TECH DOWNLOAD : Leakdown Test

By: APR | 03/31/2015 < Back to Blog Home

A leakdown test is a static type procedure that can assist in isolating a mechanical component failure.

STEP 1. With a warm engine, remove all four ignition coils and spark plugs.

STEP 2. Place a long, straight piece of light weight wire into the spark plug hole of the number 1 cylinder. Refrain from using heavy or sharp items as this may dent or scratch the top of the piston.

STEP 3. Using a socket and extension rotate the crankshaft clockwise until the number 1 piston is at top dead center (TDC)

STEP 4. Prior to installing your leakdown tester, verify that the gauge is reading zero and the hose you are about to install DOES NOT contain a one way schrader valve.

STEP 5. Install the hose into the number one cylinder spark plug hole and connect the gauge. Note, if the piston was not at perfect TDC, the crankshaft may rotate when pressurized. If this happens, releave the air pressure and reset the number 1 piston to TDC.

STEP 6. Read the gauge set. Compare the supply pressure on the left gauge with the amount of air escaping on the right gauge. The deveiation is the percentage of leakdown. The kit your gauge came with should provide a method for determining this amount. Record the data for each cylinder. Less than 3-5% leakdown is acceptable.

STEP 7. If leakage is present, probe the intake and exhaust runners with a stethoscope. Remove the coolant resevoir cap to check for air bubbles caused from a leaking headgasket and remove oil filler cap to listen for air leaking past the piston rings.

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