70-50-01
LEAKAGE
CHECKS
Cylinder leakage is broken down into two areas of concern, the "Static Seal" and the "Dynam-
ic Seal".
Static Seal
The static seal consists of the valve to valve seat seals, spark plug to spark plug port seals
and cylinder head to barrel seal (Ref. Figure 70-50-02). No leakage of the static seal is
permissible.
Dynamic Seal
The dynamic seal consists of the piston rings to the cylinder wal seal (Ref. Figure 70-50-02).
This seal leakage can vary from engine to engine by the cylinder displacement, cylinder choke,
ring end gap and piston design.
70-50-02 EQUIPMENT
Testing equipment must be kept clean and checked periodically for accuracy as follows:
Using a line pressure of
100 to 120 p.s.i., close the cylinder pressure valve, then set the
regulator pressure valve to 80
p.s.i. The pressure in both gages should stabilize with no
leakage.
The restrictor orifice dimension in the differential pressure tester (Figure 70-50-03) for
Teledyne Continental aircraft engines must be 0.040 inch orifice diameter,
0.250 inch long
with
60" approach angle, and must flow 120
2
cubic feet per hour at 30 p.s.i. differential
pressure.
Master Orifice
Tool
For conformity /in tester equipment, a Master Orifice Tool has been developed to calibrate
equipment and determine the low indicated leakage limit prior to the engine leakage check.
Connect compressed air at 100-120
p.s.i. to the tester with cylinder pressure valve closed.
Turn the regulator pressure valve on, adjusting pressure to indicate 80
p.s.i. Remove the dust
caps from both ends of the Master Orifice Tool and install onto the cylinder spark plug
adapter. Turn the cylinder pressure valve on and readjust regulator pressure gage to read 80
p.s.i. At this time, the cylinder pressure gage indication will be the
low
allowable limit for
cylinder leak checks.
The low allowable limit is referred to as the master orifice calibrated
pressure reading. After the master orifice calibrated pressure reading has been
recorded,
close regulator pressure valve and remove Master Orifice Tool from the cylinder adapter.
A schematic diagram of a typical differential pressure tester is shown in Figure 70-50-03.
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