TELEDYNE CONTINENTAL ® AIRCRAFT ENGINE CATEGORY 3

SERVICE BULLETIN SB03-3

Compliance Will Enhance Safety FAA APPROVED
SUPERSEDES M84-15

SUBJECT: DIFFERENTIAL PRESSURE TEST AND BORESCOPE INSPECTION

PROCEDURES FOR CYLINDERS.
PURPOSE: This bulletin provides differential pressure test and borescope inspection procedures for
cylinders to be used as a guide in the determination of their serviceability with respect to
these tests.
At each 100 hour interval, annual inspection or when cylinder problems are
COMPLIANCE:
suspected.

MODELS
AFFECTED: All Teledyne Continental Motors (TCM) engine models.

GENERAL
F.A.A. Advisory Circular (AC) 43.13-1. Chapter 8, Section 1, paragraph 8-1 states; “ Consult the manufacturer’s
manuals, service bulletins and instruction books regarding the repair and overhaul, inspection, installation, and
maintenance of aircraft engines, for that particular make, model and type of engine. This section lists acceptable
inspection and repair procedures that may be used in the absence of an engine manufacturer’s maintenance
information.” The following procedures are to be used as the standard for performing a cylinder differential
pressure test on all TCM engines. Reference 14 CFR Part 43.13.

A. CYLINDER CONDITION DISCUSSION

The cylinder differential pressure test has become a widely used method of assisting in determining the internal
condition of cylinders and cylinder components. As with any test or inspection the cylinder differential pressure
test has certain limitations that necessitate its use in conjunction with other non-invasive inspections. TCM
requires a cylinder borescope inspection be accomplished in conjunction with the differential pressure test.
In addition to the cylinder differential pressure test and borescope inspection, further inspection of any suspect
cylinder is recommended in accordance with the guidelines set forth in this service bulletin. Refer to Tables 1
and 2. The technician should also be cognizant of the engines’ oil consumption, the appearance or color of the
engine oil and any visual indications of high crankcase pressure (combustion blow-by) such as an oily, wet area
on the aircraft belly or lower wing surface. Refer to the latest revision of TCM’s Service Bulletin (SB) 96-12
and Service Information Directive (SID) 97-2 for additional inspection items and pilot awareness topics.
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2003 Teledyne Continental Motors, Inc.

The purpose of the cylinder differential pressure test is to IDENTIFY LEAKS and the SOURCE OF LEAKS,
with the engine under static conditions (not running), using a regulated pressure source. When performing a
cylinder differential pressure test a regulated test pressure of eighty pounds per square inch (80 PSI) is directed
into the cylinder with the piston at top dead center at the end of the compression stroke and the beginning of the
power stroke. Eighty pounds per square inch (80 PSI) is used as a test pressure for safety reasons and is
significantly less than the combustion pressure of 800 to 1000 PSI created during engine operation. Pistons,
piston rings, valves and valve seats rely on combustion forces to assist in creating a complete seal during engine
operation.
NOTE: This static leak check does not relate directly to cylinder pressures developed during actual engine
operations.
The purpose of the cylinder borescope inspection is to provide a visual method of examining the internal cylinder
components and must be used in conjunction with the differential pressure test.
Excess cylinder wall or piston ring wear, broken piston rings and burned valves will normally be evidenced by
additional conditions that must be taken into consideration when determining cylinder condition. These may
include, but may not be limited to:
Excessive cylinder barrel wear and/or piston ring wear:
1. Elevated crankcase pressure; reference the latest revision of TCM Service Bulletin M89-
9.
2. Increased oil consumption. See note | on page 9.
3. Oil becoming discolored within first 10 hours after an oil change.
4. High iron content in oil analysis may be an indication. Broken piston rings:
1. Scored, grooved cylinder wall, evident via a borescope inspection.
2. Abnormal debris in oil filter or oil screen.
3. High iron content in oil analysis may be an indication.
Burned Valves:
1. Usually results in differential leak test reading in the 0/80 to 40/80 range.
2. Easily identifiable during borescope inspection.
Additionally, many variables affect what a technician sees from a differential pressure test reading. These
variables include, but are not limited to:
1. Abnormal amounts of oil in cylinder.
2. Temperature of the engine and the uniformity of cylinder temperature at the time the differential
pressure test is performed.
3. Accuracy of the test equipment being used.
4. Capacity and pressure output of the source of compressed air and the techniques used by the
technician when performing the test.
B. CYLINDER DIFFERENTIAL PRESSURE TEST:

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(a) Required Tools and Equipment:

In addition to the standard complement of tools required to perform maintenance and repairs on aircraft engines
the following tools and equipment are required to perform a cylinder differential pressure test.

