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BMW N20 Timing Chain Failure – Symptoms & Solutions

Austin Parsons

Meet Austin

Austin graduated from the University of Colorado Denver in 2021 with a degree in technical writing and remains in the Denver area. Austin brings tons of automotive knowledge and experience to the table. Austin worked as a Technical Product Specialist at BMW for over 5 years and drives a heavily modified E30 325i with a stroker kit, all of which he built from the ground up.

While the N20 is often considered a stout and reliable engine, early versions of the engine have a major flaw with the design of the timing chain guides. The plastic guides are known to disintegrate, allowing excess slack in the timing chain, plastic particles in the oil filter, and excess timing chain wear. The N20 timing chain failure issue can even lead to complete engine failure in some instances. While there is no doubt that timing chain failure is an issue on the N20, it is believed by many BMW enthusiasts, and BMW themselves, that the issue is inflated online.

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BMW N20 Engine Credit: HLW Wikimedia

In this guide, we’ll cover everything that you need to know about the infamous BMW N20 timing chain failure issue. We’ll look at what causes the failure, as well as the common symptoms, preventative maintenance, and fixes/repair costs associated with it. 

For more information about common BMW N20 engine problems, take a look at our N20 Common Problems Guide. We also have a dedicated N20 Engine Page where you can learn almost everything about the inline-4 including specs and popular modifications. 

What Causes BMW N20 Timing Chain Failure?

Timing chain failure is one of the most reported issues when it comes to the N20 engine. That’s a pretty big deal, as the timing chain is one of the most critical components of the engine’s operation. The N20’s timing chain is responsible for synchronizing the engine’s crankshaft and camshaft, ensuring that the intake and exhaust valves open and close at the right intervals. It’s an even bigger deal on the N20, as it is an interference engine, meaning that if the engine isn’t timed properly, the pistons can make contact with the valves, essentially killing the engine.

The N20 has less of a timing chain issue and more of a timing chain guide problem. The N20’s timing chain guides are responsible for guiding the timing chain along its route to the crankshaft and camshaft, ensuring that there is no play in the chain. Early N20 timing chain guides were made of a plastic/polymer substance and featured a subpar design. As a result, the timing chain guides on many 2011-2015 N20 engines ended up disintegrating, leading to excessive play and slack in the timing chain. The play and slack could then cause the engine to skip timing dramatically, leading to the pistons coming in contact with the valves.

Outside of the timing chain guide issues, the N20’s timing chain was also susceptible to other issues, mainly caused by improper maintenance. Low engine oil is another common cause of N20 timing chain failure due to the chain not being lubricated properly. The lack of lubrication can cause excessive friction on the chain itself, causing it to wear quickly. 

Which Vehicles Were Affected?

Timing chain failure is most common on N20-equipped BMWs that were produced between 2011 and the beginning of 2015. In January 2015, BMW redesigned the N20’s timing chain guides, which significantly improved their reliability. N20-equipped BMWs produced after 01/2015 received the new timing chain guides and have a much lower failure rate than the earlier cars.

BMW N20 Timing Chain Failure Symptoms

  • Loud whining from the engine
  • Significant scoring on the timing chain
  • Too much timing chain slack/play
  • Misfires/rough idle
  • 131501 and 120408 fault codes

In almost every case, there is some kind of warning sign before an N20 timing chain fails completely. Fundamentally, the problem is caused by either too much slack/play developing in the chain, or the timing chain itself wearing at a rapid rate. In both cases, there are some pretty noticeable symptoms. If the timing guides have failed and excessive slack has built up in the chain itself, a clicking or rattling noise is a telltale sign. If the guides are beginning to fail, they tend to let off a very noticeable and pronounced whine around 4,000 RPM.

Characteristic N20 Timing Chain Guide Whine

Outside of strange sounds, there are some other, more concrete, symptoms of early N20 timing chain failure. Since the timing chain is responsible for keeping the engine in time, excessive wear or play can also cause misfires and engine codes. 131501 (Variable camshaft timing control (VANOS) intake) and 120408 (Charging pressure control: Switch-off) are the two most common DTCs associated with N20 timing chain failure, with the former concerning the VANOS system and the latter concerning the Valvetronic system. The 131501 code is truly the one to pay attention to, as it is a very common code stored in the DME when the timing chain gains slack.

