TM 10-6640-215-13 Table 2-1.  Operator Preventive Maintenance Checks and Services Item Interval Item To Check Procedure Not Fully Mission No. Service Capable If: d.  Observe drive belts for Drive belts are loose or cracks, slippage, or binding cracked. caused by excessive looseness or tightness of belt.  Proper drive- belt deflection should be 3/4 in- ches under moderate thumb pressure. e.  Drain moisture tray as re- quired during operation. 9 Before Air Tank and Sys- Drain air tank as required during tem Piping operation. 10 Before Vacuum Pump a.  Check for loose mounting Missing mounting bolts. bolts. b.  Check crankcase oil level. Low oil level. c.  Check intake filters for ob- Clogged or dirty filters. structions. d.  Observe drive belts for Drive belts are loose or cracks, slippage, or binding cracked. caused by excessive looseness or tightness of belt.  Proper drive- belt deflection should be 3/4 In- ches under moderate thumb pressure. a.  Check for loose mounting Missing mounting bolts. bolts. b.  Check crankcase oil level. Low oil level. c.  Check Intake filters for ob- Clogged or dirty filters. structions. d.  Observe drive belts for Drive belts are loose or cracks, slippage, or binding cracked. caused by excessive looseness or tightness of belt.  Proper drive- belt deflection should be 3/4 in- ches under moderate thumb pressure. 11 Before Water Pump, a.  Check for loose mounting Missing mounting bolts. Valves, and bolts. Piping b.  Check water piping in me- Class III leaks detected. chanical and laboratory compart- ments for signs of leakage. 2-33