Sloshing sound...Prius 2006. Conducted research but no solution

Unfortunately, further "research" or investigation is your only avenue.
I've owned cars/trucks where drain plugs...usually located in the bottom of the doors have plugged up and I started hearing "sloshing"....but once it started it was constant, in other words did not go away with driving...and it certainly wasn't behind the dash.

I'd be "concerned" but not alarmed. If you can get it to replicate, the quickest avenue to discovery might be a drive to a service center.

But "sloshing" that appears-then disappears has me stumped.

Once you track it down...let us know what it was.

 

It is probably the rain gutter which runs under the windscreen. It has an outlet on one side only, and as I read it gets clogged with leaves, etc. such that one hears the sloshing that you describe when turning. Open the hood and remove the plastic cover with the grating to get at it.

 

I agree that the cowl tray that houses the windshield wiper motor is the likely source of the sloshing sound due to trapped water. There are two drains: one on each end of the tray.

It is necessary to unbolt and remove the windshield wiper arms first. Then two plastic fasteners on the ends of the black plastic cover can be removed and the two cover pieces can be lifted out.

 

+1 on the wiper tray. My cover was off and there were a bunch of leaves in there, the drains Patrick mentioned could easily become clogged, see pic.

A good write up: PCV replacement how-to with photos | PriusChat

 

Have you had any recent repairs?

 

You should be checking coolant level and check it cold at the radiator cap. When the cooland is low and the engine first starts you hear coolant and air circulate through the heater core. I have had this on other vehicles.

 

What Glen wrote was what I was trying to get at. It is particularly difficult to get all the air out of the cooling system on the Prius when repairs are done to it; it only needs to be down a little to give you that "sloshing" sound, from air in the heater core.
Try running down the highway with the heater on econ and full hot for a period of time and then re-check the level in the bottle.

 

I bought my first Prius a few weeks ago and have noticed the same thing on a couple of occasions. In my case it has only happened after the car has been standing in rain so I'm certain the problem is not engine or cooling system related. I'm sure it's water in that area down below the windshield. You'll probably notice that like mine if you weave as you go down the street that it will dump the water out on the road after a couple of weaves and the problem will go away until next time it rains. I figured it was a blockage up there somewhere, guess I'll do some poking around this weekend and see if there's a blockage.