Damp carpet or a wet boot area is the main giveaway on the W176. You might also notice a musty smell inside the cabin. It happens because the rear vent flap seal degrades over time — water tracks in through the housing behind the rear bumper. Often gets mistaken for a more serious leak but it's usually just the flap seal gone.
The rear vent flaps on the W176 are a known weak point. Over time the seal degrades and water tracks in through the housing into the boot area — it's often mistaken for a more serious leak. If the seal has failed the full flap assembly typically needs replacing. A qualified Mercedes specialist should confirm the source before any parts are ordered
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Water leaks can have multiple causes. If interior dampness or water ingress is present the vehicle should be inspected by a Mercedes-Benz dealer or qualified specialist before parts are ordered.