What is the water leaking from under the car?
4 Answers
Reasons for water dripping under the car: 1. Condensation forming water droplets: If it occurs after using the air conditioning for a while, this is a normal phenomenon. It happens because during air conditioning operation, moisture in the cabin condenses on the evaporator, forming water droplets that are then discharged outside the car through the drain pan and drain pipe; 2. Loss of antifreeze: Check if the antifreeze in the radiator is low. If it is, promptly visit a 4S shop to inspect the cooling system for faults. Water dripping from the muffler and exhaust pipe at the rear of the car is also normal, commonly seen in winter. Gasoline injected into the cylinders mixes with air and, after complete combustion in the combustion chamber, mainly produces carbon dioxide and water. The water, at high temperatures, is discharged into the atmosphere in the form of water vapor.
I just noticed a puddle of water under my car after parking, which happens quite often. It's very common to see water dripping from the chassis after driving in summer, mostly due to air conditioning condensate. The white water stains feel clean to the touch, so it's normal and nothing to worry about. However, once I saw sticky greenish fluid with a slightly sweet smell, and it turned out to be leaking coolant when I took it to the repair shop—ended up replacing an aged hose. In winter, clear water droplets from the exhaust pipe are actually a good sign, indicating efficient engine combustion. As long as it's not red transmission fluid or black engine oil leaking, small puddles near the tires aren't a big deal; brake discs may also seep water after rain or car washes. Of course, the safest approach is to crouch down and check the exact dripping location and color.
With over 20 years of car repair experience, I often encounter panicked owners pointing at water stains under their vehicles. Most times, it's just condensation from the AC—clear, odorless, and dripping below the passenger-side aluminum pipe. Here's a simple test: after turning off the engine, place a white tissue at the drip spot. AC water leaves plain wet marks; if it's light green or pink with a sticky feel, it might be coolant leakage. A gasoline smell warrants immediate inspection of fuel tanks and lines. Pay special attention to foamy, pale-yellow liquid under the engine—this likely indicates brake fluid leakage, a serious safety hazard. New drivers should keep some test strips at home—they're quite handy.
Last week after washing my car, I noticed water on the ground again, so I specifically researched the differences between leaks in different locations. Water dripping from the middle of the engine compartment is usually air conditioning drainage, clear like purified water. Water dripping from the exhaust pipe at the rear is condensation from combustion-produced water vapor, with a slight sulfur smell being normal. Thick orange-red fluid dripping near the rear wheels is most likely transmission fluid leakage. Blue-green oily substance leaking below the front bumper probably indicates a cracked windshield washer fluid reservoir. The most dangerous scenario is brown oil stains seeping near the oil pan - in this case, immediately turn off the engine and call for a tow truck, as continuing to drive may damage the engine.
