What is the fault when water comes out from under the car?
3 Answers
Here are three possible fault conditions: 1. Coolant reservoir leakage: The coolant reservoir is made of plastic and may become brittle and prone to cracking after several years of use. 2. Coolant level too high: If the coolant level is too high, it can easily overflow from the pressure relief valve on the reservoir cap. When adding coolant, avoid overfilling—just fill between the MAX and MIN marks. 3. Coolant hose damage: Like the reservoir, coolant hoses are made of plastic and may deteriorate over time, leading to potential leaks at connection points.
I've been driving for so many years and have seen water under the car several times. Most of the time, it's actually normal, especially when using the air conditioning in summer. The AC system produces condensation, which then drains out through a tube onto the ground—just like how an air conditioner drips water—so there's nothing to worry about. However, if the water isn't clear or has a sweet or chemical smell, it might be a coolant leak, such as from a damaged radiator or hose, which can cause the engine to overheat and, in severe cases, lead to a breakdown. In winter, after a cold start, the exhaust system also releases some water vapor, which condenses and looks like water droplets—this is also common. I recommend doing a quick check yourself: get down and see where the water is coming from—is it from the AC drain or near the front of the car? If you notice an odd smell or see white smoke from the car, take it to a repair shop immediately—don’t try to save money and risk turning a small issue into a major repair. Regularly replacing coolant and checking the AC system can help prevent problems before they arise.
As a car enthusiast who frequently tinkers with engines, I pay close attention to water leaks under the car. The most common cause is the drainage of air conditioning condensate, which is normal. However, if the water volume is large or the color appears greenish or reddish, it could indicate a cooling system leak—such as a cracked radiator or loose hose—possibly leaking antifreeze, which can corrode components and reduce cooling efficiency. Another possibility is water vapor condensation from the exhaust manifold or catalytic converter, especially during cold starts. To diagnose, park the car and wait a few minutes to observe the source of the leak, then give it a quick sniff—antifreeze has a sweet smell, while plain water is odorless. If abnormalities are detected, use a multimeter to check voltage or visit a professional shop promptly to prevent long-term engine damage from fluid leaks. Regularly maintain a clean undercarriage and frequently check the antifreeze level.
