coolant valve cycling on and off?

I've got the identical noise in my 2005. The dealer replaced the inverter coolant pump and the noise became much less frequent. My scanguage came up with a P1121 trouble code a few times since and this was attributed to the coolant recycle valve. Perhaps these two conditions are related. In any event the coolant valve is not a critical item and replacement can be safely postponed.

 

I have been hearing a similar noise recently. My car is fast approaching 100,000 miles (since new in Jan. 2006). I had a check engine light around 60,000 and the inverter collant pump and coolant were changed under warranty. I didn't hear the noise until maybe a month ago. It sounds just like the thermos tank cycling when the car is off. I do mostly highway driving, and have noticed that it may be related to touching the brake pedal, but I've heard it other times , i.e. not on the brakes. Is it the coolant pump maybe failing again? I haven't seen any warning lights. I have a scangage; will pushing the "scan" button tell me anything? Thanks for any info.

 

I had the identical problem. The solution was replacement of the coolant control valve. Total cost 504.00 Cad. See my posts under "Mysterious noise" and "Big-Bad-Toyota"

 

I've heard it many times. It only happens after I put the car in "B" going down steep hills and the battery is low. (purple) it sounds like the car is hyperventilating. I can't upload a file it doesn't work.

 

The noise you are hearing in B mode is the engine being revved by mg1 as a method of braking. This should not be used when the battery is low on charge as you are wasting the regen energy and hence fuel lowering your MPG. Using the brakes in D mode will recharge the battery, saving fuel, and will not use or overheat the normal disc (rotor) brakes.
To the OP this noise could be the often overlooked pump motor that circulates the hot coolant from the engine to the heater core "needed for the heater to work when the engine is not running to transfer hot coolant from the engine to the heater".

John (Britprius)