Cylinder Leakage Test

The combustion pressure leakage test provides an accurate means for determining engine condition.

Cylinder leakage testing will detect:

Check the coolant level and fill as required. DO NOT install the radiator cap.
Start and operate the engine until it attains normal operating temperature, then turn the engine OFF.
Remove the spark plugs.
Remove the oil filler cap.
Remove the air cleaner hose.
Calibrate the tester according to the manufacturer's instructions. The shop air source for testing should maintain a regulated air pressure at 552 kPa (80 psi).
Perform the test procedures on each cylinder according to the tester's manufacturer instructions. Set the piston of the cylinder to be tested at Top Dead Center (TDC) on the compression stroke.
As each cylinder is pressurized, listen for the air escaping through the throttle body, tailpipe and oil filler cap opening. Check for bubbles in the radiator coolant.

All gauge pressure indications should be equal, with no more than 25% leakage.

If leakage is greater then 25%, refer to CYLINDER LEAKAGE DIAGNOSIS CHART below.

CYLINDER LEAKAGE DIAGNOSIS CHART

CONDITION	POSSIBLE CAUSE	CORRECTION
AIR ESCAPES THROUGH THROTTLE BODY	Intake valve bent, burnt, or not seated properly	Inspect valve and valve seat. Reface or replace, as necessary. Inspect valve springs. Replace as necessary.
AIR ESCAPES THROUGH TAILPIPE	Exhaust valve bent, burnt, or not seated properly	Inspect valve and valve seat. Reface or replace, as necessary. Inspect valve springs. Replace as necessary.
AIR ESCAPES THROUGH RADIATOR	Head gasket leaking or cracked cylinder head or block	Remove cylinder head and inspect. Replace inoperative part.
MORE THAN 50% LEAKAGE FROM ADJACENT CYLINDERS	Head gasket leaking or crack in cylinder head or block between adjacent cylinders	Remove cylinder head and inspect. Replace gasket, head, or block as necessary.
MORE THAN 25% LEAKAGE AND AIR ESCAPES THROUGH OIL FILLER CAP OPENING ONLY	Stuck or broken piston rings; cracked piston; worn rings and/or cylinder wall	Inspect for broken rings or piston. Measure ring gap and cylinder diameter, taper and out-of-round. Replace inoperative part as necessary.