The VANOS units must be adjusted with special tools and it is advisable to have this done by a BMW dealer. Before removing the units, it's necessary to place the crankshaft and camshafts at TDC for No 1 piston. Then, just screw out the timing chain tensioner and throw away a sealing ring. Remove the retaining bolt from the center of VANOS adjustment unit then rotate sensor gears downward and withdraw each unit from every camshaft. Pull the chains as you take off the units. When fitting make sure that crankshaft and camshafst are still at tdc for no 1 cylinder. Position VANOS units on camshafts paying attention to identifying marks. Install bolts retaining VANOS unit but tighten only until they contact sensor ring surface. Adjust tensioner blade using BMW tools so that timing chain sits properly against it and attach BMW tool No 11 4 290 to cylinder head making pins engaged in corresponding holes of sensor ring gears. Pre-tension guide of chain tensioner tight both VANOS adjuster unit bolts .Take off fittings install tensioner piston with a new sealing ring . The rest of installation is reverse process of removal ,including valve cover installation but before engine start remove crankshaft locking tool first . In order to replace VANOS solenoid valves, take off plastic cap located in cowl trim panel along with fastener centered in cowl . Remove bolts located on each external end of supports shifting supports sideways . Turn back screws in rear part of engine compartment and get rid off filter cover for passenger compartment air circulation system . Release catches take off plastic covers from behind suspension turret-. Press clips pull forward cable guide- Unlatch unbolt then slide cabin air filter lower housing frontwards and work it out- Take away engine cover disconnect solenoid valve wiring connectors-. Get rid of hold down bracket bolts substitute solenoids using fresh rings for sealing-Before installing, compress the piston of chain tensioner to remove any oil.