BMW 1989-1995 525i Service Manual page 35

MAINTENANCE PROGRAM
020-13
Tensil e b reak
Correct
Too low Too high
Glaz ing
Cracking
Separation
00 1192 1
Fig. 9. Examples of V-belt failure. Court esy of Gates RulJber Inc .
Tighten ing Torques
• Tensioning gear (alternator
belt tensioning) 7 Nm (62 in-lo]
• Tensioning gear (power steeri ng
belt tensioning) 8 to 8.5 Nm (71 to 75 in-Ib)
• Tensioning gear locking nut _ 24 Nm (18 ft-lb)
Replacement of the V-belts every four years is recommend-
ed. Loosen the mounting bolts and adjust until the belt tens ion
is as loose as possible. Remove the belt by slipping it over the
pulleys. In some cases it may be necessary to remove one V-
belt to get to another. Cross secti on and length determine belt
size. Use the old belt for comparison . or make sure that the
new belt fits into the pulley groove. See Fig. 10.
NOTE -
Wilen
belts are replaced with new ones. store the old
set in the luggage compartment lor emergency use.
When installing a new belt. gently pry it over the pulleys.
Too much force may damage the belt or the accessory. Ten -
sion the belt(s). run the engine for a few minutes (at least 1500
rpm). then recheck the belt tension.
.
Fig . 10. Cross-section of correct V-belt position In pulley. Courtesy of
Gates Rubber Inc.
CAUTION -
0 0
not over tighten the
v-betts.
Overtlghtenmg will
cause shaft bearings to fail prematurety
Poly-ribbed belts, check ing and replacing
(M50 and M60 eng ines)
The automatic-tensioning poly -ribbed belt(s) should be in·
spected during regular maintenance interva ls. Inspect the belt
with the engine off. Twist the belt to inspec t its sidewalls and
bottom. Belt structural dam age . glazed or shin y contact sur-
faces . cracking. or oil contamination are all reasons to replace
a belt.
To replace the belt on M50 motors. first pry out the cover
from the front of the belt tensioner. Then use an 8mm allen
socket to relieve the tension on the belt. See Fig. 11 . Install
the new belt with the tensioner in the released position. Install
the dust cap to the tensioner once the belt is installed.
8001102 7
Fig. 11. Poly-ribbed dnve belt being removed on M50 engine.
TUI
8
mill hex wrench ciockwee
0
reheve hell tension and then
sho
bel ofi pulleys.
ENGINE COMPARTM EN T MAINTENANCE