unclip the wire connector, then lay the latch over into the engine compartment to get it out of the way.
- Remove the vertical reinforcement bar behind the hood latch by taking out the 2 10mm bolts - one on top and one on bottom - and the 1 Phillips screw connecting to the front bumper cover. The front temp sensor is attached to this bar. Once loose, lay it over into the engine compartment too.
- Remove the 2 bolts holding the 2 horn elements to the car and lay them over into the engine compartment. Going from memory, these are either 12 or 13mm.
Now the inverter radiator is exposed pretty nicely.
Place a small hose over the lower radiator drain stopcock as indicated in the instructions. I had a 3/8 clear tubing around that worked fine. Place the other end of your hose in the drain pan you've selected. Open the drain stopcock and the top of the inverter coolant reservoir. Fluid should start draining. Once it has drained a bit, open the second stopcock on the top of the radiator to aid in draining. This is an air-bleed stopcock you'll use later. Note you don't need to remove the two covers over the coolant reservoir unless you want to. I did, but could have gotten by without.
Once it has drained out, close up the bottom stopcock, move your pan, and shimmy under the car to get at the 10mm drain plug. Remove the plug with the 10mm hex. The SLLC will drain quickly. Replace the washer, replace the plug after it has finished. I don't know the proper torque, but I snugged it pretty good - don't want this droping out on the highway. If someone who has access to a service manual could reply with a torque spec that would be great for anyone doing this in the future. Note this plug did not have any sealant.
To remove the inverter radiator, with pliers, compress the hose clamp on the driver's side and slide it down on the hose. Using the flat screwdriver, work the hose off the tube. You'll need to slide the pan under the area to catch the SLLC that pours out which wasn't drained.
Remove the 4 10mm bolts holding the 4 corners of the radiator onto the main radiator behind. Note the pass side hose is still attached and the radiator moves round.
To get the pass hose off, slide the radiator to the driver's side. This gives you some working room to get at the hose, which pretty much turns into the engine compartment if you don't pull it to the side. Again, pliers to compress the hose clamp, slide down the hose, work the hose off the radiator tube.
To install your new radiator, follow the steps in reverse, starting with getting that pass hose on first.
Once you're all bolted up and clamped, check to make sure the radiator bottom stopcock is closed, then pour SLLC into the top reservoir until it hits the full mark and stops going in. You'll hear gurguling noises as it drains down into the transaxle and radiator. Keep an eye on the top stopcock as once the air in the radiator evacuates you'll start to drip SLLC. As SLLC comes out the top radiator stopcock, close it and continue to fill the top reservoir until it is full.
Instructions state that if you turn the key to the ON position, that the inverter radiator pump will cycle the fluid to get the air out. That didn't work for me. I needed to actually run the engine for the pump to come on.
The instructions show how to route the tube from the top radiator air bleed stopcock back into the top reservoir. I had a small funnel in the top reservoir and the tube zip tied to the edge of the funnel to hold it in place. I started the car and noted immediately the air and SLLC with bubbles ran out the tube into the top.
Keep topping up until it looks like all the air is out. Once you have it, close the air bleed stopcock, remove the tube, top off and close the top radiator.
Reassemble everything in reverse if you've disassembled to remove the radiator. If you're just changing the SLLC, I'd still recommend removing the grille as it would be tough to get into the area of the stopcocks otherwise.
Good luck. Hope it helps.
