Can Moisture be absorbed through brake fluid cap?

[xdarkxfirex]

I clean my engine bay with water every so often. I've done it for years with no issues.

A few months ago I replaced the brake fluid with Lucas dot 4. I couldn't get the back bleeders out so I managed to get as much fluid as I can out of the resevior and front bleeders.

I used one of those pen led fluid level, which gives me inaccurate readings.

I plan on buying a better reader but is it possible for water to get in through the vent valve on the cap?