What the camshaft bearings do
The camshaft bearings support the camshaft as it rotates, allowing it to spin freely under the pressure of the valve springs while maintaining precise clearances. They rely on a constant, clean supply of oil under pressure. When bearings wear — often as a result of oil starvation, degraded oil, or simply age and mileage — clearances increase and the camshaft can develop play.
How it differs from chain-related noise
- A deeper, more consistent knocking noise rather than a rattle confined to start-up
- Noise that tends to persist or worsen with engine speed, rather than settling once oil pressure builds
- Often accompanied by low oil pressure warnings
Why this needs prompt attention
Continued running with worn camshaft bearings risks the camshaft seizing or causing further internal damage, which significantly increases the scope and cost of repair. Because the symptoms can overlap with timing chain issues, a proper diagnostic — rather than an assumption — is essential to identify which is actually the cause before any work is booked.