CORE AS-HYDRAULIC OIL COOLER 2343032 - Caterpillar

Section 4
Table 6
Proper summary of facts gathered articulate most likely root cause of failure. Additional steps/limiting information is also articulated. The Root Cause:Utilizing the facts made available to Caterpillar, the clear cause of this failure was insufficient torque on the lock nut for the #7 injector rocker arm adjusting screw. The broken injector hold-down bolt, plus the failure of the #7 injector and the #7 cylinder head are collateral damage.The root cause would be how this locknut became loose, at the time of this report, the root cause has not yet been determined. This is due to the limited information supplied to Caterpillar by the ABC Co. maintenance division, who confirmed that the valve lash and injector height had been verified, two weeks prior to the final failure.If Bill’s Service Corp. had incorrectly torqued the locknut for the #7 injector rocker arm adjustment screw, the ABC Co. verification of the injector adjustments may have revealed this issue. If this injector height was adjusted by ABC Co., then the locknut in question was improperly torqued by the ABC Co. technician.Further investigation is required.Section 5
Table 7
Conclusion of root cause clearly stated. Dealer contact/reference information provided for further questions/requests. Summary of repairs included. Summary:Additional photos available upon request.Bill's Service Corp. readjusted the #7 injector height when the engine had 0-1 hour. This fact indicates that there was no manufacturer defect in material or workmanship involved in the root cause of failure.Repair Process: Cylinder head replaced with new injector and properly torqued/adjusted.Investigation Completed By:Joe Marine
Cat Dealer
Technical CommunicatorPhotos
Illustration 1 g06098816
Valve cover from cylinder # 7, ventilated by the injector solenoid. Red circle at the right of the photo shows where the locknut of the injector rocker arm adjustment screw contacted the valve cover, while backing out of the rocker arm.
Illustration 2 g06098819
Valve cover removed, the injector was loose and injector solenoid was badly pounded. Locknut on injector rocker arm adjustment screw was loose, and this adjustment screw had backed out as high as could possibly go.
Illustration 3 g06098813
Injector #7 and related parts.
Illustration 4 g06098835
Injector #7 rocker arm, upper surface of adjustment screw locknut fretting inside the valve cover.
Illustration 5 g06098839
Injector pushrod gouged out underside of the rocker arm after the adjustment screw backed out as far as possibly could.
Illustration 6 g06098866
The loose injector damaged underside of injector rocker arm.
Illustration 7 g06098891
Spalling on injector rocker arm foot, damaged after the adjustment screw backed out and the clearance between this foot and the injector became excessive.
Illustration 8 g06098894
Broken injector #7 hold-down bolt with detached head, stress fatigue fracture.
Illustration 9 g06098898
Head of injector hold-down bolt. The red arrows point to bolt some of the multiple ratchet marks which indicate high stress.
Illustration 10 g06098901
Contact damage to cylinder head # 7, caused by the loose injector. The remaining threaded section of injector hold-down bolt still in the head.