AD 77-09-08

77-09-08 DETROIT DIESEL ALLISON: Amendment 39-2889 as revised by Amendment 39-2907. Applies to 250-C20, C20B, C20C, B17, B17B engines. Compliance required within the next 30 calendar days after the effective date of this AD, unless already accomplished. To prevent engine power loss resulting from bleed valve diaphragm failure, accomplish the following: Clip lockwire and remove the exit nozzle P/N 6874818 from the bleed valve cover. Using a small screwdriver install strainer assembly P/N 6896347 in the valve cover exit port until it is fully seated. Install the exit nozzle in the bleed valve cover. Tighten to 35-45 lb. in. CAUTION: DO NOT EXCEED 45 LB. IN.; OVERTIGHTENING MAY DAMAGE THE STRAINER. Approximately 2-3 threads of the exit nozzle will be visible when the strainer assembly is seated fully in the bleed valve. If more than three threads are visible this modification must not be accomplished and bleed valve must be removed for overhaul. To clear the bleed valvecover passages of burrs and other particles, again remove the exit nozzle and strainer assembly from the valve cover. With the throttle at IDLE CUT OFF, motor the engine in excess of 10% rpm. Using a small screwdriver, reinstall the strainer in the valve cover exit port until it is fully seated. Reinstall the exit nozzle in the bleed valve cover. Tighten to 35-45 lb. in. CAUTION: DO NOT EXCEED 45 LB. IN.; OVERTIGHTENING MAY DAMAGE THE STRAINER. Approximately 2-3 threads of the exit nozzle will be visible when the strainer is fully seated in the bleed valve. Secure the exit nozzle with lockwire. (Detroit Diesel Allison Commercial Engine Bulletins No. 1116 for the 250-C20 series and No. 1071 for the 250-B17 series engines also pertain to this subject.) Amendment 39-2889 became effective June 10, 1977. This amendment 39-2907 becomes effective July 18, 1977.