BMW 5251 Service Manual page 127

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Cylinder ~ e a d ~ e r n o v a l and Installation
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Remove VANOS unit:
Remove engine lifting eye.
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Remove VANOS mounting nuts (arrows) and pull VANOS
unit and metal gasket off.
CAUTION-
Do not crank the engine with VANOS unit removed. Pis-
tonhalve inteiference may result.
NOTE-
The VANOS unit will contain a small quantity of oil. Place
shop towel to catch oil as unit is removed or tilted.
CAUTION-
If the VANOS adjustment unit is replaced, or if operations are
completed that may change the timing of the camshafts, the
camshaft timing must be checked. See 11 7Camshaft Timing
Chain.
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Remove primary camshaft chain tensioner cylinder (arrow).
CAUTION-
Primary camshaft chain tensioner is under spring pressure.
Press down on secondary chain tensionerand lock into place
using BMW special tool 11 3 291, or a thin drifl or pin.