1. Source of dry, compressed air capable of providing a minimum line pressure of 125 P.S.I. with a minimum
flow capability of 15 Cubic Feet per Minute.

2. Cylinder differential pressure tester. Select one of the following units listed below or equivalent.

• Eastern Technology Corporation Model E2M{. See Figure 1. Recommended by TCM. This
differential pressure tester incorporates the Master Orifice Tool.
Eastern Technology Corporation
180 Roberts Street
East Hartford, CT 06108 Phone:
860-528-9821

• Eastern Technology Corporation Model E2A{. See Figure 2.

This differential pressure tester requires you to purchase separately the Master Orifice tool P/N
646953.
Eastern Technology Corporation
180 Roberts Street
East Hartford, CT 06108 Phone:
860-528-9821

3. Master Orifice Tool P/N 646953A.

This tool is available in limited supply.
SPX Corp. - Kent Moore Tool Division
28635 Mound Road
Warren, MI 48092
Phone: 800-345-2233

NOTE: Differential pressure test equipment must be certified and calibrated. Failure to properly maintain and
calibrate test equipment may result in false cylinder differential compression readings.
{ Eastern Technology Corporation offers calibration and repair service on these items.

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 FIGURE 1
Eastern Technology Corp. Model E2M

FIGURE 2
Eastern Technology Corp. Model E2A

(b) Establishing the Acceptable Pressure Leakage Limit:

The “Master Orifice” is a calibration standard that must be used prior to performing the cylinder differential
pressure test. The “Master Orifice” establishes the Acceptable Cylinder Pressure Leakage Limit for the
test equipment being used and the atmospheric conditions at the time of the test. The Acceptable Cylinder
Pressure Leakage Limit reading must be recorded along with the individual cylinder readings in the engine
logbook and the inspection work order.

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 1) Eastern Technology Corporation Model E2M:
This test is accomplished with no connections to the female quick connector.
a) Set the Master Orifice Valve to the OFF position; handle horizontal and directly over
the OFF label.
b) Set the Slow Fill Valve (next to the pressure regulator) to the OFF position; handle
vertical and pointing down.
c) After making sure the Slow Fill Valve is OFF, connect your air source to the tester at
the male quick connection fitting.
d) Adjust pressure regulator so left hand gauge reads 80 PSI.
e) Set the Master Orifice Valve to the TEST position; handle vertical and pointing down.
f) Open the Slow Fill Valve completely; handle horizontal and over the PRESSURIZED
label.
g) If necessary, adjust the regulator to maintain 80PSI indication on the left-hand gauge.
h) Record the pressure reading on the right hand gauge. This reading is the Minimum
Acceptable Cylinder Pressure Leakage Limit.
i) Close the Slow Fill Valve completely; handle vertical and pointing down.
j) Set the Master Orifice Valve to the OFF position; handle horizontal and directly over
the OFF label.
You are now ready to perform the cylinder differential pressure test.

2) Standard Differential Pressure Tester and Master Orifice Tool P/N 646953:

FACTORY CALIBRATED ORIFICE

DUST CAP DUST CAP

SPARK PLUG
THREADS (18mm)

FIGURE 3
MASTER ORIFICE P/N 646953
a) Make sure the Regulator Pressure Valve is backed all the way OUT.
b) Make sure the Cylinder Pressure Valve is OFF or Closed.
c) Remove the protective caps from both ends of the Master Orifice and install the Master
Orifice onto the threaded end of the cylinder adapter and tighten hand tight.

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 d) Connect the cylinder adapter with Master Orifice attached to the female quick
connection on the supply hose from the differential test unit.
e) Connect your air source to the tester at the male quick connection fitting.
f) Adjust pressure regulator so regulator pressure gauge reads 80 PSI.
g) Turn the cylinder pressure valve to the ON or OPEN position.
h) If necessary, adjust the pressure regulator to maintain a reading of 80 PSI on the
regulator pressure gauge.
i) Record the pressure reading on the cylinder pressure gauge. This reading is the
Minimum Acceptable Pressure Leakage Limit.
j) Turn the cylinder pressure valve to the CLOSED or OFF position.
k) Remove the cylinder adapter and Master Orifice from the female quick connection on
the supply hose from the differential test unit.

l) Remove the Master Orifice from the cylinder adapter.

