This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your BMW 3 Series. The book contains 272 pages of full color projects detailing everything from performance mods to timing the camshafts. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any 3 Series owner's collection. The book was released in August 2006, and is available for ordering now. See The Official Book Website for more details.
The later-model E36 six-cylinder engines have a mechanism that allows for variable advancing of the camshaft timing. The VANOS unit (Variable Onckenwellen Steuerung) is an electromechanical unit that uses a hydraulic piston to accelerate the camshaft timing at higher rpm. This unit is controlled electronically by a solenoid connected to the engine management system (DME).
The VANOS unit is hydraulically operated using pressurized oil from the engine. As such, the oil line that feeds the VANOS unit often begins to leak from age. It's very common for this line to weep oil and leak it on top of the engine. To replace it, you will need to remove the intake manifold first in order to gain access (see our intake manifold removal article). Once the manifold is off, removal of the line is as easy as disconnecting the two banjo bolts on each end, and removing and replacing the line. Use new aluminum sealing rings when you install the new line.
Also accessible is the VANOS unit solenoid. This unit is responsible for actuating a valve that opens and allows pressurized oil to flow into the VANOS unit. To remove and replace this solenoid, you will also need to remove the intake manifold, as the electrical connector for the solenoid is hidden under the manifold. Be sure to use a new O-ring on the VANOS solenoid when you install its replacement.
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This photo shows the two ends of the VANOS oil supply line. On the left, you see the point where it mounts to the VANOS unit. On the right, the line snakes down under the intake manifold and mounts just behind the oil filter housing (yellow arrow). As you can see, the oil line has been leaking and is wet with oil. When installing the new line, use new sealing rings at both ends (green arrows). If you reuse the old sealing rings, they may end up leaking.
This photo shows the removal of the VANOS unit solenoid. The solenoid opens a valve that allows oil into the VANOS unit, which then advances the camshaft timing. Use a 32-millimeter wrench to loosen the solenoid from the VANOS unit housing. The inset on the lower left shows the inside of the solenoid. Use a new O-ring when reinstalling the solenoid. The inset on the lower right shows the valve in the VANOS unit that the solenoid opens. The light blue arrow at the top shows the camshaft position sensor (Project 14). The VANOS solenoid must be removed in order to install the camshaft position sensor into the cylinder head.