What is the first sign of a BMW N47 timing chain problem?

A brief metallic rattle from the back of the engine on cold start, lasting one to ten seconds before it quietens down as oil pressure builds.

How much does it cost to fix an N47 timing chain?

Around £1,500–£2,500 at a specialist garage, £3,000+ at a main dealer, or £4,000–£6,000 for a replacement engine if the chain has already snapped.

Which BMW models are affected by the N47 timing chain fault?

4-cylinder N47 diesels built roughly 2007–2010/early 2011, including the 318d/320d, 520d, 120d/123d, and X1/X3.

Are later N47 engines safe?

Engines from around 2012 onwards had revised timing chain guides and are far less prone to failure.

BMW N47 Timing Chain Problems: What Every 320d/520d Buyer Must Check

If you’re looking at a used BMW 320d or 520d from around 2007–2010, you’ve probably heard whispers about the N47 timing chain. The good news? It’s a known issue with clear symptoms. The bad news? If it fails, the repair bill can be eye-watering. Let’s get into why this happens, what to listen for, and how to protect yourself when buying.

Why the N47 timing chain fails

The N47 is a 2.0-litre turbodiesel that BMW used across its range from 2007 onwards. It’s a clever, frugal engine that delivers good performance and great economy – which is why so many people still want one today. But the timing chain is its Achilles heel.

In most engines, you’ll find the timing chain or belt neat and accessible at the front. BMW decided to put the N47’s chain at the back of the engine, tight against the bulkhead. That means when something goes wrong, you can’t just pop the bonnet and swap it. The engine might have to come out completely.

The chain itself, along with its guides and tensioner, is known to wear prematurely on earlier N47 units. The plastic guides become brittle and break, allowing the chain to stretch and slap. In a worst-case scenario, the chain can jump or snap, causing valves to meet pistons – and that’s an engine replacement rather than a repair.

Which BMWs are affected?

The issue predominantly affects 4-cylinder N47 engines built from 2007 through to around 2010 or early 2011. The cars you need to be careful with include:

318d / 320d (E90, E91, E92, E93)
520d (E60, E61 and early F10/F11)
120d / 123d (E81, E82, E87)
X1, X3 and other N47-powered models

Later N47 engines (from around 2012) had revised timing chain guides and are far less prone to failure, but on a 2007–2010 example, it’s still a lottery.

The classic symptoms of N47 timing chain trouble

If you know what to listen for, the N47 timing chain issue is normally detectable before it becomes catastrophic. Keep an eye (and ear) out for:

A rattle on cold start – This is the classic one. On your first startup after the car has sat overnight, you’ll hear a brief metallic rattle from the back of the engine. It might only last a second or two – or up to ten seconds on a really worn chain.
Persistent rattling when idling – If the chain has stretched further, you may hear a constant rhythmic rattle, which often gets worse as the engine warms up.
Engine management light – If the chain has jumped, you’ll see the EML on the dashboard, often with codes relating to crank/cam synchronisation.
Rough running or misfiring – This could mean the chain has already skipped a tooth. The car may feel down on power and idle unevenly.
Whining or grinding in extreme cases – As guides disintegrate, pieces can get caught in the chain, making a harsher noise.

Not all failing chains make a racket, but a cold-start rattle is the number one warning sign. The trick is to test the car from cold – a normal test drive after the engine is warm might hide it completely.

How to check for N47 timing chain problems before you buy

Armed with a little knowledge, you can dramatically reduce your risk of inheriting a nightmare. Here’s a straightforward pre-purchase checklist.

1. Listen to a cold start

Ask the seller (or the dealership) to leave the car overnight – or at least for several hours – so it’s fully cold. Then start it and walk around to the front offside. Better yet, open the bonnet and stand near the windscreen base. If you hear a brief rattle, walk away or budget for the repair.

If you can’t arrange a cold start, see if the car has been recently driven. A hot start won’t reveal the issue.

2. Look for a full service history

Oil changes are critical to N47 chain life. The chain runs through engine oil, and contamination can accelerate wear. Look for evidence of the correct 5W/0W-30 or BDE spec oil at intervals no longer than 12,000 miles or 12 months. Regular independent servicing with receipts is fine – just make sure it’s there.

3. Ask about timing chain replacement

By now, many high-mileage N47s have already had this repair done. If you see an invoice for timing chain, guides, tensioner, or all three, that’s a huge plus. A completed job by a reputable specialist, ideally using the later updated guides, means the nightmare has already been sorted.

4. Check the engine bay for tell-tale signs

If the chain has been replaced, you might see fresh gasket sealant around the engine’s rear oil seal, or new bolt heads under the scuttle panel. You can also run the VIN through BMW or ask the seller directly when the work was carried out.

5. Get an independent inspection

If you’re not mechanical, pay a local BMW specialist to do a pre-purchase inspection. They have diagnostic tools and can spot issues you’d never see with a torch and a screwdriver.

How much does N47 timing chain replacement cost?

The repair itself is labour-intensive because of the chain’s location. Cutting corners is risky, so use someone who knows N47s well.

Specialist garage: Around £1,500–£2,500 for parts and labour, depending on the car and whether they drop the gearbox or pull the engine. This usually includes the chain, both guides, tensioner, and water pump while they’re in there.
Main dealer: £3,000+ is not unusual, partly due to parts markup and overheads.
DIY with engine out? You’d need to not be scared of a weekend job, but for reference, the parts kit alone is £300–£500.

If the chain has actually snapped, you’re looking at £4,000–£6,000 for a replacement engine fitted. That’s more than many of these cars are worth.

So, should you buy an N47-powered BMW?

This is the real trade-off. The N47 is otherwise a reliable, efficient engine. It offers excellent real-world fuel economy, plenty of torque, and a refined driving experience that makes BMWs great to cover long distances in.

If you find a 2007–2010 example with documented timing chain replacement, buy with confidence. If it’s never been done, use that as a bargaining chip. You could ask the seller to knock £1,500–£2,000 off the price to account for the potential work, then either budget for the repair now or play the odds on a lower-mileage car that may still be okay.

Better yet, look for a car built after 2012 or consider a petrol model if you’re not set on diesel. But if your heart is set on an early N47, just go in with open eyes.

One more thing to check

While you’re at it, ask about other common N47 issues like swirl flaps, EGR valves and the high-pressure fuel pump. A car with a faddy history can still surprise you, and it’s worth tallying up the overall condition before you commit.

The bottom line

The N47 timing chain issue isn’t an automatic deal-breaker – it’s a known, checkable fault. Spend time listening to cold starts, dig into the history, and don’t be afraid to ask awkward questions. If you do that, you could still bag a great car at a sensible price.

When you’re ready to make that change, UpCars.uk is a good place to look. Cars there are checked over properly before being listed, so you’ll have a clearer idea whether that N47 has had its chain done – or whether it’s a ticking time bomb. Happy hunting, and may your cold starts be quiet ones.