Volvo VNL Operator's Manual page 294

Volvo Exhaust Brake
The exhaust brake is standard on the Volvo
D12 engine. It is used to reduce wear on
the brake linings. The exhaust brake is
most effective at high engine speeds (1,500
to 2,300 r/min). The exhaust brake is auto-
matically disengaged if the engine speed
drops to or below 1,100 r/min.
The exhaust brake works by containing the
exhaust gases in the exhaust manifold,
thereby making the engine work against the
back pressure. This provides a retarding
force on the drive wheels.
The exhaust brake is operated by a two-
position switch in the right-hand switch
cluster. For the exhaust brake to function,
the following must be in effect:
•
The switch is ON
•
Accelerator and clutch pedals are fully
released
•
Engine speed exceeds 1,100 r/min
When the cruise control is engaged, the ex-
haust brake automatically engages if the
selected cruise speed is exceeded by ap-
proximately 5 mph (8 km/h). The exhaust
brake is then disengaged when the speed
has returned to approximately 3 mph (5
km/h) above selected cruise speed.
NOTE! For both exhaust and engine
brakes, use a "one gear" driving strategy
when going downhill to keep engine speed
up for effective braking (for example: up-
hill 7th gear and downhill 6th).
Brakes 289
W3001324