TM 10-3930-671-24 Table 3-1.  Unit Preventive Maintenance Checks and Services - CONT. Mo-Months Hr-Hours Item Interval Item to be Inspected No. Mo Hr Procedure If NBC exposure is suspected, all air filter media should be handled by personnel wearing protective equipment.   Consult your unit NBC Officer or NBC NCO for appropriate handling or disposal procedures. 15 3 500 Air Cleaner/Intake System Inspect air cleaner element (Appendix F, Engine Air Cleaner, Section 4.9).  Tighten or replace parts as necessary to make sure air intake system does not leak (i.e.  cracked hoses, loose clamps, punctures, etc.). 16 3 500 Hydraulic Tank Breather Replace hydraulic tank breather (Appendix F, Planned Maintenance Procedures, Section 3.2). 17 3 500 Engine Check/tighten valve cover bolts (Para 5-16).  Check/ adjust valve tappet clearance (Appendix F, Valve Clearance Adjustment, Section 4.5). 18 6 1000 Cooling System Cooling System Test cooling system protection level with hydrometer test (Appendix F, Cooling System, Section 4.8). Remove all jewelry such as rings, dog tags, bracelets, etc.  If jewelry contacts battery terminal, a direct short may result in instant heating of tools, damage to equipment, and injury or death to personnel. 19 6 1000 Batteries Clean/tighten batteries and cables (Para 3-27, Battery Cable Service). 20 6 1000 Gauges, Indicators Inspect wire harness (Appendix F, Electrical System Wiring, Section 6.1). 21 6 1000 Transmission Drain and fill transmission (Appendix E, Lubrication Order, and Appendix F, Planned Maintenance Procedures, Section 3.2). 3-10