Which BMW Engines Are Most Prone to Timing Chain Failure?
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If you’ve spent any time researching used BMWs, you’ve almost certainly come across warnings about timing chains. It’s one of those topics that can make even straightforward buying decisions feel complicated. But not all BMW engines have the same risk, and some of the most-searched engines, like the B48, the B58, and the BMW B47 engines, are significantly more reliable in this area than the engines that gave BMW the reputation in the first place.
This guide ranks the most commonly discussed BMW engines from worst to best when it comes to timing chain risk.
What Is a Timing Chain and Why Does It Matter?
The timing chain is a metal chain inside the engine that links the BMW crankshaft (which is turned by the pistons) to the camshafts (which open and close the valves). Everything has to happen in a precise sequence. If the chain stretches, slips, or snaps, that sequence breaks down.
On most BMW engines, this is an interference engine, which means the pistons and valves occupy the same space at different moments. If the timing goes wrong, they collide. The result is almost always severe internal damage: bent valves, damaged pistons, broken camshafts. Repair bills regularly run to £3,000 to £8,000 or more. Sometimes the engine can’t be saved at all.
The good news is that timing chain failures are almost always preceded by warning signs, usually a rattling noise on cold start. The bad news is that some BMW engines give very little warning before catastrophic failure, and some are positioned so awkwardly inside the engine bay that even a diagnosis requires significant labour.
The Rankings at a Glance
Each Engine Explained
BMW N47 — The Worst Offender
The N47 is the diesel engine BMW fitted to 1, 3, and 5 Series cars from 2007 to around 2014. It’s the engine in 118d, 318d, 320d, and 520d variants, among others.
The timing chain sits at the rear of the engine, between the block and the gearbox. BMW put it there because they assumed the chain would never need replacing. They were wrong. The chain stretches prematurely, the plastic guide rails crack, the tensioner weakens. The rattle you hear is from the rear of the engine bay, not the front. Replacement almost always requires the engine to come out. Cost: £2,000 to £4,000 before any internal damage is factored in.
Pre-2011 engines, particularly the N47D20A from 2007 to 2009, are the highest risk. BMW improved the chain from around 2011 onwards, but the fundamental design never changed. Some post-2011 engines have failed too, especially on cars with stretched service intervals. If you own one, change the oil every 8,000 to 10,000 miles and listen for any rear rattle on a cold start.
BMW N20 — Petrol Four-Cylinder, Chain at the Front
The N20 is the 2.0-litre turbocharged petrol engine found in 320i, 520i, X3 28i, and similar models from 2011 to around 2017. Unlike the N47, its chain is at the front of the engine, which makes access easier. That difference in positioning saves a significant amount in labour costs if things go wrong.
The problem was the plastic timing chain guides. They degraded prematurely on many cars, causing a distinctive high-pitched whining or whirring sound from the front of the engine. BMW acknowledged the issue and issued an extended warranty, but most affected cars have long since aged out of that coverage. The main risk period was pre-2015 production. BMW switched to metal guides on later builds, which resolved the issue.
The N20 was replaced by the B48 engine in 2015, which fixed the problem properly.
BMW N43 — Petrol Four-Cylinder, Oil-Sensitive Chain
The N43 is the naturally aspirated 1.6 and 2.0-litre petrol engine in 116i, 118i, 120i, 316i, 318i, and 320i cars from 2007 to 2013. It uses a cassette-style timing chain assembly with plastic guide rails. If the oil isn’t changed regularly, the plastic guides degrade and shed debris into the oil system. That debris can block the oil pickup, which leads to oil starvation and the kind of damage you’d rather not think about.
The saving grace is that the N43’s chain failure is almost always oil-related rather than a structural design fault. Cars that have been properly maintained on 8,000 to 10,000 mile oil change intervals rarely develop the issue. It’s a concern, but a manageable one with good servicing history.
BMW B47 — Diesel Four-Cylinder, Improved but Not Perfect
The BMW B47 engine replaced the N47 from 2014 onwards and is found in the current 118d, 318d, 320d, 520d, X1, and X3 diesels. BMW learned from the N47’s failure and made meaningful improvements, better chain materials, stronger tensioners, updated guides, and improved oil feed to the chain area.
However, the chain is still at the rear of the engine. The fundamental access problem didn’t go away. There have been confirmed B47 failures at very high mileages, particularly on cars with extended oil change intervals. The majority of well-maintained B47s don’t develop chain problems, but it’s not a risk-free engine either. The same rule applies: short oil change intervals with approved oil, and listen for any cold-start rattle from the rear.
