Parking Brake Valve trouble potential

[SierraYankee]

Thanks for the informative reply and relevant pages.

Can the parking brake valve (if physically damaged) cause air to be entrained in the brake lines ?
My brakes keep losing pressure and oil, and every 4th-5th landing the master cylinders need to be replenished. No oil on the floor or belly (unless it is squirting out on the runway during landings).