What Causes the Sound of Water Sloshing When Braking?
2 Answers
The reasons for hearing a water sloshing sound when applying the brakes are as follows: 1. The sound of circulating water from the water pump. This is a normal phenomenon. 2. Water inside the car. During rain, water can flow into the door through gaps in the glass. However, doors have drainage holes, so normally there shouldn't be any water. 3. Some car brands have a heater core inside the vehicle, and when the antifreeze level is low, a water flow sound may occur. 4. A vacuum booster pump is leaking air. 5. Water ingress in the right side rail. Clearing the drainage holes under the right side rail can resolve this issue. 6. It might be the sound of gasoline sloshing inside the fuel tank.
I used to encounter this sound when driving my old car—water sloshing around when braking, which was quite annoying. Later, I learned that the most common cause is water accumulation inside the door. There are small drainage holes at the bottom of the door designed to drain rainwater, but if the car isn’t driven for a long time or is parked under trees, those holes can easily get clogged with mud or leaves, trapping water inside the door panel. When braking, the water sloshes and makes noise. If not cleaned promptly, prolonged water buildup can corrode internal door components or affect window operation, leading to bigger issues. I recommend going to a repair shop soon to have the drainage holes cleared, or you can use a thin wire to poke them open yourself—it’s safe and easy. Also, try to avoid parking under trees or in damp corners to reduce the chances of this happening.
