07 Prius: Which Direction Does Coolant Flow Through Heater Core?

Follow the hoses. One connects the core to a small electric pump near the firewall, which further connects to a three-way valve. The two branches from the three-way valve connect to the cylinder head and to the thermos. That heater core connection is the one where coolant flows into the heater core.

The other connects back toward the engine thermostat bypass nipple, on a route where it also has connections to the throttle body and the electric pump next to the thermos. That is the connection for coolant flowing out of the core and back toward the thermostat bypass.

 

There's this diagram that shows the coolant hoses.

Actually, I think that diagram is incorrect, as I would expect coolant to flow out the side nipple on the heater electric pump toward the core. Then flow should be from the core toward the thermostat area on the engine block.

I guess that "to-from" the heater sounds better than "from-to"?



Posted via the PriusChat mobile app.

 

Yeah, the arrows in that diagram look wrong. Two of 'em, anyway; they got FRONT right.

At least, it doesn't match another diagram with arrows, in the gen 2 New Car Features manual. That shows, as you'd expect, the "water pump (for heater)" pumping into the heater core, and the return from the core in the hose that returns to the thermostat bypass.