In an engine, a tappet is responsible for transferring the motion of a camshaft to the pushrods and valves in an overhead valve (OHV) engine. In just overhead valve mechanism system has tappet. If the tappet noise, the tik-tik sound comes from the engine compartment. In this article, I will discuss the various types of tappet noise causes.
Tappet and valve give clicking noise. Its frequency is lower than that of any other noise of the engine because the valves are controlled by the camshaft, whose speed is half that of the engine. If only one or two valves are noisy, the sound will be intermittent, otherwise, it may be continuous.
There are two main types of tappets: hydraulic and solid. Hydraulic tappets use oil pressure to maintain proper clearance between the tappet and the camshaft, while solid tappets rely on a specific amount of clearance set manually during engine assembly or maintenance. The possible cause of valve and tappet noises are as follows-
Excessive tappet clearance-
Tappet clearance means the clearance between the tappet and the valve tip. Excessive tappet clearance can cause tappet noise, which is called “Valve Lash”. It will result in the valve not opening and closing at the correct time.
When the camshaft lobe rotates back around, the valve may not open as quickly as it should, causing a tapping or clicking noise as it slams against the tappet. The clearance between the valve and the tappet will cause the engine oil to drain into the engine combustion chamber, causing engine damage.
Worn thread of set screws-
Worn threads on set screws can cause tappet noise in an engine. It allows the tappet to move and make contact with the valve stem or rocker arm, creating a tapping or clicking noise.
When the set screw tappet clearance increases, the tappet may move more, causing it to contact the valve stem or rocker arm. This can result in a tapping or clicking noise that is often referred to as “tappet noise” or “valve clatter”. The worn set screw threads can cause the tappet clearance to change over time. This can also cause other problems such as reduced engine performance or valve damage.
Broke valve springs-
The valve springs are the reasons for the valve to return to its own position. If the valve spring breaks, it will cause a ticking or clicking noise.
When a valve spring is broken, It will not open and close at the right time. Broken valve springs can cause other issues such as reduced engine performance, engine misfires, and even engine damage. When a valve spring is broken, the valve may not be able to close properly, which can lead to a loss of compression and reduced engine power.
Excessive valve steam-to-guide bore clearance-
Excessive clearance in between the valve stem and guide bore will cause damage to the valve and also create clicking noise. The valve guide is a cylindrical component that provides support and guidance to the valve stem as it moves up and down in the engine. Excessive valve set,-to-guide bore clearance, can also damage the engine’s internal parts.
When the clearance is too high, then the valve stem will not get proper support. It will start to move or wobble inside the bore clearance. This can cause the tappet to make contact with the valve stem or rocker arm at the wrong time.
Excessive push-rod-to guide clearance-
The camshaft lobs push the push rod, then the push rod pushes the tappet, resulting opening of the valves. Excessive clearance between the push rod and the valve guide will also cause the tappet noise.
When the clearance increases between the push rod and guide it will unable to open the valve properly. The valves are open in proper sequence, if there is any lag in the system then the pre-ignition or retarded ignition will happen. The clearance will make the clicking or sticking sound.
A tappet is responsible for the opening of the valves at the correct time. If there is any problem in the tappet it will cause serious damage. Tappet noise is a common problem in the overhead valve mechanism system. The system is a little bit complicated with the extra fitment of the push rod. The clicking and ticking sound are very annoying while driving a car or bike. So maintenance and checkup is a good process to save the engine and relief the noise.