To anyone inclined to chime in: My '09 Prius has recently started to create an interesting sound from the engine compartment right after I park and shut it down. Scenario: Temps here in AZ have been very high - typically 108. After driving for an hour or so with the AC on (of course), when I shut the car down and get out I hear the coolant storage pump come on for a half-minute or so then go off (normal), but then I hear a very low-level hissing-groaning sound (not a sharp hissing, but a hissing sound with a bunch of bass note in it), that almost that gives me the impression of coolant slowly moving somewhere within the system. This sound continues for a couple minutes and as time passes, it slowly decrease in amplitude until it completely stops. I definately do not have an external leak where I'm loosing coolant because the resovour tank level hasn't dropped. And one more thing: it didn't do this when the temps were cooler, and I likely think it will go away when temps cool off again in the fall. Just curious if anyone else has noticed this.
Yes, I also hear this sound in hot weather with my 2004. It sounds almost like plumbing in a cheap apartment building when someone is taking a shower - a squeaky sound. I replaced the radiator cap but that didn't help. Since the cold coolant level is not dropping, I decided to ignore the sound.
Not the inverter. Since the noise has only occurred when it was quite hot, I figure it might be sound of steam inside the sytem. After all, if some of the coolant is pumped into the holding tank when you shut down, the level in the engine block must drop a bit and when you shut the engine down it is quite hot and maybe generating steam? Just curious if other noticed this and/or what their take on it was.
FWIW... I 'just' drove home from dealership (25 miles, 82 degrees out with AC on) with my new 2011 Prius and it did the same thing. Hopped on the computer for a bit and searched here for info on this hissing sound, walked back out to garage about 30 min later and it has stopped. Am I complaining? Nope... who cares... I got 54-55 mpg with cruise set to 65 mph on highway on my way home!!!!
I have had same concern and after taking car to dealership was told that it was the inverter coolant pump circulating coolant to cool down inverter motor similar to a fan motor cooling down engine after car has been shut off
This noise is the freon in the air conditioner that is still circulating.It last a long time after car is shut off (approximately up to5 minutes). But only occures if the air conditioner has been running.The longer the air conditioner was running the longer the hiss/whistle/girgle lasts but not longer than 4 or 5 minutes.With the fan still on (air compressor off) you will notice this circulating freon is still generating cool air for the 4 to 5 minute period , but not cold air in the latter minutes.just slightly cool.
