BMW 1989-1995 525i Service Manual page 115

CYLINDER HEAD AND VALVETRAIN
116-17
Hydraulic Cam Followers
(M50/M60 engines)
The M50 and M60 engines use self-adjusting hydraulic cam
followers to keep the valve clearances within a limited working
range. The cam followers are sealed units and require no
maintenance or adjustment. Be sure to inspect the cam fol-
lower bores for wear or scoring.
Under some circum stances. such as a cold start. the cam
followers may become noisy. Hydraulic cam follower noise is
usually a high-pitched tapping or challering no ise. In most in-
stances. 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 followe r is faul ty or the oil pres-
sure to the follower is low. Hydraulic cam follower replace -
ment requires that the camshaft first be removed .
To check hydraulic cam followers
1. Run the engine until it reaches normal ope rating tem-
perature.
2. Turn the engine off and remove the top engine covers.
the ignition coils. and the cylinder head covers.
3. Using a plastic or woode n stick. press down on the top
of the follower. See Fig. 37 . If there is any noticeable
clearance. the lifter is faulty and should be replaced.
Fig . 37. Hydraulic cam follower being cnecke o. Note that cam lobe is
pointing up. (M50 engine shown .)
NOTE-
When checking the lifter. makes sure the camshaft lobe
is
facing up
so
that there
is
no valve spring pressure on
the cam follo wer.
4. If a cam follower is faulty. remove the camshaft and
withdraw the follower as described under Cylinder
Head Disassembly and Assembly.
5.
Cylinder head assembly is the reverse of disassembly.
Tightening Torque
• Cylinder head cover to cylinder head/
timing chain cover
M6 10 Nm (89 in-lb)
M7 15 Nm (11 ft-Ib)
Rocker Arms and Rocker Arm Shafts
(M20 and M30 engines)
Rocker arms and rocker arm shaft s are components that
wear and are usually the cause of valve train noise. Although
valve train noise may indicate worn rocker arms or rocker arm
shafts, valve train noise may also be caused by incorrect valve
clearances or other engine wear. Valve clearance adjustment is
described above under Valve Adjustment (M20 and M30 en-
gines only).
First check the rocker arm bushings for wear. If the lower part
of the bushing is shiny and rough. the rocker arm is worn. A
good rocker arm bushing surface will have a dull, smooth finish
all around. Continue checking the rocker arms by installing them
on a known good rocker arm shaft. There should be no notice-
able play in any direction. See Fig. 38. The exhaust-side rocker
arms are the most susceptible
to wear. If the
rocker arm or
shafts show any visible signs of wear, these parts should be reo
placed.
CAUTION-
Some 535i models produced between September
1992 and Aprif 1993 may have faully rocker arms
installed. On vehicles
so
equipped. the rocker arm
bushings can slide out of the rocker arms. causing
the valves to jam at the rocker arm eccentrics and
result in engine damage. Contact an authorized
BMW dealer lor vehicle chassis ranges and addi-
tional information on this service action.
Rocker Arm Specifications
• Radial play .. 0.016 to 0.052 mm (0.0006 to 0.002 in.)
CYLINDER HEAD AND VALVETRAIN RECONDITIONING