NOISY, BUT NOT ALWAYS DEFECTIVE VALVE LIFTERS
Hydraulic valve lifters are probably the most precision machined part inside any engine. It does not take much to cause one to operate incorrectly. In this case we are not referring to lifter failure due to metal to metal contact with the camshaft. In this case we’re talking about lifter noise and or a lifter that does not hold oil pressure and is unable to carry the pushrod properly through the full rotation around the cam lobe. – Noise from the lifter or valve train can come from something as simple as low oil level in the engine. Momentary lifter noise when an engine is started up is normal operation if the noise goes away in a few seconds. Oil drains from some of the lifters while the engine is not running. If the noise persists, oil level may be low in the engine allowing the oil pump to pump air into the oil galleys and into the lifters. An overfilled crankcase can also cause noise. The crankshaft counterweights can churn the oil into foam. When foam is pumped into a lifter it will be noisy. A damaged oil pan, or a loose or cocked pickup screen can also cause an oil pump to pump air to the lifters. Noisy operation at higher engine speed and little or no noise at low speed can be a sigh of air in a lifter. – A lifter that is noisy at idle to 1500 rpm may be caused by worn valvetrain. Check for worn or scuffed valve tip or rocker arm face, excessive valve stem to guide clearance, excessive valve seat or valve face runout, or a valve spring that is out of square. A valve spring damper clicking on a rotator can cause a similar noise. Worn pushrod tips or rocker ball seats can cause a continuous noise no matter what the rpm. This is especially common on roller lifter engines where the pushrod never spins, since the lifters are not rotating. – An intermittent noise that goes away with increased engine speed is usually caused by dirt. This may be due to poor maintenance or from a newly rebuilt engine that was not cleaned properly before reassembly. – There can be such a thing as a defective lifter, but there are several conditions that can lead to lifter noise and these should be checked before we just throw another set of lifters at any noise problem.
Engine Pro Tech Committee
with thanks to Federal Mogul Corp.
April, 2015