You are now ready to perform the cylinder differential pressure test.
ADAPTER

CYLINDER
PRESSURE CYLINDER
VALVE ADAPTER CYLINDER
PRESSURE
CYLINDER VALVE
PRESSURE
GAUGE CYLINDER
PRESSURE
GAUGE

RESTRICTOR
ORIFICE
RESTRICTOR
REGULATOR ORIFICE
PRESSURE MASTER ORIFICE
GAUGE (HAND TIGHT) REGULATOR CYLINDER
PRESSURE
CYLINDER
GAUGE
Read Minimum Acceptable Cylinder
Leakage Limit on this Gauge Read Cylinder Leakage
REGULATOR on this Gauge
PRESSURE
VALVE REGULATOR
PRESSURE
VALVE
COMPRESSED
AIR SOURCE
COMPRESSED
AIR SOURCE

Establishing Minimum Acceptable

Cylinder Pressure Leakage Limit With
Performing Differential Pressure Test URE
Master Orifice Tool FIG3
FIGURE 4
Differential Pressure Test Equipment
(c) Performing The Cylinder Differential Pressure Test:
Ideally, perform the cylinder differential pressure test as soon as possible after the aircraft has been flown.
If the aircraft cannot be flown prior to performing the cylinder differential pressure test, it must be operated
on the ground, with the cowling installed until a minimum cylinder head temperature (CHT) of 300 to 350
degrees Fahrenheit is observed on the aircraft gauge. For aircraft fitted with constant speed propellers

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operate the engine at a high enough power setting to allow the cycling of the aircraft propeller. For aircraft
with fixed pitched propeller, operate the engine to full static RPM.
WARNING
Magnetos must be grounded and fuel must be shut off prior to test to make certain that the
engine cannot accidentally start. Take necessary precautions to prevent accidental rotation
of the propeller while performing the differential pressure leak test. Differential Pressure
tests are best performed with two people, one to adjust the pressure regulator and one to
hold the aircraft propeller.
NOTE: The 360 series, 470 series and 520/550 Sandcast engines utilize a starter adapter design that results
in an increased resistance in turning force when the propeller is turned in the opposite direction
of normal rotation. The technician may, if he desires, reduce the amount of resistance by
removing the starter motor from the starter adapter when performing this test.
1. Perform the test as soon as possible after the engine is shut down to ensure that the piston rings, cylinder
walls, and other engine parts are well lubricated and at operating clearance.
2. Remove the most accessible spark plug from each cylinder. Identify the cylinder number and position
of the removed spark plugs. Examination of the spark plugs will aid in diagnosing engine and cylinder
conditions. Reference spark plug manufacturers’ technical data.
3. Turn the crankshaft by hand in the direction of rotation until the piston (in the cylinder being checked)
is coming up on its compression stroke.
4. Install the cylinder adapter in the spark plug hole and connect the differential pressure tester to the
adapter. (NOTE: Cylinder pressure valve is in the CLOSED position). Slowly open the cylinder
pressure valve and pressurize the cylinder to 20 PSI.
5. Continue rotating the engine in the normal direction of rotation, against this pressure, until the piston
reaches top dead center (TDC). TDC is indicated by a sudden decrease in the force required to turn the
crankshaft. If the crankshaft is rotated too far, back up at least one-half revolution and start over again
to eliminate the effect of backlash in the valve operating mechanism and to keep the piston rings seated
on the piston ring lands.
WARNING
Care must be exercised in opening the cylinder pressure valve, since sufficient air
pressure will be built up in the cylinder to cause it to rotate the crankshaft if the piston
is not at TDC.
6. With the piston at top dead center, open the cylinder pressure valve completely. Check the regulator
pressure gauge and adjust, if necessary, to 80 PSI.
7. To assure that the piston rings are seated and the piston is square in the cylinder bore, move the propeller
slightly back and forth with a rocking motion, while applying the regulated pressure of 80 PSI, to obtain
the highest indication. Adjust the regulator as necessary to maintain a pressure gauge reading of 80
PSI.
8. Record 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.
Record individual cylinder readings as; (pressure reading)/80 PSI.
9. Note any leakage source (air discharge) and determine serviceability. Refer to Table 1.

