Is your BMW engine making a rattling sound? Does it sound like metal is clanking under the valve covers? If you answered yes to any of these questions, you may be in need of BMW VANOS repair.
What is BMW VANOS?
VANOS is BMW’s answer to variable valve timing. It is a combined hydraulic and mechanical camshaft control mechanism managed by the car’s Digital Motor Electronics (DME) engine management system. The VANOS unit is mounted directly on the front of the cylinder head and adjusts the intake camshaft timing from the retard to the advance position.
At the lower end of the engine speed scale, the intake valve is opened later, which improves idling quality and smoothness. At moderate engine speeds, the intake valves open much earlier, which boosts torque and permits exhaust-gas recirculation inside the combustion chambers, thus reducing fuel consumption and exhaust emissions. Finally, at higher engine speeds, the intake valve opening is once again delayed so that full power can be developed. BMW VANOS operates on the intake camshaft in accordance with engine speed and accelerator pedal position.
Benefits of BMW VANOS:
- Enhances Emission Management
- Increases Torque & Output
- Offers Better Fuel Economy
BMW introduced the first VANOS in 1993 on the M45 engine utilized in the 5 Series models. The current rendition of BMW VANOS is double-VANOS, which is used in the M3 models.
Double-VANOS adds an adjustment of the exhaust camshaft as well as the intake camshaft, significantly improving torque. In order to modify the camshafts promptly and precisely to assure improved torque at lower engine speeds and improved power at high speeds, the double-VANOS needs extremely high oil pressure. The high oil pressure allows for quick and precise positioning of the VANOS and engine timing
3 Things That Make BMW VANOS Work:
1. Oil Pressure
The most IMPORTANT thing to remember on BMW VANOS systems, no matter which version, evolution, or update – LOW OIL SERVICE INTERVALS!
BMW dealership service advisers recommend changing the oil every 15,000 miles. This is ridiculous! Oil changes every 15,000? Only a complete knucklehead would recommend changing the oil every 15,000 miles! This is what happens to engines that have such high oil change intervals:
NOT a very pretty sight. Your car deserves better than this! Again, it is important that good clean oil and oil condition is what operates the VANOS. The VANOS’s mechanical operation is TOTALLY dependent on good engine oil pressure! Which means clean oil. The important thing is to use good, synthetic oil.
The formula is simple. GOOD OIL = CLEAN MOTOR
The motor below had 95,000 miles on it, but the customer had J&T Automotive change the oil religiously every 5000 miles.
2. Electronic Components – VANOS Solenoid & Camshaft Position Sensor
The VANOS solenoid is the servomechanism that is instructed by the Digital Motor Electronics system to trigger the engine’s VANOS unit. Positioned at the front of the cylinder head, the two solenoids, one for the intake and one for the exhaust, regulate the flow of oil to the VANOS camshaft exhaust and intake ports.
Signs of solenoid failure can be anything from misfires to harsh running motors or lack of power to poor fuel economy. Solenoid failure typically generates numerous fault codes and activates the check engine light. It is critical to meticulously troubleshoot all fault codes but failed VANOS solenoids are a common problem with BMW motors.
Camshaft Position Sensor (CMP)
This sensor detects the position of the camshaft as it turns and reports the data back to the VANOS.
3. Digital Motor Electronics (DME)
The DME system runs the fuel injection and ignition systems via an isolated control unit. This is a refined computerized engine management system that not only works for racing engines but daily drivers as well.
The DME control unit obtains input indicators from the:
- air mass sensor or intake airflow
- crankshaft pulse sensor
- cylinder identifying sensor
- coolant and air temperature sensors
- exhaust oxygen sensor
- throttle position switch
- the automatic transmission control unit
Optimal fuel amounts and spark timing demands are measured based on sensor inputs and centralized programs which are tuned as needed for every revolution of the engine.
Output signals direct the:
- idle control valve
- fuel pump relay
- fuel injectors
- ignition system
Depending on the type of engine, fuel injectors operate either sequentially or semi-sequentially. Not adjustable are the ignition timing, idle speeds, and air/fuel ratio.