Warm the engine to operating temperature
Turn off the engine
Disable fuel and ignition systems
Remove all spark plugs
Bring cylinder 1 to top dead center on the compression stroke
Lock the crankshaft in place
Connect the leak down tester to a regulated air supply
Zero or calibrate the tester according to the manufacturer’s instructions
Thread the tester hose into the spark plug hole
Connect the tester to the cylinder
Apply compressed air to the cylinder
Read the leakage percentage on the gauge
Listen for air escaping from the intake, exhaust, oil filler, or cooling system
Record the leakage reading for the cylinder
Repeat for each cylinder, setting each one to top dead center on the compression stroke
Compare all readings to identify problem cylinders
Reinstall the spark plugs
Reconnect fuel and ignition systems
Start the engine if needed and verify operation