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 10. Proceed to the next cylinder and repeat Step 3 through 9 until all cylinders have been checked.
11. After all cylinder pressure indications have been recorded, proceed with a borescope inspection of each
cylinder in accordance with Table 2, section C.

TABLE 1
DIFFERENTIAL PRESSURE TEST RESULTS
AIR DISCHARGE PRESSURE TEST VALUE SYMPTIONS AND RECOMMENDED ACTION
SOURCE OBSERVATIONS
Cylinder differential pressure Normal Borescope Indications. Continue engine in service.
Air discharge at oil test reading above leakage Oil Consumption stable, no Repeat differential pressure
filler/crankcase breather. limit. excessive oil discharge out test at next 100-hour/annual
engine breather. inspection.
Cylinder differential pressure Normal Borescope Indications. Fly Aircraft at Cruise Power
test reading below leakage Oil Consumption stable, no setting { and repeat cylinder
limit. excessive oil discharge out differential pressure test
engine breather.
Cylinder differential pressure N/A Remove cylinder for repair
test reading below leakage
limit after re-check
Air discharge at oil
filler/crankcase breather. Oil Consumption abnormal |,
Cylinder differential pressure Remove cylinder for repair
test reading above or belowwith oil discharge out engine
leakage limit. breather.
Borescope inspection reveals
heavy carbon deposits in
combustion chamber and on
piston crown with
excessive oil puddling in
cylinder barrel
TABLE 1 (continued) DIFFERENTIAL PRESSURE TEST RESULTS
AIR DISCHARGE PRESSURE TEST VALUE SYMPTIONS AND RECOMMENDED ACTION
SOURCE OBSERVATIONS
Little to no air discharge at Cylinder differential pressure Oil Consumption abnormal | Remove cylinder for repair.
oil filler/crankcase breather. test reading abnormally high with oil discharge out engine
breather.
Borescope inspection reveals
heavy carbon deposits in
combustion chamber and on
piston crown.
Excessive oil puddling in
cylinder barrel.

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Air discharge into induction Cylinder differential pressure Normal cylinder borescope Continue engine in service.
system test reading above leakage inspection results.
limit.

Cylinder differential pressure Normal cylinder borescope Fly aircraft at cruise power {
test reading below leakage inspection results. and repeat cylinder differential
limit. pressure test.

Cylinder differential pressure N/A Remove cylinder for repair.

test reading below leakage
limit after re-check.
Air discharge into exhaust Cylinder differential pressure Normal cylinder borescope Continue engine in service.
system test reading above leakage inspection results.
limit.

Cylinder differential pressure Normal cylinder borescope Fly aircraft at cruise power {
test reading below leakage inspection results. and repeat cylinder differential
limit. pressure test.

Cylinder differential pressure

test reading below leakage N/A
limit after re-check. Remove cylinder for repair
Air escaping at spark plug Cylinder differential pressure Dye check of area reveals Remove cylinder for
spot face test readings N/A cracks. replacement.
Air discharge at cylinder Cylinder differential pressure First cylinder head fin above Remove cylinder for
head to barrel juncture or test readings above leakage cylinder barrel wet with oil or replacement.
between barrel fins limit baked on oil residue. See also
latest revision of SB96-12 for
additional test to be performed.
{ Fly the aircraft at a cruise power setting between 65 and 75 percent power, as specified in the
aircraft Pilots Operating Handbook/Aircraft Flight Manual (POH/AFM), for a duration that
will allow the engine oil and cylinder head temperatures to stabilize, or at least 45 minutes.
Perform an additional differential compression test on the suspect cylinder(s).
| A sudden increase in oil consumption from the established or normal trend for the engine or an
oil consumption rate that exceeds 1/2 quart (liter) per hour during normal engine operation.
C. CYLINDER BORESCOPE INSPECTION
(a) Required Equipment:

In addition to the standard complement of tools required to perform maintenance and repairs on aircraft
engines the following tools and equipment are required to perform a cylinder borescope inspection.

1. Borescope.

• AUTOSCOPETM – Lenox Instrument Company. See Figure 5. Recommended by TCM.

Q. A. Technologies
PO Box 61085

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 Savannah, GA 31420
Phone: 912-330-0500
Fax: 912-330-0104
E-mail: sales@qatek.com
Web-site: qatek.com
Note: TCM customers receive a special discount when ordering from Q. A. Technologies.

