Valve noise (Audi A4 B6)

Valve noise that occurs when the engine is not warmed up is not a cause for concern. On the contrary, if noise is observed when the engine is warmed up to operating temperature, this almost always indicates a bearing failure. Most often, defects occur in the connecting rod plain bearings. Main bearing failure is much less common.

When a bearing fails, a major engine overhaul is usually necessary. However, if the connecting rod failure is recognized in a timely manner, then replacing the bearing shells is sufficient to eliminate the failure.

Signs of bearing failure

When parked, bring the engine speed to medium rpm, release the gas. Is there a slight knock when the rpm decreases? Do you also hear this slight knock when accelerating quickly?

If this is the case, it is better not to go any further. The malfunction may worsen, after which it will be impossible to eliminate it using simple methods.

A loud knock at high engine speeds, which becomes quieter or stops altogether when the accelerator pedal is released, indicates a serious bearing failure.

(The original article is available on the online resource: AudiManual)