Engine Noise Diagnosis (Valve Train)

A light tapping at one-half engine speed, or any varying frequency, can indicate a valve train problem. These tapping noises increase with the engine speed. Warm up the engine before attempting to judge the valve train noise. This will bring all of the engine components to a normal state of expansion. Run the engine at various speeds and listen for engine noise with the hood closed.

Caution: The following procedure is not recommended on engines with stainless steel exhaust manifolds because 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 rocker arm covers and use a stethoscope to determine which valve train components are causing the noise. The causes of the valve noise include the following conditions:
^ Broken or weak valve springs
^ Sticking or warped valves
^ Bent push rods
^ 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
^ Worn push rods
^ Worn valve rocker arms
^ Broken valve rocker arm bolt
^ Loose or worn valve rocker arm attachments
^ Missing or improperly positioned lifter guides (roller lifter engines)






Momentary Noise on Engine Start-up






Intermittent Noise on Idle Only






Noise At Idle






Noise Vehicle At High Speeds






Noise at Idle, Louder at High Engine Speed






Noise at any Engine Speed