This procedure tests engine compression and cylinder sealing by pressurizing each cylinder with compressed air and measuring air loss, identifying worn piston rings, valves, or head gasket issues.

Warnings

Tools required

Parts

• Spark plug gaskets/washers (if reusing spark plugs) × 4 — Use OEM specification

Preparation

1. Warm engine to full operating temperature by running for 10-15 minutes
2. Park vehicle on level surface and engage parking brake
3. Turn ignition off and remove key
4. Allow engine to cool for 15-20 minutes to prevent burns while remaining warm for testing
5. Open hood and secure in raised position
6. Disconnect negative battery terminal to prevent accidental starting
7. Remove engine cover by pulling upward on cover to release clips
8. Label all ignition coil connectors with cylinder numbers (1-4, front to back)
9. Verify compressed air source is regulated to 90-100 PSI

Procedure

1. 1

   Remove ignition coils
   Disconnect electrical connectors from all four ignition coils by pressing release tabs. Remove the mounting bolt from each coil (10mm socket). Carefully pull each coil straight up and out of spark plug wells. Set coils aside in order.
   Torque spec

   Sensor Bolts10 Nm (8 lb-ft)
2. 2

   Remove all spark plugs
   Using spark plug socket and extension, remove all four spark plugs. Turn counterclockwise to loosen. Keep plugs in order (cylinders 1-4) for inspection. Inspect plug condition and note any abnormalities that may correlate with leak-down results.
   ⚠Spark plugs may be hot. Allow adequate cooling time before removal.
3. 3

   Rotate engine to TDC for cylinder 1
   Using breaker bar or ratchet on crankshaft pulley bolt (19mm), rotate engine clockwise (viewed from front) until cylinder 1 is at Top Dead Center (TDC) on compression stroke. Both intake and exhaust valves should be closed. Verify by checking that rocker arms for cylinder 1 are loose and can be moved slightly.
   ℹ️Ensure transmission is in Park (automatic) or neutral (manual) before rotating engine.
4. 4

   Install leak-down tester adapter
   Thread the leak-down tester adapter (matches spark plug thread size 14mm x 1.25) into cylinder 1 spark plug hole. Hand tighten securely, then snug with wrench. Do not over-tighten the adapter.
   ⚠Apply light coating of anti-seize to adapter threads to prevent seizing in aluminum head.
5. 5

   Test cylinder 1 for leakage
   Connect leak-down tester to adapter and compressed air source. Slowly introduce air pressure while ensuring piston does not rotate (it should be held at TDC by compression). Read gauge showing percentage of leakage. Record result. Acceptable leakage is typically 5-10%, marginal is 10-20%, and over 20% indicates significant wear. Listen at oil fill cap (rings), throttle body (intake valve), exhaust pipe (exhaust valve), and coolant reservoir (head gasket) to identify leak source.
   ⚠️If piston is not at TDC, air pressure will forcefully rotate engine. Ensure TDC position before applying air pressure.
6. 6

   Test cylinder 2
   Release air pressure and remove tester from cylinder 1. Rotate crankshaft 180 degrees clockwise to bring cylinder 2 to TDC compression stroke (approximately half rotation). Verify valves are closed. Install adapter into cylinder 2, connect tester, and perform leak-down test. Record percentage and identify leak source if applicable.
7. 7

   Test cylinder 3
   Release air pressure and remove tester from cylinder 2. Rotate crankshaft another 180 degrees clockwise to bring cylinder 3 to TDC compression stroke. Verify valves are closed. Install adapter into cylinder 3, connect tester, and perform leak-down test. Record percentage and identify leak source if applicable.
8. 8

   Test cylinder 4
   Release air pressure and remove tester from cylinder 3. Rotate crankshaft another 180 degrees clockwise to bring cylinder 4 to TDC compression stroke. Verify valves are closed. Install adapter into cylinder 4, connect tester, and perform leak-down test. Record percentage and identify leak source if applicable.
9. 9

   Analyze test results
   Compare all four cylinder readings. Variance between cylinders should be less than 5%. High leakage (over 20%) indicates: air from oil cap = worn rings/cylinder, air from throttle body = intake valve leaking, air from exhaust = exhaust valve leaking, air from coolant reservoir = head gasket failure. Consistent high leakage across all cylinders may indicate valve timing issue or general wear.
10. 10

    Reinstall spark plugs
    Inspect spark plug threads and clean if necessary. Install new gaskets/washers on spark plugs if reusing. Thread each spark plug by hand into correct cylinder to prevent cross-threading. Tighten spark plugs to specification using torque wrench. For new plugs: 18-22 Nm (13-16 lb-ft). For reused plugs with new washers: 15-18 Nm (11-13 lb-ft).
    ⚠Do not over-torque spark plugs in aluminum cylinder head. Cross-threading will cause expensive head damage.
11. 11

    Reinstall ignition coils
    Insert each ignition coil into correct spark plug well, ensuring coil seats fully on spark plug. Install mounting bolt and torque to specification. Reconnect electrical connector to each coil, ensuring positive click engagement.
    Torque spec

    Sensor Bolts10 Nm (8 lb-ft)
12. 12

    Final assembly
    Reinstall engine cover by aligning clips and pressing down firmly until all clips engage. Reconnect negative battery terminal. Clear any diagnostic trouble codes that may have been set during testing.

Reassembly

1. Ensure all ignition coil connectors are fully seated and locked
2. Verify engine cover is properly clipped in place
3. Double-check that all tools and test equipment are removed from engine bay

Verification

• Start engine and verify smooth idle with no misfires
• Check for any unusual noises or vibrations that were not present before testing
• Verify leak-down percentages were recorded for all cylinders and results are documented
• Acceptable results: 5-10% leakage per cylinder with less than 5% variance between cylinders
• If any cylinder showed over 20% leakage, further diagnosis and repair is required

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