Volvo Penta D4 Operator's Manual page 68

Maintenance
66
Drive Belt, Check and Change
WARNING!
Stop the engine before doing any maintenance work.
General
Check belt tensions and condition regularly. A belt that
is tensioned too tightly may damage bearings, while a
belt too-loosely tensioned may slip.
Check and adjust the belt after operation, while the belt
is still warm.
IMPORTANT!
Always replace a belt that appears worn or has cracks
(belts that work in pairs shall always be changed
together).
Adjusting/replacement of drive belts
The standard alternator and water pump are driven by
a poly-V belt for the best function and lifespan.
Replace/tension the belt as follows:
1 Loosen the screws (1) on the tension roller bracket.
Remove and replace the belt as required.
2 Tension the belt by applying a torque to the ten-
sioning roller square fitting (2) of 70 Nm (52 lbf.ft).
Lock the tensioning roller using screws (1). The
screws must be tightened to 50 Nm (37 lbf.ft).
3 Repeat the procedure when the engine is warm:
Loosen screws (1) and tension the belt.
7748934 04-2008