REPAIRING THE ENGINE FRAME OR BLOCK Some engine block repairs are cost efficient, while others  are  not.  The  following  paragraphs  briefly  discuss basic repairs to the block itself. Later paragraphs discuss repairs to block components. LEAKING WATER JACKET Most engine blocks that have a leaking water jacket are not worth the cost to repair. To determine if such a block   can   be   repaired   economically,   consult   the appropriate  MILSTD  and  technical  manuals  for  the engine. WARPED CYLINDER BLOCK OR CRANKCASE  FLANGES You may use a hand surface grinder to correct small amounts of surface warpage. Do not remove more metal than  necessary.  The  manufacturer’s  manual  will  specify how much metal you may remove with the hand grinder. If the warpage exceeds the maximum allowed for hand grinding,   send   the   block   to   the   machine   shop   for machine  grinding. WORN BOLT HOLES Over  a  period  of  time,  bolt  holes  may  become oversize due to wear from threading and unthreading the fasteners. You may correct a worn bolt problem by one of three primary methods, depending on the situation. 1.   If the bolt hole is slightly oversize, you may be able to simply use a larger bolt in the hole, if such use is authorized for the component the bolt fastens down. 2.  If  enough  metal  remains  around  the  hole,  you may  be  able  to  install  a  helicoil.  Check  the  helicoil installation   instructions   and   appropriate   technical manuals  to  determine  whether  or  not  a  helicoil  is acceptable. 3. You may also till the hole with weld metal and then drill and tap a new hole. Whatever method you use to correct the problem, always check the bolt and bolt hole for proper fit. INSPECTING, TESTING, AND REPAIRING CYLINDER LINERS Cylinder   liners   may   become   damaged   or   worn excessively.  The  following  paragraphs  discuss  the  more common causes and repairs. CRACKED, BROKEN, AND DISTORTED LINERS You  should  suspect  one  or  more  cylinder  liners whenever you notice one of the following indications: l Excessive water in the lubricating oil l   An   accumulation   of   water   in   one   or   more cylinders of a secured engine l   An abnormal loss of water in the cooling system l  High  cooling  water  temperature  or  fluctuating pressure (caused by combustion gases blowing into the water jacket) l Oil in the cooling water When  you  suspect  that  a  liner  is  cracked,  try  to locate the cracks visually. If you cannot locate the cracks visually, use another testing method, such as the water pressure  test  or  air  pressure  test  described  earlier.  To check  liners  with  integral  cooling  passages,  plug  the outlets  and  fill  the  passages  with  glycol-type  antifreeze. This liquid will leak from even the smallest cracks. Cracks in dry liners may be more difficult to locate because there is no liquid to leak through the cracks. You may need to use magnaflux equipment or penetrating dye to locate these cracks. Causes Cylinder liners may crack because of poor cooling, improper fit of piston or pistons, incorrect installation, foreign bodies in the combustion space, or erosion and corrosion.  Improper  cooling,  which  generally  results from restricted cooling passages, may cause hot spots in the liners, resulting in liner failure due to thermal stress. Scale formation on the cooling passage surfaces of liners may also cause hot spots; wet liners are subject to scale formation. You may remove the scale by following the procedures outlined in chapter 233 of the Naval Ships’ Technical Manual (NSTM). Proper cooling of dry liners requires clean contact surfaces  between  the  liners  and  the  cylinder  block. Particles of dirt between these surfaces cause air spaces, which are poor conductors of heat. Films of oil or grease on these mating surfaces also resist the flow of heat. Distortion, wear, or breakage may result if a liner is not  properly  seated.  Causes  of  improper  liner  seating may be metal chips, nicks, or burrs, or improper fillets, In  figure  3-3  an  improper  fillet  on  the  cylinder  deck prevents the liner from seating properly. To correct an 3-3