Our extractor (Neff)has been making a horrible noise and the cover is a bit precariously balanced. It just fell down so I decided to give it a clean before putting it back up. The absorbent bit is made of metal mesh and is still brownish after a clean. Does it now need replacing and if so how often and where would I get a replacement ? Or is there a magic way to remove the grease. Tips on getting it to run quieter appreciated too.