Diagnosing a Failing BMW Vanos System – When to Repair Your Vanos

When to Replace or Rebuild your BMW VANOS System

This guide brought to you by BMW N54 Tuners will explain what the VANOS system is, the importance of the technology, and most importantly when and why it should be replaced or rebuilt. The VANOS system isn’t unique to the N54 engine; it is used in many variations of BMW engines. However, for tuning purposes it is important to at least be able to identify VANOS problems, and know how to fix them as a faulty solenoid can cause a major loss of horsepower.

What the hell is BMW VANOS?

The BMW VANOS (variable nockenwellen steuerung in German) is a variable valve timing technology developed by BMW. The system variably adjusts the timing of the valves by changing the position of the camshaft relative to the drive gear. In simpler terms, it adjusts the camshaft for the intake and exhaust valves, allowing for smoother idling, more torque, and a more elastic powerband. In addition to this, the vanos solenoids control the flow of oil to the cam gears, which is what allows the timing to adjust. Dirty, clogged, or improperly functioning vanos solenoids will have a significant impact on horsepower, performance, and overall drive-ability.

The first inclusion of Vanos was in the 1992 BMW M50 engine that was used in the 5-Series and only adjusted the position of the intake camshaft. Double Vanos was introduced four years later in 1996 in the S50 engine and featured continuous variability of the intake and exhaust valves, rather than only the intake valve like the single vanos had done.

Here are two diagrams that show how VANOS works, if anyone wants to confuse themselves even more:

 

How the BMW VANOS System Works

Why do I need to Understand VANOS?

Well, you really don’t. Understanding the Vanos system and the technical and mechanical ideology behind it is a headache and filled with jargon that only advanced mechanics and ECU tuners need to understand. What’s important to us as BMW owners is knowing that the Vanos system is a major electronic component of our engine’s computer system and that a bad or damaged Vanos can cause a decrease in power and torque, rough idling conditions, and poor fuel economy.

Symptoms of a Bad BMW VANOS System

  • Loss of power and torque, primarily in the lower ranges, typically below 3k RPMS
  • Engine hesitation and bogging in the lower rpm ranges
  • Rough idle with frequent hiccups
  • Increased fuel consumption or poor fuel economy
  • Cold start issues and stalling in cold weather
  • Engine fault codes, aka a check engine light
  • Engine constantly falls into limp mode after acceleration

Vanos Fault Codes:

These are only a few fault codes for the Vanos system, other codes could also indicate a failing Vanos system. If you have a check engine light, we highly recommend buying a code reader and finding out what it is yourself before you pay a shop $100 to plug their scanner into it.

When to Replace a Bad VANOS System

Although there are various symptoms caused by a failing Vanos system, sometimes they are not noticeable at all until the system has just about completely gone bad. Certain engines are good at hiding any symptoms and you may not realize your Vanos has gone bad. Here are a few key mileage points we note:

  • 50,000 Miles: at 50k miles, your Vanos seals are probably just about all worn down. If you do not notice any issues at this point you can go a bit longer without repair, but your car might be performing below par without you knowing.
  • 70,000 Miles: by 70k miles you should repair/replace your VANOS if you have not already. At this point, your seals will be worn out and your car will have less power in the lower ranges, whether or not you notice it.

When you replace your Vanos you will notice an increase in lower range power, up to about 3k RPM’s, you will improve your fuel efficiency by a decent amount, and it may solve any rough idling that your car has (this can also be caused by spark plugs or the spark plug gapping). A lot of the time you won’t notice that your car is underperforming, especially if you haven’t experienced it at full performance, and therefore will be hesitant to repair a part that isn’t technically broken yet. But we recommend replacing the seals and the whole system around 70k miles if not earlier. We consider it preventative maintenance and you will notice a difference in the performance and smoothness of your ride.

Important Note: if you are going to fully replace your VANOS solenoids, I highly recommend using Genuine BMW solenoids, rather than some crappy solenoids you can find on Amazon. The aftermarket brands are significantly less expensive, but are also significantly worse. These solenoids are a crucial component of the timing and overall performance of your BMW/N54 engine. You wouldn’t put 87 octane gas in your N54, would you?

VANOS System Maintenance: How to Clean your VANOS Solenoids

As we mentioned prior, having clogged or dirty vanos solenoids can result in poor oil flow to the cams, and therefore poor timing. You might not want to fork out $300 for some new solenoids, especially if your BMW hasn’t started to experience any of the symptoms to a severe extent, or enter limp mode. The good news is: you can remove and clean your vanos solenoids, and it is relatively easy.

Cleaning your Vanos solenoids is a 30-minute DIY and can be completed by novice tuners. As much as I would love to write a DIY on it myself, I haven’t gotten around to cleaning mine yet, and there is a perfectly good DIY guide on the forums.

BMW VANOS Solenoid Cleaning DIY: http://www.e90post.com/forums/showthread.php?t=486201

 

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Jake

Jake is a BMW enthusiast and owner of http://www.bimmerhq.com. He has been active in the BMW industry and community for years and has a passion for blogging about all things BMW. He currently drives a 2008 BMW 135i and has build plans for 600whp. Follow this blog to keep up to date on his progress!
By | 2017-12-05T22:17:46+00:00 December 4th, 2017|Featured, N54 Maintenance|0 Comments

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