Usage:
3512 ( 49Y, 50Y, 51Y, 24Z, 3YF ),
3516 ( 27Z, 28Z, 29Z, 25Z, 4XF, 9KF, 71Z, 72Z, 73Z ) Engines;
785 ( 8GB ),
789 ( 9ZC ) Trucks
- SUPPLEMENT: 10/22/90
SERVICE MAGAZINE; SEPTEMBER 24, 1990; PAGE 14; "Add Bolt Dampers To Oil Pump Mounting Bolts To Prevent Bolt Failures" on 3512 (49Y, 50Y, 51Y, 24Z, 3YF), 3516 (27Z, 28Z, 29Z, 25Z, 4XF, 9KF, 71Z, 72Z, 73Z) Engines; 785 (8GB), 789 (9ZC) Trucks. On Illustration 2, the counterbore diameter for the three holes is not correct. The correct counterbore diameter is 17.50 + 0.40 - 0.15 mm (.689 + .015 - .006").
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PROBLEM: The 4S5882 Bolts that hold the engine oil pump in place may fail at the oil pump-to-adapter joint. The cause of the failure is bolt shank vibration.
SOLUTION: A change to add bolt dampers to the oil pump bolts is forthcoming. In the interim, the bolt dampers can be added using the following method.
1. Modify the three mounting holes in the oil pump body as shown in Illustrations 1 and 2.
Illustration 1. Location of three mounting bolt holes in oil pump body to be modified.
Illustration 2. Section A-A. Dimensions for modifing three bolt holes for installation of 9M4355 Dampers.
2. Obtain three 9M4355 Dampers and install them in the modified mounting holes in the oil pump body.
3. Install the pump using three 4S5882 Bolts. Tighten the bolts to the standard torque.