What are the symptoms of noisy engine tappets?

A ticking, tapping or clacking from the top of the engine is usually indicative of a potential issue with your engine’s tappets. At first it can seem insignificant in volume, but gradually over time the ‘rattling’ will get louder and indicate an imminent major mechanical issue.

If you’ve recently acquired a classic Mercedes online or from a classic car trader, listen out for these noises that tend to emerge from just one side of the engine. This is usually on the driver’s side for UK cars or passenger side for European and US SLs; sometimes you will hear these noises on both sides.

This tappet (lifter) noise can be very annoying and spoil the performance of an otherwise healthy V8 engine, making it sound worn, tired and on the eve of destruction.

What is an engine tappet?

An engine tappet, otherwise known as lifter or cam follower, is a small cylindrical mechanism attached to the end of a pushrod in overhead valve engines, or the rocker arm in overhead cam engines. A tappet is responsible for helping command the movement of the engine valves by limiting the gap between the camshaft and the valves; helping with the internal combustion process. Tappets are therefore essential to the timely mixture of air and fuel; and thus combustion.

Vehicles affected

Any SL with a V8 engine

Diagnosis

Worn hydraulic tappets/rocker arms which, in the worst case, will have affected the camshaft(s). This is due to infrequent or missed oil and filter changes or the use of an incorrect grade of engine oil, causing oil starvation to the top of the engine or sludging of the cylinder head oil ways. There are steps to be taken to solve this issue but first you must ensure you have determined it is an issue with tappets, rather than the rocker arm, camshaft, valves or all of four.

How to cure noisy engine tappets

Treatment of the problem depends on the severity of each case.
1. Firstly, an oil and filter change with the correct grade of oil can clear the oil ways and restore the compression to the hydraulic tappets if they are not worn.
2. Identify and replace any offending hydraulic tappet(s).
3. If the engine is ticking then replacing all 16 tappets (lifters) and rockers arms will rectify the situation.

In worst case scenarios, we would replace the camshaft(s) as well as all of the tappets and rocker arms. In addition and for extra peace of mind, we would recommend an oil and filter change.

Click here to view our R107 Hydraulic Tappets

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