FIGURE 5
(b) Performing the Inspection:
CAUTION
Take preventative measures to avoid burns when performing a borescope inspection on a hot engine.
1. If not already removed for differential pressure test, remove the upper spark plug from each cylinder.
2. Position piston at bottom dead center on the power stroke. The exhaust valve will be open with the
piston in this position.
3. Insert the borescope probe through the upper spark plug hole and inspect the internal surfaces of each
cylinder, including the exhaust valve and exhaust valve seat in accordance with Table 2.
4. After completing inspection steps 1,2 and 3; position piston at bottom dead center at the end of the
intake stroke.
5. Insert the borescope probe through the upper spark plug hole and inspect the intake valve and intake
valve seat in accordance with Table 2.
TABLE 2
Borescope Inspection Objectives And Corrective Actions
ITEM Objective If Abnormality Noted
Inspect:
1. Valve seat inserts for erosion, burning.
2. Sparkplug heli-coils for protrusion into combustion 1. Remove cylinder for repair
chamber. 2. Remove cylinder for repair
Combustion 3. Heavy carbon deposits/presence of excessive oil.
chamber. 3. Remove cylinder for repair.

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 Inspect for signs of leakage or damage, indicated by:
1. Localized discoloration on the valve face circumference. 1. Repair or replace cylinder.
See Figure 7 page 12
2. Minute cracks. 2. Repair or replace cylinder.
Exhaust valve face 3. Erosion (missing material). 3. Repair or replace cylinder.
Inspect for signs of leakage or damage, indicated by:
1. Localized discoloration on the valve face circumference. 1. Repair or replace cylinder.
Intake valve face. 2. Erosion (missing material) 2. Repair or replace cylinder.
Cylinder Bore. Inspect exposed surface of bore for:
1. Heavy scoring/piston rub. See Figure 10 on page 13.
2. Piston pin rub (wide ban pattern in horizontal plane at 3 1. Repair or replace cylinder.
o’clock and/or 9 o’clock position). 2. {
3. Upper portion of cylinder bore has no visible hone
pattern. See Figure 11 &12 on page 13 and 14. 3. Normal indication for in
service cylinders

4. Corrosion. See Figure 9, on page 12.

4. |
5. Excessive oil in cylinder/heavy deposits of carbon in
combustion chamber 5. Remove cylinder for repair
Inspect for:
Piston Head. 1. Piston crown for erosion, missing material 1. Remove cylinder for repair
2. Visible damage from foreign debris.
2. Remove cylinder for repair
Experience and expertise in borescope examination requires the aviation technician to perform borescope
inspection on a consistent basis. It is especially important that the technician perform borescope inspections
prior to removal of a cylinder for any reason so that they may validate by visual indications viewed through
the borescope, the actual conditions.
The following photographs are provided as a guide to the aviation technician when performing borescope
examinations. Teledyne Continental Motors welcomes inquiries and comments from the aviation
technician. We urge you to call your Regional Service Representative or Teledyne Continental Motors
Technical Support at (888) 826-5465.

{ Remove cylinder for repair or replacement. Perform complete inspection of connecting rod bushing
for correct installation and finishing. Refer to latest revision of TCM SB 00-3.
| Refer to the latest revision of TCM Service Information Directive (SID) 97-2. See Figure 9.
Normal Combustion Chamber. Exhaust
valve has reddish combustion deposit in
center with dark outer edge. Intake valve
has light brown combustion deposits.
Combustion chamber has light brown
deposits.

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 FIGURE 6 FIGURE 7

Phosphated cylinder bore. Note phosphate

New Phosphate coated cylinder bore with coating remaining in valleys of cylinder bore hone
revised cylinder bore hone pattern. Phosphate pattern. Light corrosion at top of cylinder bore,
coating provides increase corrosion protection above piston ring travel limit. Presence of light
during the initial hours of engine operation. corrosion in this area is normal.

FIGURE 8 FIGURE 9

Burned exhaust valve. Note edge of

valve face that has lost all
combustion residue and striations
moving toward center of valve.

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 FIGURE 10 CYLINDER BARREL SCORING / PISTON
RUB

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 FIGURE 11 TYPICAL IN SERVICE CYLINDER BARREL
UPPER RING TRAVEL AREA

FIGURE 12 TYPICAL IN SERVICE CYLINDER BARREL

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