The coolant for the inverter/converter and hybrid transaxle system is a routine maintenance item for hybrid owners. CARspec had the opportunity to replace the coolant for the owner of a 2006 Highlander hybrid today and wanted to share some of the quirks of the system, mainly the bleeding of air from the system after refilling.
The drain for the hybrid coolant is located on the bottom of the hybrid transaxle – it is a 10mm allen. There is an additional drain on the front radiator assembly as well – the hybrid system on this 3.3 liter V6 hybrid drive system has a separate radiator for the engine and hybrid drive components. Here it is circled at the bottom of the photo, the upper radiator grill removed:
Once all the coolant is out from both drains close them and open the air bleed on the radiator, as seen above. When filling the hybrid cooling system this is crucial to help get as much air out of the system before you run the vehicle. You can then fill the reservoir:
Shown above are both the engine and hybrid cooling systems being bled of air. CARspec uses Toyota’s Techstream diagnostic software to run the hybrid system’s water pump for a time until there is no audible gurgling sound. This indicates (combined with strong coolant flow in the reservoir next to the inverter/converter) that all of the air is bled out of the cooling system. On this vehicle the engine’s cooling system was bled of air only after the hybrid cooling system was confirmed air-free to minimize the change of an overheating hybrid system.
As Eden Prairie and Chanhassen’s independent Toyota and Lexus repair specialist we’re happy to offer this routine maintenance item most auto mechanics aren’t familiar with. Using Toyota genuine coolant and factory repair procedures, tools and software, CARspec can take care of any of your hybrid needs. Call us at (952)426-4798 to make an appointment today!