In combination, these are the symptoms that you should be looking out for when it comes to N20 timing chain failure. If all of these symptoms occur simultaneously, it is pretty safe to assume that your engine’s timing is off.

Can You Prevent BMW N20 Timing Chain Guide Failure?

The best way to prevent N20 timing chain failure is by staying on top of scheduled maintenance. As I mentioned in the previous section, one of the main causes of timing chain failure on the N20 is a lack of lubrication on the chain itself. It is crucial to make sure that your engine oil is always at an adequate level and that the oil itself is fresh. 

Dirty engine oil loses its lubricity, which can also lead to excessive timing chain wear. While BMW recommends that you change your engine oil every 15,000 miles, 5,000-7,000 miles is a better interval to ensure that your timing chain stays in good condition. It is also critical that you are using quality, BMW-approved, engine oil as well. BMW recommends only LL01-approved oils, which you can find a list of here.

Outside of staying on top of oil changes, the only other solution for the problem is to preemptively replace your early N20’s timing chain guides with the updated post-January 2015 guides. That isn’t a cheap option, with a replacement cost of somewhere in the ballpark of $2,500. However, that is a much cheaper option than replacing the engine altogether should the failure occur. 

There isn’t a fail-proof method of preventing timing chain failure on the BMW N20, but staying on top of your oil change intervals and other standard maintenance is the best way to limit risk.

Fixes and Repair Costs

Average BMW N20 Timing Chain Repair Cost: $2,500-$3,000

Since the timing chain is such an integrated part of the valvetrain, it is a pretty difficult component to replace. For that reason, it is also a pretty expensive repair. Obviously, if the timing chain has completely failed, allowing the engine’s pistons to make contact with the valves, it will take a lot more than just a timing chain replacement to fix the engine. In most cases, if the timing chain fails completely, you’ll be looking at a complete engine replacement.

If you do catch the timing chain guides early, a replacement of the guides themselves can cost anywhere between $1,500 and $2,500 at a certified BMW repair center. If there is stretch in the timing chain itself, you will need to change the timing chain and tensioner as well, resulting in a higher repair cost of around $2,500-$3,000. It is possible to find a better price if you shop around for a qualified BMW independent repair shop, but the cost is still significant. Most of the cost comes from the labor required, as BMW typically charges around 10 hours for the replacement.

For enthusiasts who are skilled with a wrench, a DIY repair is also possible. Since timing chain issues are such a common issue on the N20, there are a ton of detailed guides on repairing the issue at home. It is important to mention that an N20 timing chain kit costs around $650 from a reputable site and the job requires specialty tools. I’ll leave a link to a video that covers the repair process below.

BMW N20 Timing Chain Failure is a True Issue, If Not a Bit Overblown

Timing chain failure is one of the most commonly reported issues on the inline-4 cylinder engine. With that being said, the N20 is known to be an extremely reliable engine with very few common problems. As a result, the true number of affected engines is relatively low compared to the number of N20s on the streets. In a timing chain failure log poll on Bimmerpost.com, 82% of N20 owners report never having an issue with their engine’s timing chain assembly, which should give some peace of mind. 

The other good news is that timing chain failure doesn’t occur overnight. There are generally some pretty apparent warning signs before the timing chain gives out completely. Rattling or whining is generally the first warning sign that the chain is gathering slack, usually accompanied by a number of engine codes. If you notice either of those symptoms or both of them in unison, it is a good idea to have your engine inspected.

There are also some steps that you can take to help prevent timing chain failure. The most important preventative step that you can take is staying on top of regular maintenance. Frequent oil changes with high-quality BMW LL01-approved oil can go a long way toward preventing issues. If you own an early-model N20 BMW, you can also preemptively swap out the early timing chain assembly with the updated parts from after January 2015.

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