Valve Mechanism or Valve Train Noise

NOTE: A light tapping at one-half engine speed, or any varying frequency, can indicate a valve train problem. These tapping noises increase with engine speed. Warm up the engine before attempting to judge the valve train noise. By doing this you will bring all engine components to a normal state of expansion. While sitting in the driver's seat run the engine at various speeds and listen for engine noise with the hood closed. After a major engine repair or long periods of non-use, "Lifter Clatter" at initial start-up is normal. This should go away after 10-15 minutes of operating the engine at 1500 RPM. Operating the engine in this manner will purge all air out of the lifters.

WARNING: Do not remove the camshaft covers to diagnose valve train noises because exhaust manifold temperature will exceed the flash point of the oil causing a fire with possible personal injury.

If the valve mechanism is abnormally noisy, remove the valve covers and use a stethoscope in order to determine which valves or valve train parts are causing the noise. The causes of the valve mechanism noise include the following conditions:
^ Broken or weak valve springs
^ Sticking or warped valves
^ Dirty, stuck or worn valve lifters
^ Damaged or improperly machined camshaft lobes
^ Insufficient or poor oil supply to the valve train (low oil pressure)
^ Excessive valve stem to guide clearance
^ Worn valve guides