Rear Vents
All cars have rear vents hidden somewhere at the back of the car. The purpose of these vents is to release air pressure. As air comes in through the front of the car via the heater/air conditioner, or through open windows, it needs to escape through the back to prevent drag.
It should also be noted that it is important for a car to have good air circulation to help air it out, and prevent the car getting damp or smelling musty.
The vents are usually positioned behind the back bumper on the sides of the car, and almost always consist of a set of one-way flaps, rather like cat-flaps, often called gates.
These vents are a very common cause of leaks. The main cause of the failure is that each gate is a single sheet of plastic with a fold which acts both as a hinge and a spring to create a one-way valve, and over time the plastic weakens, meaning that the gates don't properly close. This makes replacement the only viable fix for this issue, thankfully these are usually inexpensive parts. As with other points of entry, it may also be the case that the gaskets for the unit perish or dirt and debris blocks the function.
It is usually necessary to remove the rear bumper to access the rear vent properly, as they are usually affixed from outside the car's body.
This also gives the opportunity to clean the entire area and gain access to any other fittings passing through the body, as these may also have rubber grommets which will have aged and may leak. Therefore, it makes sense to address these while the bumper is removed. They can be cleaned up, replaced if necessary, and refitted with sealant.
Typically, when rear vents leak, they do not flood the back of the car. Instead, water finds its way into the box sections which run along the side of the car, causing water to flow into the floor of the cabin. This will then find its way to the lowest point, which is often the front foot wells.
Written by Danny Argent. Last updated 25/10/2023 13:04