What is VANOS and Variable Valve timing?

"BMWs VANOS Explained"

We shall attempt to explain the fundamentals of VANOS in this essay. VANOS is an abbreviation for VAluable Nockenwellensteuerung (which translates from German to English to variable camshaft control).

It is a system that was first designed by BMW for cars manufactured between 1992 and 1996.

There are two types of VANOS, single and double. The M50 was the first engine to feature VANOS was(found in a variety of models), double VANOS first appeared in the S50B32 (used in the M3 Evo,M52, Z3M and Z4M) in 1996.

When the camshafts are moved relative to the driving gear, VANOS, a variator system, alters the valve timing. The timing relationship between the intake and exhaust valves is altered.

Why do you need variable valve timing on an engine?

A significant portion of the engine's efficiency and general health is dependent on the valve timing and its performance. Incorrect valve timing may significantly diminish your engine's performance and rob you of fuel economy.

For instance, if the timing is adjusted wrong, the engine may suffer damage. If you're fortunate, all you'll need to do is rebuild it to get it back on track.

When the automobile is travelling at a high rate of speed, the engine's intake valves must open quicker, earlier, and often for a longer amount of time. This is because the engine must generate more power more quickly in order to maintain the pace.

So what is valve timing?

Valve timing refers to the system that controls the exact timing of engine valves opening and closing. To operate an engine accurately and effectively, the engine valves must open and shut precisely at the specified periods.

The two primary valves of an automobile engine are the intake valves, which enable air to enter the engine, and the exhaust valves, which exhaust it.

Our video feature on Camshafts explains the importance of timing.

If the valves open at the incorrect moment, the piston may collide with them, bending them.

What is single VANOS

The first version (renamed retroactively "single VANOS") was employed only on the intake camshaft. Single VANOS adjusts the intake camshaft's position relative to the crankshaft mechanically and hydraulically.

The position is modified in relation to the engine speed and the location of the accelerator pedal. At low speeds, the intake valves open later, contributing to the engine's famous smoothness and also aiding the idling.

What is VANOS, what purpose does it serve, and how does it work? What sort of problems do you get when VANOS starts to fail?

What is VANOS, what purpose does it serve, and how does it work?

Improved speeds force the intake valves to open sooner, resulting in increased torque, reduced fuel consumption, and reduced emissions (this is because the exhaust gases re-circulate inside the combustion chambers).

VANOS gear is totally retracted at idle and has no effect on valve timing. The solenoid is actuated when you step on the gas pedal and begin moving through the RPM range, forcing the oil through the system.

At high speeds, the intake valves reopen. This facilitates the attainment of full power.  As oil pressure increases, the VANOS gear begins to insert itself between the cam gear and the cam. As a consequence, the intake and exhaust valve positions overlap, allowing for exhaust gas recirculation, which reduces emissions at highway speeds.

What is double VANOS?

While double VANOS operates similarly to single VANOS, while the single system utilises two fixed points within the RPM range, the double system utilises a continual adjustment based on speed and accelerator pedal position.

Double VANOS is also applicable to the exhaust camshaft. As a consequence, torque is boosted more and emissions are improved further.

While VANOS is generally dependable, age-related issues may need maintenance. The most often seen issue is a rattling in the top valve train component.

If the engine of a car you are buying has a mileage of approximately 100k, use caution while purchasing as this is likely to be an issue.


The only way to avoid seal failure is to replace them using aftermarket components. The second significant issue is that the piston seals may fail.

This is related to the vehicle's age and mileage. Again, prevention is preferable than cure, therefore if the engine has a high mileage, be certain to replace the piston seals.

We suggest replacing the VANOS seals every 50,000 miles or if you experience any of the following concerns, which may be an early warning sign of future problems.

Single VANOS is found in the following engines:

Double VANOS is available in the following the engines:

Please remember that some variances in the specification appear in the US models.

Common VANOS problems & Diagnosing them.

These are the most common symptoms and problems caused by a faulty VANOS system in your BMW.

  1. Loss of power at low RPM
  2. Reduced fuel economy
  3. Stalling in cold weather
  4. Issues with cold starts
  5. Increase in fuel consumption
  6. Rough idling
  7. Hesitation and flat spots at low RPM
  8. Engine misfires
  9. Check engine light may illuminate

You might get the following diagnostic codes indicating a VANOS issue when you run a diagnostic.

  • P1397: Camshaft position sensor B
  • P1523: Camshaft position actuator is jammed, exhaust
  • P1520: Camshaft position actuator, exhaust
  • 2A82: Vanos intake solenoid
  • 2A87: Vanos exhaust solenoid

Written by Matt Ayling (a.k.a. forum member Prince)

Some of these problems and issues can also be caused by other problems, especially in a tuned car, so please watch our video that deals with diagnosing engine problems further.

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One Response to “VANOS explained”

  1. Nicole says:

    Hello there,
    thanks for the good information , it helped me alot with purchasing my BMW 320i(2200cc) and ensuring I service it well !
    Thanks again!

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