water tank, connect air line, and apply
30 to 40 psi (207 to 276 kPa) air
pressure. Submerge head in water
deep enough to cover entire head.
(c) Check carefully around valve seats and
injector sleeve for cracks. Discard head
(d) Test cylinder head for leaks at 75 to 85
psi (517 to 686 kPa) water pressure with
water at 17a to 200F (79 to 93 C).
Check carefully around valve seats and
injector sleeves for cracks even though
such cracks may not show water
leakage. Discard head if cracked.
(e) Open water outlet of test fixture; check
cylinder head. If restriction is evident,
remove all pipe plugs and fuse plugs;
clean water jackets of salt, lime, or
THE USE OF ACID IS EXTREMELY
INJURIOUS TO MACHINER. ALWAYS
PROVIDE A TANK OF STRONG SODA
WATER AS A NEUTRALIZING AGENT.
(f) Clean fuel passage with a brush and
flush passages with solvent to remove
(g) Check water passage running full length
of head between valves for restrictions.
If plugged, open by rodding or drilling.
(h) Check lubricating oil restrictor plug and
lubricating oil passages to be sure they
(plugged fuel passages).
(j) Block fuel outlet and attach an air
(k) Install air fittings in fuel inlets and apply
air pressure of 90 to 100 psi (620 to 689
(l) Close air inlet valve and inspect
passage for leaks.
Check air gauge; there must be
no drop in pressure for 15 seconds;
discard an unserviceable head.
(3) Cylinder heads are equipped with fuse plugs
containing a metal-alloy center that melts if
the engine is over- heated. Examine fuse
plug for signs of overheating. If fuse plug
has melted, check carefully for further
damage to head and engine, and proceed
(a) Drill through center of melted plug.
(b) Tap hole with left-handed threads.
(c) Insert a screw and turn until plug breaks
loose; remove screw and melted plug.
(d) Install new fuse plug.
(4) Check for loose valve seat inserts by lightly
tapping head near inserts. A slight
looseness may be found by tapping when
head is cold and covered with film of oil.
(5) If seat area width exceeds 0.125 inch (3.18
mm) at any point and cannot be narrowed
sufficiently, it is unlikely that seat can be
(6) Note results of hydrostatic test. Leaks
indicate need for replacement of injector