If a leak-down test shows leakage mainly through the intake valve path, what does that indicate?

If a leak-down test shows leakage mainly through the intake valve path, what does that indicate?

• A. Intake valve seating issue.
• B. Head gasket failure.
• C. Piston ring wear.
• D. Exhaust valve seating issue.

Answer: (A)

Leak-down testing identifies where air escapes when the cylinder is pressurized with the valves closed, showing which sealing surface isn’t doing its job. If most of the leakage is found along the path into the intake side, the intake valve isn’t sealing properly against its seat. That means the valve face or the valve seat isn’t making a true seal, which can be caused by carbon buildup, a worn or damaged valve face, a recessed or damaged seat, or a valve that isn’t seated correctly. The air escapes into the intake manifold area when the valve should be fully closed, pointing to an intake valve seating issue.

Leak-down testing identifies where air escapes when the cylinder is pressurized with the valves closed, showing which sealing surface isn’t doing its job. If most of the leakage is found along the path into the intake side, the intake valve isn’t sealing properly against its seat. That means the valve face or the valve seat isn’t making a true seal, which can be caused by carbon buildup, a worn or damaged valve face, a recessed or damaged seat, or a valve that isn’t seated correctly. The air escapes into the intake manifold area when the valve should be fully closed, pointing to an intake valve seating issue.