I believe the valve is two way. Let's air in and out, but not liquids.
I could be wrong though as I have never bothered to take a vent apart.
I can say when I have had issues it was with dirt caked older saws.
The only saw I currently have is an MS260 and it doesnt leak a drop, despite being stored in my shed that gets pretty hot. I have never cleaned the vent on it either, but have always kept it clean. It's a bit of a cherry that really only cuts a few cord per year and an odd tree job or three.
I could be wrong though as I have never bothered to take a vent apart.
I can say when I have had issues it was with dirt caked older saws.
The only saw I currently have is an MS260 and it doesnt leak a drop, despite being stored in my shed that gets pretty hot. I have never cleaned the vent on it either, but have always kept it clean. It's a bit of a cherry that really only cuts a few cord per year and an odd tree job or three.