As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THERE IS A STRONG OILY SMELL IN THE COCKPIT ONCE THE APU IS RUNNING AND THE BLEED AIR IS SELECTED ON. FOUND BOTH WATER SEPARATOR FILTER SOCKS DIRTY. CLEANED FILTER AND FOUND COCKPIT WATER SEPARATOR VALVE STUCK OPEN. CLEANED AND LUBED VALVE. RE-INSTALLED WATER SEPARATOR TO INSTALL ORIGINAL CONFIG. PERFORMED ENGINE RUN, OPS CHECKS GOOD IAW CE-750 MM 21-10-00.