TM  55-2840-241-23 (1)  Remove  th  lockwire  from  the  pressure  regu- lator. (2) Using a wrench, turn guide (14) clockwise to increase pressure; counterclockwise  to decrease. Ad- just the regulator until oil pressure is within limits of step d. One turn will change oil pressure approximately 13 psig. NOTE An approximate starting adjustment can be made by bottoming guide (14); then backing out 5 1/2 turns. (3)  Lockwire  guide  (14)  after  adjustment  to  pre- vent movement in either direction. 5-27. Oil Filter Housing a. Removal. (1) Remove eight self-locking nuts (7, figure 5-11) and washer (8). (2) Lift housing (9) out of the gearbox. Discard gasket (10). (3) Remove check valve (12). Discard preformed packing (11 and 13). (4) Remove preformed packing (19 and 20) from oil tubes (21 and 22) and discard preformed packing. b. Installation. (1) Lubricate new preformed packing (19 and 20) with oil (item 7 or 8, table 2-2) and install on oil tubes (21 and 22). (2) Lubricate new preformed packing (11 and 13) with oil (item 7 or 8, table 2-2) and install on check valve (12). Install the check valve in the gearbox. (3) Place new gasket (10) in the gearbox. (4) Insert housing (9) into the gearbox and engage the mounting studs. Ensure that the housing is mated with oil tubes (21 and 22) and with check valve (12). (5) Retain the oil filter housing with eight washer (8) and self-locking nuts (7). Tighten the nuts to 35-40 in. lb. 5-28. Internal Oil Check Valve The internal oil check valve (12, figure 5-11) is located under the oil filter housing (9), inside the gear- box. It serves to prevent oil from draining out of the oil tank and into the gearbox while the engine is shut down. a.  Removal.  (Refer  to  paragraph  5-27a.) b. Cleaning. Clean the internal check valve by flush- ing with solvent (item 3, table 2-2) and air dry. c.  Installation.  (Refer  to  paragraph  5-27b.) 5-29. External Oil Check Valve. The external oil check valve (4, figure 5-12) is located in the oil supply tube to the turbine. It serves to prevent oil from draining into the turbine bearing cavities while the engine is shut down. a.  Removal. (1) Remove self-locking nut (5) and bolt (1) that secure clamps (2 and 3) together. (2) Loosen the two oil tube coupling nuts and remove check valve (4) from the engine. b. Cleaning. Clean the external check valve by flush- ing with solvent (item 3, table 2-2) and air dry. c.  Deleted. d. Installation. To prevent oil starvation of turbine bear- ings, be sure the check valve is installed with the end marked "OUT" and the arrow pointing toward the rear of the engine. (1) Install check valve (4) on the pressure oil tube with the hex end marked "OUT" and the arrow pointing toward the rear of the engine. Tighten the coupling nuts to 80-120 in. lb. (2) Secure clamps (2 and 3) together with bolt (1) and nut (5). Tighten the nut to 35-40 in. lb. 5-30.  External  Sump  Pump. a. Removal. Remove two bolts (14) holding the scavenge oil exter- nal sump (15) to the firewall shield. Remove sump. Dis- card  preformed  packing  (6). b. Installation. Install  preformed  packing  (16)  in  the  seal  groove  of the power turbine support scavenge oil opening. Apply a light coat of sealer (Permatex 1372W, NSN 8030-00-599-7753)  over  the  preformed  packing.  Posi- tion sump (15) on the firewall shield. Apply Never Seez (item 26, table 2-2) to two bolts (14) and install. Tighten bolt to 35-40 in-lbs and secure with lockwire (item 10, table 2-2). 5-20 Change  18