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
