Cylinder Leakage Test

When a cylinder produces a low reading, the use of Rotunda Pressurization Kit 014-00705 or equivalent is helpful in pinpointing the exact cause.

The leakage detector is inserted in the spark plug hole and the piston is brought up to top dead center on the compression stroke and compressed air is admitted.

Once the combustion chamber is pressurized, a special gauge will read the percentage of leakage. Leakage exceeding 20 percent is considered excessive.

While the air pressure is retained in the cylinder, listen for the hiss of escaping air. A leak past the intake valve will be audible in the throttle body. A leak past the exhaust valve can be heard at the tail pipe. Leakage past the ring will be audible at the Positive Crankcase Ventilation (PCV) connection. If air is passing through a blown head gasket to an adjacent cylinder, the noise will be evident at the spark plug hole or the cylinder into which the air is leaking. Cracks in the cylinder block or head gasket leakage into the cooling system may be detected by a stream of bubbles in the radiator.