Generally, the drain holes in vehicles are located in the following areas: the front windshield area of the engine compartment, the four corners inside the sunroof, the lower part of the front and rear doors, inside the fuel tank cap, at the bottom of the spare tire in the trunk, and the gaps between the front and rear headlights and the body fenders. Among these, the drain holes in the engine compartment and sunroof are the most prone to clogging. More detailed information is as follows: 1. Engine compartment drain holes: These are typically located on both sides of the front windshield wipers, usually one on each side. The engine compartment is a relatively open environment, so wastewater and debris can flow into it along the windshield. Engineers have designed a water barrier at the rear of the engine compartment, near the lower edge of the windshield, and placed drain holes in this barrier. Among the interior drain holes, those in the engine compartment are the most likely to clog. They are also close to the air conditioning intake, making it easy for bacteria to grow in the hot and humid engine compartment. In severe cases, water can even flow into the car through the air conditioning intake. Additionally, in some models, the engine control unit (ECU) is located here, and if it gets wet, it can cause unexpected engine malfunctions. 2. Sunroof drain holes: These are located at the four corners of the sunroof. Even when the sunroof is closed, rainwater can seep into the car through the gaps. Modern vehicles are designed with water channels that direct rainwater from the sunroof to the front and rear drain holes, which then route the water through the A-pillars or C-pillars and out from under the car. Unless both drain holes on either side are clogged simultaneously, water accumulation in the sunroof is rare. 3. Door drain holes: These are located at the lower part of the door panel, usually with at least two per door. Most car models do not have separate drainage pipes inside the doors; instead, rainwater flows directly through the rust-proofed door panel and exits through the drain holes. If these drain holes are clogged, water trapped inside the door panel can damage the window regulator, speakers, and central locking system. Many drivers report hearing sloshing sounds while driving, which are often caused by water trapped inside the door panels. 4. Fuel tank cap drain: The fuel filler opening on most vehicles faces upward, making it prone to water accumulation at the lower part. In some cities, dust and sand can enter through the gaps around the fuel tank cap and accumulate there. If this drain hole is blocked, it can also lead to water accumulation. 5. Trunk drain holes: Under normal circumstances, the trunk does not easily take in water. Rainwater that seeps into the trunk is usually drained through channels near the taillights and exits near the rear fenders. In extreme situations, such as when the car is submerged, the trunk drain holes may need to be manually opened to quickly drain the water. Depending on the vehicle, there are usually 1-2 trunk drain holes. Since these are rarely used, manufacturers often seal them, and they can be unscrewed or punctured when needed.
