Water Sloshing Sound in Car When Driving: Causes and Fixes

Water sloshing sound in car when driving is usually caused by water or air getting trapped in your car’s cooling system, drains, and heater. Then, you begin to hear the noises.

Water Sloshing Sound in Car

This article explains the various reasons why your car is making a sloshing sound and the different ways to fix the problem.

Why Does Your Car Makes Sloshing Sounds?

Your car makes sloshing sounds probably because air is trapped inside your cooling system and you have a low level of coolant. Aside from these, other reasons for this sound are the presence of water in your elevator drain or your windscreen, AC, or sunroof drains are clogged.

  • Air Trapped Inside the Cooling System

Air getting trapped inside your cooling system is a major reason your car makes splashing sounds. The water sounds are caused by air bubbles moving through the coolant as your car accelerates, decelerates, or turns because the fluid is not properly circulating through your regulator to the engine.

It is easy to know If your car’s cooling system has air trapped inside. You may notice signs such as the engine overheating, frequent coolant top-ups, gurgling sounds, poor heater performance, or coolant leaks under the car. Take note of these signs accompanied by the splashing sounds.

When the air gets trapped inside your car’s cooling system, it can cause a variety of issues, including overheating, reduced performance, and splashing sounds. You must check and repair the cooling system as soon as possible to prevent further damage to the engine.

  • Low Level of Coolant

When you are low on coolant, you may hear a splashing sound from beneath the dashboard when the engine is running. These sounds serve as a warning about the state of your coolant levels. The sound is usually loudest the moment you start your engine and reduces as you keep driving.

Car Makes Sloshing Sounds

The coolant and antifreeze are designed to keep your car heated. When the coolant level in your car’s engine drops, however, air can get trapped in the cooling system. The trapped air can lead to air bubble formation, causing a gurgling or splashing sound as it moves through the system.

To know if you’re low on coolant, simply check the coolant level. Open your hood and examine the coolant reservoir. If it is below the minimum level, your car is running low on coolant. Hence, the reason why you are hearing the water splashing sounds.

  • Evaporator Drain Contains Water

The splashing sounds in your car could also occur when water is logged in your evaporator drain for a while. When the air conditioner in your car is turned on, condensation forms along the evaporator coil and drips into a condensate drain pan, which then drips under the vehicle.

Water will build up in the pan and slosh when the car is driving if the drain is blocked or not draining properly. The build-up then causes the water splashing sounds that can be particularly noticeable when the car accelerates or turns, causing the water to move around more.
  • Blocked Windscreen Drain and Water Build Up

The water splashing sounds coming from your car could sometimes result from a clogged windscreen drain. If you’re driving and you start hearing water sounds coming from the front or behind the dashboard, it may result from a clogged windshield drain in the cowl or the firewall area.

The clogging could lead to a water build-up. If too much water builds up in the cowl region, it may leak inside the car, causing mustiness and microbial development in the carpeting and upholstery. The floorboard will rust through from the inside if this occurs frequently.

  • Clogged Air Conditioner Drain

A clogged AC drain can also cause water splashing sounds in your car. When the AC drain is clogged, water cannot properly drain from the AC system, causing it to accumulate in the AC unit. As you start driving, you hear the water splash around.

  • Malfunctioning Heater Core

Another possible reason why your car may make the splashing sound could be that you have a faulty heater. If this is the case, you may be hearing the water sound under your car’s dashboard. The heater can be faulty even if your coolant level is normal.

If the heater is leaking or has a crack, coolant can leak into the car’s cabin and cause a sloshing sound as it moves around. Additionally, if the coolant level is low, air pockets can form in the heater core and generate a similar sound.

  • Worn or Rusted Sunroof Drains

Worn-out sunroof drains can also cause water-splashing sounds in your car. Sunroof drains are designed to channel water away from the sunroof and down the car, preventing water from entering. The drains can become clogged with debris, causing water to accumulate and create a splashing sound when driving.

You should check for obvious signs to confirm that you have a worn-out sunroof drain. These signs include water stains or wet spots on your car’s headliner or interior trim, a musty or moldy smell, and water accumulation in the foot Wells.

  • Clogged Car Door Drains

Another common reason you hear a water sound coming from your car is that your doors are clogged. It’s very easy for water to get logged in your car doors when it rains or while washing the car. Water can also slip inside the doors through the window seals.

Dirt and debris accumulate over time and clog the doors if the water drains from the car don’t let them out through the openings. When this happens, you will start hearing splashing sounds in your car when you are driving, particularly when stopping or accelerating.

To know if your doors are clogged, park your car to check. Open the doors and quickly swing them back and forth. If you hear a splashing noise, the door is clogged, and water has accumulated inside.

How To Stop Your Car From Making a Water Sloshing Sound

You can stop your car from making a water sloshing sound by unclogging the affected areas, such as the windscreen drains, AC drains, or other drains. You can also drain the water from the evaporator and refill the coolant to stop the sound of water sloshing.

