The BMW N53 (naturally aspirated) and N54 (turbocharged) engines were among the first BMW engines to come with variable valve timing on the intake and exhaust camshafts. The N53 and N54 straight-six unfairly earned a bad reputation for reliability with technicians due to timing chain and variable valve timing issues. The reputation comes from owners not keeping up with oil changes and having a hard time checking engine timing.
The latest version continuously adjusts the position of the intake and exhaust camshafts for greater power, efficiency and idle performance. The key word to remember for the latest model VANOS systems is that they run “continuously”, and not just below a certain rpm range.
In order to service it, you will need a suitable device for locking the crank and camshaft. You’ll also need a scan tool and binoculars to observe crankshaft and camshaft signals to complete more sophisticated diagnostics.
VANOS
Some newer systems can change camshaft timing by as much as ±72 degrees. The Dual-VANOS system operates at all engine speeds. At lower engine speeds, the VANOS system opens the valves more slowly during the intake stroke, increasing the vacuum and cleaning effect created by the piston moving downwards in the cylinder. This improves idle quality and smooth tip-in power from a stop. As engine rpm increases, the valves open earlier, increasing torque as rpm increases. At higher engine speed, the valves will open more slowly for full power delivery so that the effect of exhaust gas coming out of the cylinder can draw more air into the cylinder. Hot rodders call this “overlapping valve”.
The system can add and even remove the EGR valve by allowing some of the exhaust gas to remain in the combustion chamber to control combustion temperature and NOX emissions.
Additionally, the camshaft position was changed to reduce engine warm-up time by allowing unburned fuel to reach the catalytic converter. When the VANOS system on the N53 and N54 fails, the most common symptoms are poor idle quality, reduced power and poor fuel economy. These symptoms are also common in other variable valve timing systems.
How Does VANOS Work?
Like many variable valve timing systems, VANOS uses an oil pressure powered actuator to actuate the camshaft. Actuators require a consistent supply of oil for the correct viscosity, pressure and volume.
The N53 and N54 use a conventional cam phaser with an internal chamber that holds the pressurized oil that changes the position of the camshaft.
The BMW N53 and N54 use an oil control valve like many other variable valve timing engines. The solenoid is driven by a pulse-width modulated signal.
If the oil is contaminated or has the wrong viscosity, the system can become sluggish. If the oil pressure cannot move the camshaft to the target position within the set time, the camshaft position sensor senses it and sets a code.
Without oil pressure, the camshafts move fully in reverse and get pin-locked. If the actuator and camshaft don’t return to their proper positions because of oil pressure leaking past the seals, a code will be triggered.
Before attempting to measure the crankshaft and camshaft waveforms, make sure to take out the oil control valve. Failing to do so might give the appearance of timing being out of sync as the engine makes adjustments to the camshaft.
What’s Wrong With The VANOS N53 And N54 System?
The main VANOS system failures often stem from oil quality. The primary issue arises when the O-ring seal on the piston deteriorates, permitting oil pressure to move between the chambers. This results in the actuator becoming stuck, either in the forward or full reverse position.
When this occurs, the actuators are unable to counteract the pressure exerted on the camshaft by the valve springs. This can cause crackling sounds on startup and idle.
Using oil of the incorrect thickness can lead to timing corrections either slowing down or speeding up, meaning they may lag or happen too quickly. This adjustment happens within milliseconds. Depending on your scan tool and your ability to access BMW DME or OBDII codes, you might see terms like “stuck,” “stiff,” or “lagging” in the description.
The engine will factor in the oil and coolant temperatures into the time allowed for actuation. If you have code related to this sensor, you may want to resolve this issue before troubleshooting the VANOS system.
Let your customers know that the type of oil they use affects their engine’s timing chain life. BMW suggests using high-quality 5W-30 or 5W-40, fully synthetic oils that meet BMW Longlife-01 FE specs. These oils are designed for longer change intervals. Using low-quality oil can lead to premature wear on timing chain parts.
