Have a question about the Coolant Transfer Pump on my 2007 Prius. When turning the car off, does that pump operate every single time? Should it make the “whirring†sound every single time you turn the car off? I always notice the sound, and I noticed that the last time I shut the car down, there was no noise. I can’t remember ever NOT hearing the pump, but I am not sure if it is normal or not for it to not operate on a given shutdown….. Will listen again at next shutdown... Thanks
When turning the car off, does that pump operate every single time? Should it make the “whirring†sound every single time you turn the car off? No, a computer decides depending the various temperatures it receives in the cooling system as to whether to run the pump. I've read those parameters somewhere on the net, or this forum, but don't recall them.
The coolant heat recovery pump is a good example of the complexity of the hybrid system. The valve that controls flow of coolant between the engine cylinder head, the coolant canister and the heater core has three positions. One position allows coolant flow between the cylinder head and the canister. Another position allows coolant flow between the cylinder head and the heater core. A third position allows coolant to flow from the cylinder head to both the canister and the heater core. Hence, as you are driving along when the engine is at normal operating temp, hot coolant may be flowing into the canister. Or it may not. If the coolant in the canister is sufficiently hot, then there's no need for the pump to run when the car is made IG-OFF. If you are in the garage five hours after the car is made IG-OFF, you may hear the coolant heat recovery pump running for a few seconds. The purpose of this is to allow the engine ECU to assess the temp of stored coolant, and if the temp is substantially lower than the temp of the coolant when it entered the canister, a DTC will be logged. If you would like to learn more, go to Automotive Training and Resource Site and find the Hybrid12 Engine Control System.pdf file within the Technical Articles section.
