La Cornue’s deflector-style grease filters are held in place by a magnetic closure rather than a mechanical latch or screw. You pull them down to remove them and push them slightly upward to reinsert them, and in normal operation that magnetic hold is strong enough to keep a filter seated through ordinary vibration from the motor. A filter that sags at one corner, rattles while the hood runs, or drops down partway on its own is a sign that closure is no longer holding the way it should, and it is a separate issue from weak extraction or a heavily loaded filter.
What Weakens the Closure Over Time
Grease buildup along the frame edge where the filter meets the magnet is the most common cause, since it can hold the two surfaces slightly apart even when the magnet itself is fine. Cleaning the frame and the filter edge — not just the filter’s mesh — during a normal wash cycle addresses this before it becomes a persistent rattle. A filter that has been dropped or handled roughly can also warp its frame just enough to break full contact with the magnet, which shows up as a closure that seems to work on one side but not the other.
Testing Which Part Is the Problem
With the hood off and cool, remove the filter, clean both the filter frame and the magnetic strip it seats against, then reinsert it and check whether it now sits flush and holds firmly. If it does, the buildup was the cause. If a filter still will not seat evenly after a thorough cleaning, or visibly does not sit flush against the frame, the filter itself has likely warped and is worth replacing rather than continuing to reseat.
Why This Is Worth Fixing Promptly
A filter that is not fully seated does not just rattle; it lets some grease-laden air bypass the filter entirely on its way toward the motor and ducting, which accelerates the same grease buildup on the fan wheel that eventually shows up as vibration and reduced airflow elsewhere in the hood. Catching a loose filter early is a small fix compared with the fan wheel cleaning that follows if it is ignored.
A Loose Filter Is Also a Kitchen Hazard
A filter that drops from overhead while the range is in use, even from a short distance, lands directly above an active cooktop and any pans on it, which makes this worth addressing sooner rather than later purely for everyday safety, separate from anything to do with hood performance.
Regular Care Prevents Most of This
La Cornue’s own guidance calls for washing these filters every two to four weeks depending on how often the hood is used, which is frequent enough to keep grease from building up at the frame edge in the first place.
If a filter on your range hood will not stay seated, a La Cornue range hood repair visit checks the filter frame and its magnetic closure before assuming a bigger problem is behind it.