Deep metallic engine knock in the 2.2 HDi engine: causes

1. • Medium severityFrequency: RareClutchDual-mass flywheel wear, less frequent than on other HDi enginesKnocking or metallic noise that changes with revs.

   Source for the symptom^[1]

• Play in the big-end or main bearings (rod knock)^[2][3]Common
• Lack of lubrication: low or degraded oil or insufficient pressure^[3][4]Common
• Stretched timing chain or tensioner without pressure^[2][3][5]Possible
• Hydraulic tappets and valves with play^[2][3]Possible
• Worn pistons and rings^[3]Uncommon
• Normal diesel engine noise^[3]Possible

What to check first

1. Stop the engine as soon as it is safe and check the oil level with the dipstick on level ground and with the engine cold or stopped for a few minutes; it is the first step recommended by Todoaditivos and RACE.^[2][4]
2. Look at the oil pressure warning light (red): if it is on along with the knocking, don't start the engine again and call assistance.^[2][4]
3. Note when it makes the noise: only when cold and for a few seconds (probably tappets or tensioner), or with the engine warm and growing with load and revs (much more serious).^[2][3]
4. Look for oil leaks on the ground or blue smoke, signs that the engine is losing or burning oil, according to RACE.^[4]

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