The VANOS unit is a system devised by BMW that allows for variable timing adjustment while driving under different conditions. It works on the engine's oil pressure and continuously adjusts as the engine runs.
So, what exactly goes wrong with the VANOS unit? The adjustment mechanism in the vanos has a set of seals that hold the oil pressure and enable the piston that adjusts the cam to function and alter the cam position. The BMW factory installed seals are made of BUNA material and this material is not very resistant to oil and temperature fluctuations. The units are also prone to wear and can develop a rattle if the play isn't removed from their internal parts. We install ungraded Teflon seals to replace the old worn BUNA seals.
Is my VANOS unit faulty? The original seals from the BMW factory were good for approximately 20k miles and after that, the seals hardened and lost their ability to function efficiently (if at all). The chances of your unit being faulty are quite likely if your car has any substantial amount of mileage on it. If your car has a vanos rattle, then this will cure that problem, too.
What are the symptoms of a faulty VANOS? The vanos system contributes to a number of factors that control the peak running of your M50/M52/M54 motor. Some of these symtpoms of failure can include:
- Increase in fuel consumption
- Bogging or hesitation under 3,000 RPM
- Sudden power surge at approximately 3,000 RPM
- Louder idle / vanos rattle
- Loss of torque in the lower RPM range
Why should I replace it now? You may not be aware of some of these symptoms as the car may have had one or more of these problems from the time you bought the car. Replacing your vanos unit can result in an improvement of the running of your car and significantly improve the responsiveness if the seals are in fact faulty. Replacing this part can take hours to complete and the cost of the gaskets that will need to be replaced at that time make this a great time to purchase. Why not replace it while the part is already off the car and while you've already got a gasket set to put everything back together?
Purchasing a VANOS unit from the BMW dealership costs upwards of $600 and does grant this same benefit; however, the dealership uses the original seals and does not prevent failure in another 20k miles.
What does the VANOS cost?
Single vanos without the purchase of a cylinder head - $200.00 plus $50.00 core charge
Single vanos with the purchase of the matching head - $175.00 (head core refunded with return of head and vanos)
Dual vanos without the purchase of a cylinder head - $245.00 plus $100.00 core charge
Dual vanos with the purchase of the matching head - $220.00 (head core refunded with return of head and vanos)
It is important to note that when you purchase this rebuilt vanos unit, it is normal for the car to take ~100 city driving miles to properly bleed the vanos after replacement before the optimum results are felt. Also, a change in fuel consumption might not be noticed until at least a week after the replacement as the car takes some time to re-learn and once this occurs only then can the changes be fully recognized.