Rear timing chain stretch and breakage on the BMW N47

• A metallic rattle or ticking in the first few seconds after a cold start, especially noticeable at around 1,000-1,500 rpm, which usually fades as the engine warms up.^[2][5][8]Chain noise: other faults that cause it · Garage soon
• Vibrations or a less smooth idle than normal as the chain loses tension.^[8]Vibrations: other faults that cause it · Monitor
• Engine warning light on when the ECU detects a timing mismatch between the crankshaft and the camshafts.^[13]Engine warning light: other faults that cause it · Garage soon
• In the worst case, the chain breaks without warning and the engine stops dead, even while driving.^[7][9]Engine stalls: other faults that cause it · As soon as possible
• If the breakage has damaged pistons or valves, a serious internal knocking appears, which makes it inadvisable to keep driving.^[14]Engine knock: other faults that cause it · As soon as possible

It affects, to varying degrees, the entire N47D20 production and its MINI derivatives N47C16/N47C20. Units built between 2007 and 2009, and in particular those covered by BMW's technical campaign between February 2007 and June 2008, account for the most serious cases, although there are documented failures on later engines, even up to 2015.^{[1][3][10][11]}

Prices in Spain, including VAT. A workshop hour costs on average €38–66 at independent garages and €77–134 at dealerships in Spain, depending on the region and the brand. How we calculate costs

• Start the car from cold yourself and listen closely to the first few seconds: a metallic rattle at around 1,000-1,500 rpm that disappears as the engine warms up is the most cited warning sign.^[2][5][8]
• Ask for the service history and explicitly ask whether the timing chain has been checked or replaced, with an invoice; on units registered before 2011 the documented risk is higher.^[1][9]
• If possible, ask a BMW/MINI specialist workshop to measure the chain stretch with the specific tools before you close the purchase.^[15]
• Be wary of cars with very long oil change intervals: degraded oil speeds up wear of the tensioner and guides.^[9]

• Reinforced timing chain kit (chain, tensioner, guides and sprockets)^[6][16]

  Replaces the original components, often with a kit with reinforced guides and tensioner, to reduce the risk of the fault recurring.

  Buy part at Autodoc (affiliate link, opens in a new tab)

• Rear crankshaft seal^[6]

  Routinely replaced when the engine is removed to reach the chain, as it sits right behind the timing sprockets.

  Buy part at Autodoc (affiliate link, opens in a new tab)

• Complete N47D20 engine (rebuilt or from a breaker)^[8]

  An alternative when the chain has broken and wrecked pistons, valves or the cylinder head; in those cases replacing the whole engine can work out cheaper than repairing it part by part.

  Buy part at Autodoc (affiliate link, opens in a new tab)

• Shorten the oil and filter change interval to below what the on-board computer indicates, especially if the car does a lot of short urban journeys and cold starts.^[2][9]
• Consider preventive replacement of the chain, tensioner and guides if the car has passed 100,000-120,000 km with no record of it having been done, instead of waiting for it to fail.^[8][17]
• If you notice the characteristic rattle when cold, do not wait: get the car checked straight away, because on an interference engine a breakage can destroy it.^[14]

• Technical campaignBMW · 2008

  Technical campaign to replace the tensioner and, if necessary, the timing chain

  According to the Irish and British press, BMW carried out a technical campaign to replace the timing chain tensioner, and the chain if necessary, on N47 units built between February 2007 and June 2008. Outside that period, and once the warranty has ended, BMW has handled failures case by case through goodwill contributions, without acknowledging a widespread manufacturing defect or calling a formal recall in the United Kingdom, Ireland or the rest of the European Union.^[10][11]

• Legal actionConsumidores / tribunales españoles · 2018

  Owner complaints and a ruling attributing the defect to the manufacturer

  The OCU (Spanish consumer organisation) has published complaints from owners of BMWs with the N47 engine over timing chain breakage, including refusals by BMW to cover the repair on the grounds that the servicing had not been carried out at an official dealer. A Spanish specialist outlet also cites a 2018 court ruling that is said to have attributed the defect to the manufacturer, although we have not been able to consult the full text of that decision.^[2][7]