BMW 5251 Service Manual page 186

Cylinder Head and Valvetrain
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Remove oil baffle cover from above intake camshaft(s)
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Rotate engine at crankshaft vibration damper center bolt in
normal direction of rotation (clockwise) until camshaft lobe of
lifter to be tested points away from the lifter, allowing valve to
be completely closed.
Use a plastic or wooden stick to press down on top of lifter
with approximately 3.5 Nm (2.25 ft-ib) of force.
If the lifter collapses slightly as though spring loaded, air
may be trapped in the lifter.
NOTE-
Air trapped in hydraulic lifters may result from oil foaming (air
being drawn in by the oil pump). This may be caused by a
faulty oil pump control valve O-ring; leaking oil pump pickup
gaslcet; or by oil starvation to pump.
Press down on top of lifter for 10 to 15 seconds uslng approx-
lmately 6 to 9 Nm (4.5 to 6.75 ft-lb) of force.
If anv clearance is created between the lifter and the cam-
shafi lobe, the check valve in the lifter is not closing. Re-
place lifter.
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To replace a hydraulic lifter, remove appropriate camshaft.
Refer to camshaft removal procedures given in Camshaft
and lifter removal and installation.
Once camshaft is removed, withdraw faulty lifter(s) and re-
place with new lifter(s). Inspect lifter bores for wear and scor-
ing at arrows.
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Reinstall camshafts. See Camshaft and lifter removal and
installation.