BMW 1989-1995 525i Service Manual page 126

8 1113 1
117-6
CAMSHAFT TIMING CHAIN
Fig. 15. Upper timing chain cover mountmq nuts (arrows) on 1991
and 1992 rs.
26 . On 1993 and later cars. remove the two access plugs
from the VANOS control unit. just in front of the exhaust
camshaft sprocket. Remove the exhaust camshaft
sprocket mou nting bolt s (use Torx
E10
socket ).
NOTE -
Hold the camshaft stationary (at hex on camshaft)
when loosening or tightening the camshaft sprocket
mounting bolls.
27. Depress the secondary timing chain ten sioner and lock
it in the dow n pos ition by inserting BMW special tool no.
11 3290. Alternatively. a stiff piece of wire can be used.
See Fig. 16.
28. On 1991 and 1992 ca rs. remove intake an d exhaust
camshaft sprocket mounting bolts using a Torx E10
socket.
29.
On
1993
and late r cars (VANOS). rem ove the six
mounting nuts from the VANOS con trol unit and pull the
control unit from the cylinder head . Remove the intake
camshaft sprocket mounting nuts.
30. Remove both secondary sprockets toget her with the
timing chain from the front of the camshafts. On cars
with VANOS. also remove the thrust washer fro m the
intake sprocket. 1991 and 1992 cars (non-VANOS). re-
move the cylinder identification trigger plate from the
front of the intake camshaft.
CAUTION -
The crankshaft must not be allowed to rotate o nce
the timing cham is removed. The pistons can con-
tact the valves.
CAMSHAFT TIMING CHAIN
Fig. 16. Secondary timing chain tensioner being locked (lawn. Press
tensioner
down fully and insert locking wife through holes
(arrow).
NOTE -
Do not remove the secondary sprocke ts Irom the cham
unfess these parts are being replaced. Wire tie each
sprocket to the cnein to keep the sprocke ts timed to
each other. Keeping the sprockets timed will simplify in-
stallation.
31 .
Remove the sec ondary timing chain tension er.
32 .
Remove the primary timing chain tensione r from the
side of the cylinder head. See Fig. 17.
CAUTlON -
Remove the
tenstoner
plug slowly. There is a long
spring under tension beneath tne plug.
33. Remove the remaining Torx bolt from the lim ing cha in
guide . See Fig.
18.
34. Lift the primary chain sprocket off the exhaust cam shaft
and rem ove the chain.
35.
Inspect the timing chain sprockets. Sprocke ts that have
worn or missing teet h should be replaced . Inspect the
guide rail and tensioner rail for deep grooves caused by
chain contact. Replace any part that is worn.
NO TE -
. /1 any 01the sprockets are being replaced due
1 0
wear.
the chain should also be replaced.
•
/I the crankshaft sprocket requires replacement. the
oil pump dove sprocket and chain must be removed
as described under
119 Lubrication System