How to Fix Sloshing Sound in Car [4 Common Causes Explained]

Water pouring into your automobile means this water is somewhere it shouldn't be. Ignoring this symptom will have consequences.

Chances are high that soon you'll get mold and a musty odor inside your car. Moreover, water can affect electrical components and create corrosion.

Below we'll answer your "Why does my car sound like water sloshing?" question. In a few words, this happens due to:

• Clogged AC evaporator drain
• Dirty door drain
• Blocked windshield drain
• Air in the cooling system.

Read on to learn more about each problem and find out how to fix the sloshing sound in a car.

4 Reasons why you hear the liquid sloshing when starting your car

No matter where it appears, you can't leave unattended water pouring inside your car. But to understand how you can fix the problem, knowing the possible reasons is essential.

Clogged AC evaporator drain

A dirty drain pipe is the most common reason you hear the liquid sloshing in your car when you start it. And first, let's briefly check how the AC system works.

The air conditioner gets the air from outside and takes it to the evaporator — a small radiator inside the dashboard. A refrigerant absorbs the heat of the air changing its state from liquid to gaseous or — evaporating.

During this process, the water (condensate) from the hot air appears on the evaporator, and dry cold air enters the cabin. The condensate, in its turn, is directed to the drain pipe, which takes the liquid out of the vehicle.

Since air cooling continues as your AC works, the volume of the generated water is significant. And when it can't evacuate, it remains in the air cooling system.

That's when you hear the water sloshing sound behind the dash, especially when you turn, accelerate, or break. In this case, the problem is with the clogged drain valve. And sometimes, this water can get under the front passenger's floor mat.

How to fix

A professional mechanic will clean the evaporator drain quickly and effectively. However, if you're ready for a bit of discomfort, try to do that on your own.

First, you need to find the AC drain pipe under your car. It's often located under the front passenger's seat or between the two front seats.

Once done, place the air gun connected to a compressor into the drain pipe and blow the air inside. Make sure to move aside, as the water will gush out shortly.

Use a flexible wire or thin drain brush if you don't have an air compressor. Wiggle it well to remove grime deposits, and be ready to keep your face away from the pipe when doing this.

Dirty door drain, torn membrane, or damaged seal

Typically, cars should be fearless of water, whether they face heavy rain, snow, or tunnel car wash. Though no vehicle is waterproof, its drain system helps remove water from the vehicle's surface.

All liquids that fall on your car in the door area get to the door drainage channels. These channels end up with openings that allow the water to evacuate.

But since these holes are pretty small, they can quickly get cluttered with debris. This way, water gets blocked inside, producing a sloshing sound as you drive.

However, the situation can worsen if the door's inner membrane is torn. The same applies to the around-the-door and window-sides rubber seal is damaged.

Then water can not only splash around but reach cords and provoke corrosion of mechanisms.

How to fix

The remedy for the door drains is the same as clogged AC drains. You'll need to blow compressed air or insert a flexible wire into the hole. The stagnant water must promptly splash out.

However, cleaning the drains won't be enough if water gets inside the door panels. You'll need professional help to spot and reach the problem area. You may also need to remove mold and musty smell.

Blocked sunroof and windshield drain pipes

The sunroof also can cause a water sloshing sound in your car as its seal isn't waterproof. You can hear the noise from above and even see leaks when parking on a slope.

Usually, water goes through the channels along the sunroof perimeter to reach its corners. From there, it gets to the drain pipes through the A-pillar and gets to the door drains.

Once any of these exits is clogged, water gets captured and moves around.

Windshield drains can also get blocked with leaves, pine needles, and dirt, allowing water to pour into the front of your car.

How to fix

Car service specialists will help you retrieve debris and stale water from the effluent pipes. They'll also fight against stuffy odor.

However, you can also try doing it yourself with an air compressor or a long wire. Just open the sunroof or front doors, locate the drain holes, and blow air or push the wire inside.

Air in the cooling system

Another liquid that can sound like water sloshing is coolant (or antifreeze). This happens only when air gets into the cooling system.

The mixture goes through isolated lines from the coolant bottle to the engine cylinders. As the liquid reaches engine cylinders, it absorbs the produced heat. Then it moves to the radiator, cools there, and returns to the engine.

Any air entering this hermetic system creates the coolant to pour, producing the sloshing sound.

But in addition to the irritating noise, the air in the cooling system can lead to corrosion of its elements and engine overheating.

How to fix

The common reason for air getting into the antifreeze is its low level in the bottle. So ensure to add enough coolant and keep its level above the minimum.

Also, air can get in if you fail to fix the antifreeze bottle cap properly. This cap enables pressure control in the entire cooling system. This way, it helps increase the boiling point of the coolant and, thus, take more heat away from your engine.

So arrange your cooling system maintenance with a mechanic unless you feel confident about draining the radiator and adding new antifreeze or "bleeding" the radiator yourself.

To sum it up

The sound of pouring water in your car can appear because of clogged drains of the AC evaporator, windshield, sunroof, or doors. Also, the sloshing noise is provoked by air getting into the cooling system.

You can solve any of these problems independently or engage car repair professionals.