What was found
OIL ODOR IN THE COCKPIT, DURING CLIMB THRU 18,000 FT, A STRONG EXHAUST, OIL ODOR FILLED THE AIRPLANE. THE ODOR LASTED A FEW MINUTES AND CAME AND WENT THRU DURATION OF SHORT FLIGHT. APU WAS OFF. WHEN APU WAS STARTED ON THE GROUND THERE WAS A SURGING AND CYCLING NOISE POSSIBLY FROM ACM OUTSIDE AIRCRAFT AND A KNOCKING NOISE FROM AFT CLOSET INSIDE AIRCRAFT. REMOVED AND REPLACED THE ACM IAW MM 21-51-00, OPS CHECKED NORMAL. REMOVED AND REPLACED THE WATER SEPARATOR IAW MM 21-21-003, OPS CHECKED NORMAL.