BMW B48 — Petrol Four-Cylinder, Properly Fixed
The B48 engine replaced the N20 from around 2015 and powers the 320i, 330i, 520i, X3 20i, Z4 20i, and many other petrol models. It was designed with the lessons of the N20 clearly in mind.
Early B48 engines used a two-part timing chain assembly. BMW updated this in 2018 (the ‘B48TU’ technical update) to a single one-piece chain design, which is more durable. The B48 does not have the guide failure issues that plagued the N20. Timing chain problems are not a documented concern on this engine, and given that the Toyota Supra also uses a version of the B48, it’s passed some serious scrutiny beyond BMW alone. It’s widely considered one of BMW’s more reliable modern engines.
BMW B58 — Petrol Six-Cylinder, Highly Reliable
The B58 engine is the 3.0-litre turbocharged straight-six found in the 340i, M340i, 540i, X5 40i, Z4 M40i, and more. It has won Ward’s 10 Best Engines award multiple times and is widely regarded as one of BMW’s best modern engines.
Timing chain failure is simply not a known issue on the B58. There are no widespread reports, no technical service bulletins specifically addressing chain problems, and no pattern of failures in the owner community. This engine has a strong reputation, and it’s earned. If you’re looking at used BMWs and the B58 is an option, the timing chain concern is not a reason to hesitate.
BMW B37 — Three-Cylinder, Solid Track Record
The BMW B37 engine is the three-cylinder 1.5-litre petrol unit found in the 116i, 118i (some variants), Mini, and Toyota Supra base model. Being part of the same modular B-series family as the B48 and B58, it shares the same improved engineering philosophy. No notable timing chain problems have been documented in the owner community. It’s not an engine many BMW enthusiasts focus on, but it’s a reliable unit.
Buying Used BMW Engines with Confidence
If you’re looking to buy a used BMW engine, whether as a replacement after a failure or for a project, knowing the engine code matters more than just the model badge. A post-2011 N47D20C is a meaningfully different engine from an N47D20A. A post-2018 B48TU has a better chain than an early B48. Always confirm the exact engine code before purchasing.
MT Auto Parts stocks genuine used BMW engines for sale across the F, G, and U generation range, covering B48, B58, B47, B57, and related units. Every listing includes the full engine code, mileage at removal, and donor vehicle details. Free VIN matching before dispatch confirms the right specification for your car. Most parts carry a 30-day warranty (T&Cs apply), with delivery to UK mainland addresses within 24 to 48 hours.
Frequently Asked Questions
Is the BMW timing chain problem fixed on newer engines?
Yes, substantially. The N47 diesel and N20 petrol engines from 2007 to 2015 are where the reputation comes from. The B-series engines that replaced them, the B47 diesel, B48 petrol, and B58 petrol, all received significantly improved chain systems. The B48 and B58, in particular, have no documented widespread timing chain issues. The B47 is improved over the N47 but still rear-mounted, so regular oil changes remain important.
What does a timing chain failure sound like on a BMW?
The most common warning is a metallic rattling or clattering noise on a cold start. On an N47, it comes from the rear of the engine bay, the firewall side, closest to the windscreen. On an N20, it’s more of a whirring or grinding from the front of the engine. The noise often settles once the engine is warm, which is why many owners dismiss it. Don’t. If you hear it, get it inspected promptly.
Which BMW engine should I avoid if I’m worried about timing chain problems?
The N47 diesel, particularly pre-2011 builds with the N47D20A engine code, carries the highest risk. If you’re buying an older 1, 3, or 5 Series diesel, this is the engine to be most cautious about. The N20 petrol from before 2015 is the second concern. If you want to avoid timing chain risk entirely, focus on B48, B58, or B57-powered cars from 2015 onwards.
Does the B48 or B58 engine have timing chain problems?
No significant ones. The B48 had a minor early issue with a two-part chain design that BMW addressed with the 2018 Technical Update (B48TU), switching to a single one-piece chain. The B58 has no documented timing chain problems at all. Both are considered reliable in this regard and are regularly cited as among BMW’s better modern engines.
How do I find out which engine is in my BMW?
The quickest way is to enter the last seven digits of your VIN at realoem.com — this is BMW’s own parts lookup system and returns the exact engine specification for your car. The engine code is also stamped on the block itself. Your V5C registration document will show the engine capacity and fuel type, which, combined with the model and year, narrows it down, but the VIN lookup gives you the definitive answer.
Disclaimer: This article is for general guidance only. Timing chain risk, failure patterns, and repair costs can vary by BMW engine code, build date, mileage, service history, and market specification. Always confirm the exact engine fitted to your vehicle by VIN before making buying, maintenance, or repair decisions. MT Auto Parts is an independent BMW car breaker and is not affiliated with BMW AG.
