TM 5-3895-383-24 7. Engine runs too hot: If coolant temperature is too high, pressure will be high  enough  to  move  the  cap  off  of  the  sealing surface   in   the   radiator   and   cause   coolant   loss through  the  overflow  tube.    See  Problem  No.  26, Above Normal Coolant Temperature. 8. Expansion tank too small: The  expansion  tank  can  be  either  a  part  of  the radiator  or  it  can  be  installed  separately  from  the radiator.  The expansion tank must be large enough to hold the expansion of the coolant as it gets warm or has sudden changes in pressure.  Make sure the expansion tank is installed correctly, and the size is according to the recommendations of the OEM. 9. Cylinder  head  gasket  leakage,  or  crack(s)  in  cylinder head or cylinder block: Remove   the   radiator   cap   and   with   the   engine running look for air bubbles in the coolant.  Bubbles in the coolant are a sign of probable leakage at the head  gasket.    Remove  the  cylinder  head  from  the engine.    Check  the  cylinder  head,  cylinder  walls and  head  gasket  surface  of  the  cylinder  block  for cracks.  When installing the head, use a new head gasket.    Tighten  the  bolts  that  hold  the  cylinder head according to the Specifications Section of the Service Manual. C.  Internal Leakage Probable Cause(s): 10. Erosion or crack(s) in injector sleeves: If fuel is detected in the coolant, a possible cause is a  defective  injector  sleeve.    Remove  the  injectors and  inspect  the  sleeves  for  cavitation  erosion  or cracks.  Replace any defective sleeves. 11. Cylinder head gasket leakage: If the cylinder head  gasket  leaks  between  a  water passage    and    an    opening    into    the    crankcase, coolant will get into the crankcase. 12. Crack(s) in cylinder head: Crack(s) in the upper surface of the cylinder head, or   an   area   between   a   water   passage   and   an opening into the crankcase, can allow coolant to get into the crankcase. 13. Crack(s) in cylinder block: Crack(s)   in   the   cylinder   block   between   a   water passage and the crankcase will let coolant get into the crankcase. Problem 37:  Air Inlet Heater (If Equipped) Probable Cause(s): Heater Stays On Longer Than Allotted Time - Any Cycle Heater Does Not Come On System Check Lamp Test Pre-Heat Cycle Crank Heat Cycle Regular Heat/Run Cycle Heater Element Check Coolant Sensor Check Oil Pressure Switch Check 1. Heater stays on longer than allotted time-any cycle: Replace   the   air   inlet   heater   control   module   (if equipped). NOTE: Cycle times are approximate only.  Some variance does not necessarily indicate a system failure. 2. Heater does not come on: Check for the following: a detective heater control module. a detective oil pressure switch (regular heat cycle only). a defective coolant sensor. a defective heater element. a detective power relay (magnetic switch). To  avoid  personal  injury  (burns,  make  sure  the  coolant temperature is below 37.8°C (100°F) before performing any tests. NOTE: Air Inlet Heater (AIH) controls and wiring may be different for various engine applications.  Refer to electrical   information   and   Parts   book   for   the particular application. Problem 38:  Soot In The Inlet Manifold Probable Cause: 1. On  diesel  engines  a  small  amount  of  soot  is  normal. This is due to the design characteristics of the engine. Valve  overlap  allows  the  intake  to  open  slightly  before the exhaust stroke has been completed, which will allow some soot to be pushed into the inlet manifold. 6-54