INA: Air bleeding of hydraulic valve lash adjustment components

Recommendations to eliminate valve train noise

Valve train noise can occur under certain operating conditions (multiple start-ups, cold start, engine initial assembly). Observe the following instructions to ensure rapid bleeding of the high-pressure chamber and reservoir of the hydraulic element:

➜ Keep the engine running at a constant speed of approx. 2,500 rpm or at variable speeds in the 2,000 to 3,000 rpm range for at least 4 minutes.

➜ Then keep the engine idling for approx. 30 seconds.

➜ The system is bled if no more noise is audible. If valve train noise persists, repeat steps 1 and 2.

In 90 % of cases, valve train noise is eliminated after the first air bleeding cycle. In very few cases, it may be necessary to repeat the procedure up to 5 or 6 times. If valve train noise is still perceptible after the fifth bleeding cycle, it is recommend to replace the relevant parts and perform additional tests.

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Published on: February 7, 2021

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