Sloshing Sound Under Dash

Question

I have a 2011 Suzuki SX4 Crossover AWD with MT. Sometimes when I start it up, begin moving forward, or quickly decelerate I can hear what sounds like water (or some other liquid) moving from one place to another (can't quite tell where) under the dash or maybe just behind the firewall. I took it to the Suzuki service center (almost 2 hour drive from my home), and they told me that the A/C coolant was low. They refilled it and sent me on my way. However, I still hear the sloshing sound behind the dash. Does anyone have any ideas on what this might be? Thanks.

ADDITIONAL INFO

I've recently noticed that when this "running water" sound occurs that it is more prominent when the engine is running faster (e.g. during acceleration). This leads me to believe maybe this has something to do with the water pump, or some other liquid pump, that is run by the engine and not moving enough liquid to fill the pipe, hence a sloshing / running water sound.

Answer 1

Your AC drain may be stopped up. Your AC evaporator condenses water when the warm moist air passes over it, this happens in the normal operation of the AC. There is a drain that is suppose to drain the water outside the car, when it gets stopped up water collects in the evaporator case under the dash, it will eventually drain somewhere, most likely on your carpet inside the car, in the mean time you will be able to hear it sloshing around.

Look under you hood, or from the underside of the car for a rubber tube sticking out of the firewall, you can unplug it with a coat hanger, or piece of wire.

The picture below may be what you have, if not it will at least give you an idea of what you are looking for.

Picture Source

Answer 2

My experience (in multiple cars, albeit not your make/model) has been that this sound always means your cooling system is under-filled. If you've emptied your cooling system and refilled it, it can be really hard to get all the air pockets out of the heater core, especially since in many vehicles it's almost as high as the radiator cap and at the opposite end of the system. The best system I know of is to park on a steep grade with the front of the car facing upward, then let the engine run with the radiator cap off. Squeezing the hoses, especially the hoses near the back of the engine compartment that go to the heater core, and varying the throttle can help. You should get bubbles coming up the top of the radiator. Whenever the fluid level drops, add some more coolant, and repeat until you can't get any more bubbling.

By the way, another symptom that might indicate this is your problem is that it's usually associated with poor heater performance (taking a long time to get heat, or only getting warm air, not hot air, out of the heater).

Answer 3

Some cars have a grille just forward of your w/screen. If so, remove the access drain tubes inside plenum chamber to far left and right. Usually it takes a child size hand to reach, so you can insert a hose and flush. Good move is to lift floor coverings first. Don't forget to check weep holes under your doors either.