What this test proves

Identify cylinder leakage paths while the piston is stationary at the specified position.

Tools

  • Regulated cylinder leakage tester and correct adapter
  • Compressed-air supply within tester rating
  • Approved crankshaft holding method

Preparation and precautions

  • Position the piston at compression TDC with both valves closed per OEM instructions.
  • Air pressure can rotate the engine suddenly. Secure the crankshaft by the approved method and keep hands/tools clear; Park alone is not a crankshaft lock.

Connections

  • Connect the adapter to the cylinder. Calibrate the tester as its manual directs before admitting air to the engine.

Equipment settings

  • Use the tester’s specified regulated inlet pressure and calibration procedure. Different tester restrictions can give different percentage readings.

Test sequence

  1. Confirm piston position and secure rotation.
  2. Admit air gradually and record leakage.
  3. Listen at intake, exhaust and crankcase; check cooling-system indications only using a safe approved method.
  4. Release pressure before moving the crankshaft or disconnecting.
  5. Repeat under consistent conditions.

Expected signal / readings

Leakage should meet the engine and tester procedure. Some ring leakage is normal; location and cylinder-to-cylinder comparison matter.

Interpreting results

  • Intake or exhaust leakage can implicate the corresponding valve path.
  • Crankcase leakage can involve rings/cylinder sealing. Cooling-system bubbles need confirmation and may involve head, gasket or block faults.

Common mistakes

  • Testing on exhaust TDC
  • Letting the engine rotate under air pressure
  • Comparing percentages from differently calibrated testers