Your BMW builds on a legacy of precise engineering and proud craftsmanship. It all adds up to a driving experience that sets BMW apart: no one laughs when BMW boasts of making The Ultimate Driving Machines.
But even the best-engineered automobiles have a weakness or two, as some owners of BMW N20 engines know all too well. Issues with the engine’s timing chain have affected that model from the start, and while they were eventually mitigated in later versions of the N20, engines built between 2011 and 2015 are still highly susceptible to timing chain issues. We’ll take a look at what the timing chain does, where it tends to fail in certain N20s, and what BMW owners can do about it.
The BMW N20 Engine in a Nutshell
When BMW introduced the N20 in 2011, it marked the first time the company sold a four-cylinder engine in the North American market since the 1990s. The N20 was intended as a more efficient successor to the six-cylinder N52, introducing a turbocharger to achieve similar performance. While some BMW fans had questions about the seemingly less powerful design, the N20 quickly earned a reputation for its smooth delivery of output specs that reminded drivers quite a bit of the N52.
Along with turbocharging and direct injection, the N20 retained the N52’s variable valve timing in an effort to consistently squeeze every bit of power from four cylinders. The new design’s timing components were under more stress than ever, and in early versions of the N20, that stress often showed.
The BMW N20’s Timing Chain Issues
Timing chains in any engine keep components in sync, from valves to the camshaft. The N20’s timing chain has developed a reputation for premature wear and failure, with consequences ranging from decreased power to outright engine failure. Because the N20 is an interference engine, the valves can theoretically meet the pistons. When that happens, your engine is wrecked…and it can only happen if your N20’s timing chain stops doing its job.
The most common cause of timing chain issues in the N20, particularly those produced in the engine’s first four years, has to do with the timing chain guide. The guides installed on original N20s were prone to breaking, which introduced slack to the timing chain and prevented it from doing its job. After a fair bit of wrangling with its customers, BMW issued a recall on N20s produced between 2011 and 2015, allowing owners to refit their cars with a redesigned timing chain guide.
Less commonly, the N20’s timing chain tensioner can also fail prematurely. This introduces the same problem as a broken timing chain guide: the chain has just a tiny bit more distance to travel, and the engine’s millisecond-precise synchronization is thrown off.
N20 owners can unwittingly contribute to the problem, too. Although the tensioner does not depend on oil pressure to work, operating an N20 on low oil, or waiting too long to perform oil changes, can cause friction that accelerates wear on the chain guide or tensioner.
How to Spot BMW N20 Timing Chain Issues
Timing chain problems are almost never catastrophic right off the bat. Here are the most common symptoms of a failing timing chain: they can be subtle, but they’re worth taking seriously.
Your BMW should idle smoothly, and timing chain issues are a primary cause of hiccups at idle. Over time, the same issues can lead your engine to misfire—a more pronounced symptom of the same problem. In this case, you should see one or more fault codes; we’ll cover those toward the end of this article.
Rattling noises or whining
A rattling noise from the front of your engine can be a sign of a slack timing chain. Whining can, too. Although many drivers associate whining sounds with worn serpentine belts, a system that’s out of sync can cause the same telltale slippage and noise. If you notice a whine at around 4,000 RPM, you should probably start by checking your timing chain.
Any automobile engine can suffer from reduced performance for a variety of reasons. Timing chain issues are just one of those, and they often show up at first as reduced acceleration. You might also experience a progressive loss of power at higher speeds, though performance issues related to the timing chain are typically accompanied by rough idling or odd noises.
Fault lights and codes
Don’t ignore your fault lights. If the engine management system has detected a problem with your timing chain, it may throw you a check engine light warning and record a set of fault codes. We’ve included a list of fault codes at the end of this article to help you pinpoint the issue, but the important thing is to get your BMW to the shop as soon as you see a fault light.
What to Do About BMW N20 Timing Chain Problems
Inspection and Analysis
As soon as you notice a problem with your N20 engine’s timing chain, you should have your car inspected by an experienced mechanic. A shop that’s seen its share of BMWs will start by testing the timing chain’s tension and examining its tensioner and guides before looking at other components that might be involved.
To get a quick sense of how much slack is in your timing chain, you can examine it yourself with a clean metal pick by removing the oil cap. The timing chain guides are also easily visible at this point, though inexperienced DIYers might not be able to tell a worn guide from a fresh one. None of this initial inspection takes the place of a thorough examination by an experienced mechanic.
Replacing the Timing Chain
If problems with the guides or tensioner have caused the timing chain to wear down, the prudent way forward is to replace the chain, guides, and tensioner, along with associated sprockets and other ancillary components. This is a job for professionals: the engine will need to be partially disassembled in a particular sequence, and it is all but impossible to efficiently replace the timing chain without specialty equipment.
Off-brand oil filters and other common parts can work just fine, but your timing chain is more finicky. We strongly recommend using a genuine BMW chain or an OEM alternative from an established manufacturer.
N20 Preventive Maintenance
If your N20 was produced before 2016, the best preventive maintenance is probably to have its timing chain replaced, whether or not you’ve experienced problems. N20s manufactured after 2015 have a much better track record in this regard. In any case, regular oil changes using high-quality oil and filters are the best way to avoid the catastrophic problems that a worn timing chain can cause.
Diagnostic Codes for Curious BMW N20 Owners
If you own a diagnostic code scanner, or know how to read the codes recorded by your BMW, you can get a good amount of information about your suspected timing chain issue. Two codes in particular frequently point to the timing chain problems common to the N20.
131501: Slack timing chain
The full version of fault code 131501 officially reads “VANOS, intake, starting from cold: Non-adjustable.” In plain English, this means that VANOS—BMW’s variable valve timing system—is suffering from a slack or otherwise malfunctioning timing chain.
120408: Valvetronic system
BMW’s Valvetronic system controls the engine’s intake valve lift, fine-tuning it for better fuel efficiency, reduced emissions, and better performance overall. Fault code 120408 indicates an internal problem with the Valvetronic system, which includes problems associated with a slack timing chain.
Looking To Repair Your BMW N20 Timing Chain in Connecticut?
If anything in this article reminds you of your N20-powered BMW, we hope you’ll give Paul’s Auto Repair a call. Aside from its timing chain issues, we really like the N20, and we’ve worked on plenty over the years. We’d love to help you experience your BMW in its full glory, and to keep you on the road for years to come.