BMW timing chain problems: which engines are affected and the warning signs

The BMW timing chain is one of the most important parts inside the engine. It connects the crankshaft to the camshafts and keeps the valves and pistons moving in perfect time. Unlike a timing belt, a chain has no fixed replacement interval and is designed to last the life of the engine.

In reality, a few BMW engines became known for timing chain and guide problems. In this guide we explain what the timing chain does, which engines are most affected, the warning signs to listen for, and how maintenance and early action can prevent expensive damage.

What the BMW timing chain does

In a four-stroke engine, the valves must open and close at exactly the right moment in relation to the pistons. The timing chain drives the camshafts from the crankshaft and keeps this relationship correct at every engine speed.

The chain runs over sprockets and is held in place by plastic guides and a hydraulic tensioner, which uses engine oil pressure to keep the chain tight. On engines with VANOS, the camshaft position can also be adjusted by the variable timing units, but the chain still provides the basic drive.

Most BMW engines use timing chains instead of rubber belts. A chain is stronger and does not need replacing at fixed intervals. But a chain can stretch over time, and the guides and tensioner can wear. If the chain jumps a tooth or breaks, the valves can hit the pistons, causing serious engine damage on most engines.

Why timing chains wear

A chain is made of many small links and pins. Over many thousands of kilometres, tiny amounts of wear in each pin add up and the chain becomes slightly longer. This is called chain stretch. The tensioner compensates for some stretch, but only up to a point.

Several factors speed up wear:

• Long oil change intervals and old, dirty oil.
• Low oil level, which reduces oil pressure to the tensioner.
• Many short trips and cold starts, when oil pressure takes a moment to build up.
• Weak guide materials or design details on specific engines.
• Incorrect oil that does not meet BMW approval.

Because the tensioner and VANOS units depend on oil, oil quality is one of the most important factors for a long timing chain life.

Engines known for timing chain problems

Most BMW engines have reliable timing chains, but a few became known for problems:

• N47 four-cylinder diesel. Produced from 2007, it has the timing chain at the back of the engine, next to the gearbox. Some engines suffered from chain wear and failure. Because of the location, the engine usually has to be removed to replace the chain, which makes the repair expensive.
• N20 four-cylinder petrol. Early versions of this turbo engine, used from around 2011, had problems with timing chain guides. BMW later introduced improved parts.
• N63 V8. Early versions of this twin-turbo V8 had several known issues, and timing chain wear was among the items addressed by later updates and service measures.
• M62 V8 (1990s). Older V8 engines sometimes suffered from worn plastic guides and tensioner rails.

Newer engines from the B-series family, such as the B47, B48 and B58, have improved timing chain designs and are generally considered more robust.

Warning signs of a BMW timing chain problem

The most typical sign of a worn BMW timing chain or guide is a noise from the engine:

• A rattle or whirring noise at cold start, lasting a few seconds until oil pressure builds up.
• A whining or grinding noise from the timing chain area that changes with engine speed.
• A rattle at idle on a warm engine in more advanced cases.

Other signs can include:

• Fault codes for camshaft position or correlation between crankshaft and camshaft.
• Rough running or reduced performance.
• The engine warning light or a drivetrain malfunction message.
• Plastic fragments found in the oil filter or oil pan during service.

On the N47 diesel, the noise usually comes from the rear of the engine, near the gearbox. Any new rattle should be checked by a specialist quickly, because a chain that jumps or breaks can destroy the engine.

How a specialist checks the timing chain

A specialist can check the condition of the timing chain in several ways. Listening with a mechanic's stethoscope helps to locate the noise. Diagnostic software can read the camshaft and crankshaft correlation values, which show if the chain has stretched.

On some engines, the tensioner can be inspected to see how far it has extended. When the valve cover is removed, the visible part of the chain and guides can also be checked for wear.

If the chain is stretched or the guides are worn, the usual repair is to replace the chain, guides, tensioner and often the sprockets as a complete set. On engines where the chain sits at the back, such as the N47, the labour cost is high because the engine or gearbox must be removed.

Acting early is much cheaper than repairing an engine after the chain has failed.

How to reduce the risk

You cannot change the design of your engine, but you can give the timing chain the best conditions:

• Change the oil regularly. Many enthusiasts choose shorter intervals than the maximum allowed by Condition Based Service.
• Use the correct BMW-approved oil. Our article on BMW M engine oil explains the approvals.
• Keep the oil level correct. Check it regularly and top up when needed.
• Let the oil warm up before using high engine speeds. Our guide on how to warm up a BMW M engine explains why.
• Listen at cold start. Notice any new rattle and act quickly.

When buying a used BMW with one of the engines mentioned above, ask whether the timing chain has already been replaced and check the service history for regular oil changes.

Buying a used BMW: what to ask

The BMW timing chain is a key topic when buying a used car with an N47, N20 or early N63 engine. Useful questions include:

• Has the timing chain, guide or tensioner been replaced? Is there an invoice?
• How often was the oil changed, and with which oil?
• Does the engine make any noise at cold start?

Ideally, listen to the engine yourself after it has been parked overnight. A healthy engine starts quietly. A rattle in the first seconds is a warning sign.

A pre-purchase inspection by a BMW specialist is always a good investment. Our checklist for buying a used BMW M car explains other points to check. With good maintenance and early action, a BMW timing chain can last for a very long time.

BMW timing chains at a glance

Item	Details
Function	Drives the camshafts from the crankshaft
Replacement interval	None; designed for engine life
Main wear	Chain stretch, worn guides and tensioner
Engines with known issues	N47 diesel, early N20, early N63, older M62
Typical sign	Rattle or whirring noise at cold start
Repair	Chain, guides, tensioner and sprockets as a set
Prevention	Regular oil changes, correct oil, correct oil level

Frequently asked questions

Do BMW timing chains need replacing?

There is no fixed interval. The chain is designed to last, but it should be replaced if it stretches or the guides wear.

Which BMW engines have timing chain problems?

The best-known examples are the N47 diesel, early N20 petrol engines and early N63 V8 engines. Newer B-series engines are generally more robust.

What does a bad timing chain sound like?

Usually a rattle or whirring noise for a few seconds after a cold start. In advanced cases the noise can also be heard at idle.

Can a timing chain break without warning?

It usually gives warning noises first, but not always clearly. That is why new rattles should be checked quickly.

Does oil quality affect the timing chain?

Yes. Clean, correct oil and the right oil level are essential, because the tensioner works with oil pressure.

Sources

• BMW service information – engine timing and maintenance
• BMW Group PressClub – engine technical descriptions