VANOS systems are durable, but they need maintenance and attention once worn
What causes the fault?
Though VANOS is effective and improves these engines’ drivability, power and economy, as can often be the case, BMW’ s accounting department drove down costs. In doing so, it created a few flaws that reveal themselves as the miles increase. The material used for the seals in the hydraulic units wasn’ t of a specification that could cope with the pressures, oil chemicals and temperatures. Over time, these break down and will result in laggy VANOS performance or complete failure. The systems also rely on closely-toleranced bearings within the splined shafts, which wear and develop the aforementioned nasty rattle at certain RPM ranges.
How to fix the fault in detail?
There are some great products on the market for refreshing and upgrading spline-type VANOS units of all shapes and sizes. The solution is to disassemble the entire unit, inspect all of the components, individually test the solenoid valves and thoroughly clean everything before reassembling with upgraded parts.
Beisan Systems has been creating some excellent parts to repair VANOS units since 2007. It provides suitable seals and gaskets that can actually endure the stresses of the high-pressure, high-temperature oil, and last far longer than the factory-specified seals.
62 The Engine Rebuilder Issue 01