BMW 5251 Service Manual page 205

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Cylinder Head and valvetrain1
Double VANOS secondary timing chain components,
installing
(M52 TU, M54
engine)
<
Secure camshafts in TDC position using BMW special tool
set 11 3 240.
4
If necessary, turn camshaft so that special tools are squarely
seated on cylinder head.
4
Lift timing chain and hold under tension