Can the Trunk Vent Be Blocked?
4 Answers
It is best not to block the trunk vent. Here are the specific functions of the trunk vent: 1. Pressure relief: When forcefully and quickly closing the door or trunk, air is forced into the car. If the interior space is completely sealed, this closing action will increase the air pressure inside, making it difficult to close the door or even preventing it from sealing properly. With a vent, when the interior pressure rises, the vent opens to release the pressure. 2. Air circulation: When driving with the windows closed and the air conditioning on, if the air conditioning is set to external circulation, outside air is continuously drawn into the car. Without this vent, the air pressure inside the car would keep increasing, eventually preventing outside air from entering the car.
Last time my dog knocked over dog food in the trunk, the vent was half blocked. As a result, on rainy days the windows were completely fogged up and I couldn’t see the road at all. This thing is actually a balance vent for air exchange between the inside and outside of the car. If it’s completely blocked, not only will it cause fogging, but your ears will also feel painful when closing the door. Some older cars even have their AC airflow reduced by half because the vents are completely blocked. When modifying the audio system, never cover it with soundproofing cotton. If you really need to block it temporarily, choose a breathable material. I remember once a clump of leaves got washed into it during a car wash, and the trunk always had a muddy smell. After searching for a long time, I found it was due to fermented debris in the vent—you really can’t underestimate these two small grids.
Last week, I helped my neighbor clean out her trunk. She had blocked the air vents with a blanket, saying she was afraid dust would get in. As a result, every time she opened the trunk on rainy days, there was a musty smell, and the defogging function of the AC became slower. These inconspicuous vents are actually the breathing channels of the car cabin, balancing internal and external air pressure. Blocking them makes the car door close with a loud 'bang' because the air has nowhere to escape. Some cars make strange noises when going over speed bumps, mostly because the plastic flaps of the vents are stuck. When changing a spare tire, remember to look down there—it’s easy for leaves and mud to accumulate, but never seal them with tape, or the trunk can get as hot as 50 degrees in summer.
In my 20 years of car repair, the most outrageous thing I've seen was someone using chewing gum to block the vents to prevent mice, only to end up driving in heavy rain feeling like in a sauna. These two coin-sized mesh openings are precisely calculated ventilation ports by the car manufacturer; blocking them disrupts the internal air pressure balance. During summer, obstructing them hinders proper air conditioning circulation, while in winter, it can easily cause rear window frosting. Especially for cars with sunroofs, blocking the vents and opening the sunroof creates a loud suction noise. High-pressure car wash jets won't damage these vents; instead, they help clear debris and prevent clogging. For dust prevention, regularly vacuum the mesh, but never seal them shut.