  • Clean Up and Unclog the Drain Holes

To unclog the drain holes and get rid of the mold and mildew growth, you first need to locate the affected drain hole. Check out the different locations of drain holes in your car, including the bottom of the car doors, near the wheel wells, and under the hood.

Once you’ve found the drain holes, clean the area around them with a wire, soft-bristled brush, or cloth to remove dirt or debris. Next, use a pipe cleaner or flexible wire to dislodge debris or clogs inside the drain holes.

Fix Water Sloshing Sound

Push the pipe cleaner or wire in and out of the holes until the water flows freely. If the water is still not flowing, repeat the process until the drain holes are completely unclogged. After unclogging the drain holes, flush them with water using a hose to remove any remaining debris. Once the water is flowing freely, dry the area around the drain hole with a towel to prevent water damage or rust in the car.

  • Unclog the Air Conditioner Drain

To unclog the air conditioning drain in your car, you must first park on a level surface. Then, clear the clog with a metal wire. Prepare the wire by cutting it to a length of about 12 inches and making a hook on one end of it.

Next, locate the tiny rubber hose of the AC drain underneath your engine and carefully cut it off. You should avoid yanking on the tube to prevent further damage to the AC drain. Once the rubber hose is cut, gently attach the hook without exerting too much pressure.

After clearing the obstruction and re-tubbing the rubber hose back to the AC drain, allow the water to drain out to be sure that you have successfully unclogged the AC drain. Next, test drive your vehicle to ensure the AC drain is functioning properly.

  • Drain the Water in the Evaporator Drain

To release water from the evaporator drain in your car, first, park the car on a level surface. Then locate the drain and remove the drain plug. The evaporator drain is typically located near the firewall on the car’s passenger side and looks like a small rubber hose.

After finding the drain, ensure that the car is parked so that water can flow out easily. Next, remove the drain plug using pliers or your fingers and let the water drain out. After the water has drained out, replace the drain plug and tighten it.

  • Top Up the Coolant

When topping up the coolant, start by cooling down the engine before attempting to open the radiator cap or coolant reservoir. Check the coolant level by looking for the minimum and maximum marks on the container. If the coolant level is low, unscrew the cap on the coolant reservoir.

Next, pour in the coolant until it reaches the maximum level. If the coolant is very low, you may need to add more directly to the radiator. Once you’ve added the coolant, start the engine and let it run for a few minutes to distribute the coolant throughout the engine.

  • Repair the Heater Core

When fixing a clogged heater, you should first disconnect the heater hoses from the heater and use a garden hose to flush it out. Place the hose in one of the hose connections and turn the water on. This process will help clear the impurities built up.

While trying to unclog the heater, ensure that you allow the water to flow through the heater until it runs clear. Then repeat the process with the other hose connection. You might not get the desired result after one try, but you don’t need to worry.

All you need to do is keep flushing till it frees up. Reconnect the heater hoses to the heater and refill the cooling system with coolant. Start the engine to check for leaks. If flushing the heater does not work, try to replace the heater.


– Is It Safe to Drive With Your Car Making a Splashing Sound?

No, it’s not safe to drive with your car making a splashing sound. The sound of water splashing is a clear indication that at least one part of your car is clogged or water-logged. Driving without fixing the issue can cause further complications in your car.

Repairing the Heater Core

What Could Cause Water Sloshing Sound in the Car?

The solutions for rattling noise when driving can help address the issue of water sloshing sound in your car. This peculiar noise may be caused by water trapped in the car’s interior, typically due to clogged drain holes or a malfunctioning HVAC system. Regularly cleaning drain holes and checking the HVAC system can prevent water accumulation and eliminate the sloshing sound.

Can the Water Sloshing Sound in My Car be Caused by a Sputtering Engine?

If you hear the water sloshing sound in your car, it may not be directly caused by a sputtering engine. Car sputtering causes and fixes can vary, but the sloshing sound is usually attributed to a clogged or damaged heater core. It’s best to seek professional assistance to diagnose and resolve the issue promptly.


Now that you know what makes those water-splashing noises in your car when driving, you no longer have to worry about the sounds.

Here’s a quick summary of what we’ve discussed in this article:

  • The water splashing sounds are mostly due to clogged drain surfaces such as the AC drains, elevator, and sunroof drains.
  • Running low on coolant is another major cause of the water-sloshing noises you hear while driving.
  • The most common way to fix the water-splashing sounds you hear in your car is by unclogging the affected areas.
  • Sometimes, you may have to replace the affected parts if you can’t clean and drain them out.
  • When you hear water sounds in your car, you should immediately look for clogging signs and check your coolant level.

You now know the different factors that cause the water splashing sounds in your car and how to identify and fix each problem.

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