No car owner wants to hear the engine start to emit unusual sounds. Not only annoying to the owner, these noises can also indicate other issues plaguing the car. Educate yourself about the various causes of engine noise, and take prompt corrective steps upon identifying the problem.
Lifters are the devices that sit on the camshaft lobe and play an instrumental role in opening the intake and exhaust valves. A substandard lifter that has become worn out, dirty or leaky can be a major cause of tapping noises. Low oil pressure or a plugged oil galley will result in a restricted flow of oil to a lifter, which can also adversely affect its ability to work properly. This collapsed lifter consequently causes excessive noise.
The gap between the camshaft and the valve in an internal combustion engine is known as a "valve lash." An excessive space between the rocker arms and the stems of the valves can lead to a noisy valve and accelerated damage to both parts. On older engines, the valve lash requires periodic adjustment with a feeler gauge.
A knocking engine sound usually indicates a major problem affecting the engine. Chief causes include rod bearings that have become worn out or loosened enough to make a dull noise. This wear indicates that the rod bearing requires immediate replacement prior to the bearings failing, which can necessitate repair or replacement of the entire engine. Other reasons for knocking include low oil pressure, low viscosity of oil, dirt, worn-out cylinders or loose bolts. All of these issues can result in the need for a complete engine overhaul.
