Hydraulic Lifters, Checking And Replacing - BMW 5251 Service Manual

Cylinder Head and valvetrain1
Hydraulic lifters, checking and replacing
Self-adjusting hydraulic lifters (A) keep the valve clearances
within a limited working range. Hydraulic lifters are sealed
units and require no maintenance. Section view of camshaft
( 6 ) and valve with conical valve spring
(C)
shown.
Under some circumstances, such as a cold start, the cam fol-
lowers may emit noise. Hydraulic lifter noise is usually a high-
pitched tapping or chattering noise. In most instances, this is
considered normal as long as the noise goes away in a few
minutes (maximum 20 minutes). If the noise does not go
away, either the lifter is faulty or the oil pressure to the lifter is
low. Hydraulic lifter replacement requires that the camshaft
first be removed.
NOTE-
Before checking hydraulic lifters, male sure engine oil is
fresh and at the proper level. Sticky lifters can be the result of
sludge build up in the cylinder head and lifters.
-
Run engine until it reaches normal operating temperature.
Shut off engine.
-
Working inside luggage compartment, disconnect negative
battery cable.
CAUTION-
Prior to disconnecting battery cable, read the baltery dls-
connection cautions given In 001 General Cautions a n d
Warnings.
Disconnecting the battery may erase fault code(s)
stored in control module memory Check for fault codes
4
Remove left and right interior ventilation duct (left side
shown):
Release plastic locking tab (A) or release loclting tabs on
top of duct (later models).
Rotate duct counterclockwise to unloclt from bulithead and
remove (arrow).