Engine Leakdown Test

Hearing Problems
Beyond getting an overall picture of engine condition, the leakdown test is an excellent way to pinpoint where engine problems are before tearing down the engine. Listening for where the air is escaping by ear can isolate the problem. Intake Valve: Air whistling out of the intake, carburetor, or throttle body indicates leak at the intake valve. Exhaust Valve: Air heard hissing out of the tailpipe, turbocharger, or exhaust manifold means an exhaust valve leak. Piston Rings: Whistling or hissing out of the PCV valve, oil filler cap hole, or dipstick tube means the air is pushing past the rings. Suspect ring or cylinder wall wear. Head Gasket: Air bubbles in engine coolant seen at the radiator filler cap could mean air escaping into the coolant past the head gasket. Cracked Cylinder Head: Bubbles in coolant or coolant being pushed up out of the radiator neck can also indicate cracks in the cylinder head or cylinder walls.

Tools & Supplies
You will need a compressed air source, a leakdown gauge kit, spark plug socket, basic hand tools, vehicle service manual, and a notepad to record results.

About the Author
Mike Bumbeck spends a great deal of his time in Los Angeles photographing, repairing and writing about cars and their odd effect on those obsessed with their powers.