Prius cooling: engine and inverter water pumps

One loop cools the engine and the other cools the inverter and motors, each with its own electric or belt-driven pump. A failed inverter pump can trigger a cascade of hybrid warnings that look far more expensive than a pump.

What owners notice

A coolant warning, an overheating gauge, hybrid system warnings that seem unrelated, weak cabin heat, or coolant on the ground. On hybrids, an engine that runs in short bursts can hide a cooling problem until a long drive.

What the shops check first

Which loop is involved: the engine loop or the separate loop for the hybrid electronics. Then pump operation, leaks, the coolant's condition and level, and the sensors that report temperature, since a wrong reading can trigger the same warnings as real heat.

What the repair usually involves

Water pumps, electric coolant pumps, valves, thermostats, hoses and sensors, followed by a careful bleed. Hybrid loops trap air easily, and the shops verify flow and temperatures on a road test before the car goes home.

What the shops' records show

The count at the top of this report is every repair order matching this problem across the EV Partners shops, recounted from their Shop-Ware records whenever they sync. Below it, each shop that has done this work shows its own share, the model years it saw and what it did, with a link to its own write-up where one exists.