Question about coolant pump

It doesn't seem worth a special trip. The worst that would happen is loss of the engine heat that would otherwise be stored. But watch carefully for any other signs of trouble, for example a coolant leak.

 

Yeah, it freaked me out once too when the pump didn't come on. I think it might pump it into the thermos occasionally when driving and engine is hot... maybe to preheat it? If it hasn't been too long since its done that it won't pump upon shutoff. This car's too darn smart for the average person to figure out. It might be changing it's behavior because it's getting hotter this time of year too.

 

I agree with abq sfr. kimgh, I think your car is operating normally.​

I've attached an excerpt from the diagnostics section of the 2005 repair manual regarding the coolant heat recovery system (p. 05-274):​

"This system uses an electric pump to supply hot coolant stored in the coolant heat storage tank into the cylinder head of the engine, in order to optimize engine starting combustion and reduce the amount of unburned gas that is discharged while the engine is started. Before the engine starts, the ECM operates the electric water pump to direct the hot coolant in the heat storage tank into the engine, in order to heat the cylinder head (this process is called ”preheat mode”). The duration of the operation of the electric water pump is variable, depending on the temperature of the cylinder head. During the normal operation of the engine, the water valve opens the passage between the cylinder head and the heater and closes the passage between the cylinder head and the tank. During preheat mode in which the cylinder head is heated, the water valve opens the passage between the tank and the cylinder head, in order to allow the coolant to flow from the tank to the cylinder head. At this time, in order to warm up the intake port quickly before the engine is started, the coolant flows in the reverse direction.
The sensor for the system, which is provided at the tank outlet, is constructed similarly to the engine coolant temperature sensor and is connected to the ECM. The CHS tank outlet temperature sensor has a built in thermistor, whose resistance varies with the coolant temperature."​

 

OK, then how about an excerpt from the 2004 New Car Features manual (see pages EG-30 and EG-31). This excerpt indicates that hot coolant can be stored into the storage canister during driving. However if insufficient hot coolant is stored during driving, then the pump will run when the car is shut down:

4) Storage Operation (During Driving)​

After the engine warm-up has been completed, the ECM operates the water valve to switch the engine coolant passages, in order to send the hot coolant heated by the engine into the heater core (for the heater) and the coolant heat storage tank (for storing the hot coolant).

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During the storage operation, the coolant heat storage water pump is in a stop, thus the engine coolant is circulated by the mechanical water pump driven by the engine.

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Once the coolant heat storage tank is filled with hot coolant, the ECM switches the coolant passages by operating the water valve (provides the same water valve position as that of the engine warm-up operation), and stops the storage operation.

5) Storage Operation (IG-OFF)
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If the power switch has been turned OFF (IG-OFF) before the recovery of the hot coolant has been completed during driving, the ECM actuates the coolant heat storage water pump and operates the water valve to switch the engine coolant passages, in order to store the hot coolant into the coolant heat storage tank. However, this operation will not be done if the engine warm-up is insufficient.This operation stops after it continues for several seconds.

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