Rattle from the back of the engine at warm idle
- Make and model
- BMW 320d (E90)
- Year
- 2009
- Engine
- 2.0d (N47)
- Fuel
- Diesel
- Mileage
- 189,000 km
Customer complaint
A rattling, slightly whining noise from the gearbox end of the engine, loudest at idle when warm. It gets louder when the clutch is let out at a standstill. No warning lights.
Fault codes
No fault codes stored.
Measurements and live data
| Parameter / measurement | Measured | Expected |
|---|---|---|
| Fault memory | No faults stored | — |
| Engine oil level and condition | At minimum, very dark | between min and max |
Tests performed
- Stethoscope at the bell housing, warm idleRhythmic rattle from the rear of the engine, rising with rpm
- Recording compared with a known good N47Clearly louder, rattling instead of a faint whine
- Gearbox removed, rear timing cover offLower chain guide rail cracked, tensioner extended close to its limit
Solution
Root cause
Timing chain stretched with a cracked guide rail at the rear of the engine.
Repair
Engine removed; replaced the upper and lower timing chains, guide rails, tensioner and sprockets with the latest parts, plus a new crank bolt and seals. Oil and filter changed and the service interval set to 15,000 km.
Parts
Timing chain kit (chains, guides, tensioner, sprockets), seals, oil and filter
Labour time
12 h
Lesson learned
No fault code does not mean no problem: on the N47 the chain gives a noise warning long before it breaks.
Training case: the usual fix for this fault, not a confirmed repair on a specific car.
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