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WARNING
Care must be exercised in opening the
cylinder pressure valve, since sufficient air
pressure will be built up in the cylinder
causing it to rotate the crankshaft if the
piston is not at top dead center. The propeller
must be secured during check to prevent
rotation.
(4) Open the cylinder pressure valve completely.
Check the regulator pressure gauge and adjust, if
necessary to 80 pounds per square inch.
(5) Observe the pressure indication on the cylinder
pressure gauge. The difference between this
pressure and the pressure shown by the regulator
pressure gauge is the amount of leakage through
the cylinder. If the cylinder pressure gauge
reading is higher than the previously determined
master orifice calibrated pressure reading,
proceed to the next cylinder and perform leak
check. If the cylinder pressure gauge reading is
lower, proceed with the following:
NOTE...
Document cylinder compression pressure.
Static Seal Check( See Figure 16-6, "Static Seal.")
(6) First check the static seal for leakage. Positive
identification of static seal leakage is possible by
listening for air flow sound at the exhaust or
induction system port. When checking for
cylinder head to barrel leakage, use a soapy
solution at the cooling jacket to barrel junction
and watch for bubbles. Use a soapy solution
around both spark plug seals for leakage. NO
LEAKAGE
IS
SEALS.
(7) If leakage is occurring in the intake or exhaust
valve areas, try staking the valves. Remove
rocker covers from applicable cylinder. Place a
fiber drift on the rocker arm directly over the
valve stem and tap the drift several times with a
hammer to dislodge any debris that may be
between the valve face and seat. If leakage by
the valves cannot be corrected by, "staking," the
cylinder must be removed for repair or
replacement.
ALLOWED
IN
STATIC
CAUTION
When correcting a low reading in this manner,
rotate the propeller so the piston will not be at top
dead center. This is necessary to prevent the valve
from striking the top of the piston in some engines.
Rotate the propeller again before rechecking
leakage to reset the valves in the normal manner. Do
not allow the fiber drift to contact the valve spring
retainer or rotocoil.
(8) If leakage is noted between the cylinder head
and barrel, REPLACE THE CYLINDER, (See
Figure 16-7, "Dynamic Seal.")
(9) To check the dynamic seal of a cylinder, proceed
with the leakage test and observe the pressure
indication of the cylinder pressure gauge. The
difference between this pressure and the
pressure shown by the regulator gauge is the
amount of leakage at the dynamic seal.
WARNING
To prevent possibility of serious bodily injury
or death, before moving the propeller
accomplish the following:
a. Disconnect all spark plug leads.
b. Verify
magneto
connected to magnetos, that they are
in the "OFF" Position and "P" leads
are grounded.
c. Throttle position "CLOSED."
d. Mixture control "IDLE-CUT-OFF."
e. Set brakes and block aircraft wheels.
Insure that aircraft tie-downs are
installed and verify that the cabin
door latch is open.
f. Do not stand within the arc of the
propeller blades while turning the
propeller.
(8) If the leakage is below the previously
determined low cylinder gauge reading, loss past
the dynamic seal may be due to piston ring end
gap alignment or by the piston and piston rings
Cylinders
switches
are
16-9
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