Why tappet noise come in engine?

Tappet noise in an engine is primarily caused by excessive clearance between the tappets (also known as valve lifters) and the camshaft lobes or the valve stems. This clearance is necessary to allow for thermal expansion and to prevent the valves from sticking, but if it becomes too large, it can cause the tappets to make a ticking or clattering sound as they move.

Several factors can contribute to tappet noise, including:

1. Worn Tappets: Over time, the tappets and camshaft lobes can wear, leading to increased clearance and noise.

2. Incorrect Valve Adjustment: If the valve lash (clearance) is set too loose, it can cause tappet noise.

3. Low Oil Pressure: Insufficient oil pressure can cause the hydraulic tappets to lose their ability to maintain proper clearance, resulting in noise.

4. Faulty Hydraulic Tappets: Hydraulic tappets can malfunction or become clogged, causing them to not function properly and leading to noise.

5. Worn Camshaft Lobes: Excessive wear on the camshaft lobes can create uneven surfaces that cause the tappets to make noise as they ride over them.

6. High Engine Temperatures: Extreme engine temperatures can cause the metal components to expand excessively, resulting in increased tappet clearance and noise.

To address tappet noise, it's important to identify the underlying cause. Depending on the specific issue, solutions may include adjusting the valve lash, replacing worn tappets or camshaft lobes, addressing low oil pressure, or servicing or replacing faulty hydraulic tappets. It's recommended to consult with a qualified mechanic or refer to the vehicle's service manual for specific instructions and recommendations for your particular engine.