2021 Lexus RX450hL Hybrid Inverter Coolant Drain, Flush & Refill Cost

Hybrid drive vehicles which use electricity must store that electricity in a direct current (DC) battery. Since the hybrid drive motor uses alternating current (AC), the hybrid inverter must be used to change DC power to AC power. As you may imagine, the high voltage used in the hybrid battery creates a large amount of heat in the inverter as current is changed from DC to AC, so a cooling system must be used. This is much like the cooling system on an engine.

High voltage creates high heat, so the metallic case of the inverter generates lots of heat which must be transferred to a liquid via indirect contact. The cooling system for an inverter may run over, under, around, through, or to the side of the inverter, and the purpose is to absorb the heat byproduct of electricity changing from DC to AC. The coolant passages touch the inverter, the heat moves from the inverter to the cooling passages, and the cool liquid inside the cooling passages absorb that heat and carry it to the radiator. Wind blowing across the radiator cools the liquid in the reverse manner, and the hybrid inverter cooling system pump pushes the cooled liquid back through the cooling passages again.

The inverter will become hot if the hybrid inverter cooling system decreases in efficiency. This may happen if the coolant becomes too old, turns corrosive, or becomes contaminated. When this occurs, the hybrid drive system warning lamp will appear, and the hybrid drive control module will reference the inverter becoming too hot. Also, the hybrid drive system may possibly cease function, and the operation of the vehicle may be suspended as well. However, more often than failure occurs, the system requires a flush, drain, and refill because or system repair or scheduled maintenance.

Hybrid component failure requires immediate repair. In many cases the vehicle will need to be towed to a repair facility, and servicing the vehicle is not possible without manufacturer specific or hybrid drive training. For vehicles that need the inverter cooling system flushed, drained, and refilled due to scheduled maintenance, this should be done on time or slightly early. It is not wise to have services performed after the service interval has elapsed.

All hybrid vehicles should have the hybrid drive DC to AC inverter cooling system flushed, drained and filled at least once in their useful service life. This is part of the factory scheduled maintenance, and, even if it were not, any service to the inverter or inverter cooling system will require this service to be completed.

If any of the mentioned symptoms are noted, the cooling system will be checked for leaks, and, if any are found, not only will the leak be repaired, but the system will be flushed and refilled. However, if no leaks are found and the coolant level is correct, the system may be flushed as a diagnostic step. Finally, no diagnosis is normally needed to flush the system because it is a factory scheduled maintenance item. The only symptom necessary is mileage.

Flushing the hybrid inverter cooling system is much the same as flushing the engine cooling system, except there are fewer components to deal with, and the components are typically more accessible. Chemicals are introduced into the hybrid inverter cooling system through the fill port, and the system is ran. Afterwards, the system is drained, purged of old coolant, and the drain plug is replaced. Finally, the system is filled and purged of air.

RepairPal always recommends following the factory scheduled maintenance plan when servicing a vehicle. If the service mileage or time has elapsed without the service being performed, have it done next time the vehicle is in for service, or make a specific appointment. completing all services on time will reduce the likelihood of inverter cooling system failure and hybrid inverter overheating.

Not all hybrid vehicles require cooling systems for the hybrid inverter. Some do not become hot enough to need cooling, and others are cooled by fans only. It is important to understand which system your vehicle uses to prevent fraudulent services from being performed or billed.

This is something the average DIY can accomplish, but only if the system is completely understood. It is not identical to an engine cooling system, but the flush, drain, and refill procedures are very closely related. If the proper instructions are available in the service manual, the proper coolant and flushing chemicals are on hand, and the used coolant can be recycled, this can be done by the DIY mechanic.