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TM 55-1930-208-24
4-15. CRANKSHAFT AND SEALS - Continued.
c. Inspection Continued.
(5) Carefully inspect the rear end of the crankshaft in the area of the oil seal contact surface for evidence of a
rough or grooved condition. Any imperfections of the oil seal contact surface will result in oil leakage at this
point.
(6) Slight ridges on the crankshaft oil seal contact surface may be cleaned up with emerycloth (item 7, Appendix
C) and crocus cloth (item 5, Appendix C) in the same manner as detailed for the crankshaft journals. If the
crankshaft cannot be cleaned up satisfactorily, replace the crankshaft.
(7) Check the crankshaft thrust surfaces for excessive wear or grooving. If only slightly worn, the surfaces may be
dressed with a stone. Otherwise it will be necessary to replace the crankshaft.
(8) Check the oil pump drive gear and the crankshaft timing gear for worn or chipped teeth. Replace thegears, if
necessary.
(9) Check the crankshaft dowel extension. Current dowels extend 1/2 inch from the crankshaft while former
dowels extend 5/8 inch.
(10) Carefully check the crankshaft for cracks which start at an oil hole at an angle of 450 and follow the journal
surface at axis. Any crankshaft with such cracks must be rejected. Several methods of determining the
presence of minute cracks not visible to the eye are magnetic particle, fluorescent magnetic particle, and
fluorescent penetrant.
(11) Inspection of the crankshaft using magnetic particle method, magnetize the crankshaft, then cover the
crankshaft with a fine magnetic powder or solution. Flaws, such as cracks, form a small local magnetic which
causes the magnetic particles to gather there, effectively marking the crack. The crankshaft must be de-
magnetized after completion of test.
(12) Inspection of crankshaft using fluorescent magnetic particle method. This method is similar to magnetic
particle method, but it is more sensitive since it employs magnetic particles which are fluorescent and glow
under "black light". Very fine cracks that may be missed under the first method, especially on discolored or
dark surfaces, will be disclosed under "black light".
(13) Support the crankshaft on its front and rear journals on V-blocks or in a lathe and check the alignment at the
adjacent intermediate main journals with a dial indicator.
4-64

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