These boot / cabin vents ( when incorrectly installed or faulty ) can allow water to enter into boot space, this can be a common problem across many manufacturers.
The plastic frame of the vent assembly can becoming distorted.
I will include a couple of photo’s of a relatives Ford Focus, that had been badly affected by this problem.
Customer complained of a stale smell in the car and that it was constantly fogging up the glass.
There was SO much water in the boot, it then started to migrate into rear carpet area !.
The fix was to install new vents and ensure they were correctly seated.
This vents are usually located behind the rear bumper cover and are sited in the rear quarter of each side of the car.
I will try and find a video that displays the issue on the Focus.
I think the MG will have a similar method of providing a cabin / boot vent quickly.
These vents have a one way plastic flap valve system arrangement, that allows the trapped air inside of the car to escape, when the large hatchback lid is closed down shut.
Sometimes you can hear the flaps allowing air to escape, as the hatchback lid is closed down quickly.
It’s rare the plastic flaps themselves are the direct problem, it’s the frames themselves that are not fitted or sealed correctly to the body shell.
In the video, you can see how the rain water leaves the roof and is then directed down the gutters of the hatchback, then it travels behind the rear bumper cover.
It then flows directly down to the boot vent location, on each side of the car.
If these vents are incorrectly installed, or the frame of the vents are distorted.
This how water ingress is allowed to enter the boot space.
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