Engine Brake Operation - freightliner BUSINESS CLASS M2 Driver Manual

1
10/17/2001
1. Engine Brake On/Off
2. Engine Brake Intensity Switch
Fig. 7.17, Engine Brake Switches
WARNING
The engine brake must be disengaged when
shifting gears using the clutch pedal. If the en-
gine brake is engaged when the transmission is
in neutral, the braking power of the engine brake
can stall the engine, which could result in loss of
vehicle control, possibly causing personal injury
and property damage.
"Control speed" is the speed at which the engine
brake performs 100 percent of the required downhill
braking, resulting in a constant speed of descent.
The control speed varies, depending on vehicle
weight and the downhill grade.
For faster descent, select a higher gear than that
used for control speed. Service brakes must then be
used intermittently to prevent engine overspeed and
to maintain desired vehicle speed.
For slower descent, select a lower gear, being care-
ful not to overspeed the engine. Occasional deactiva-
tion of the engine brake may be necessary to main-
tain the designated road speed under these
conditions.
If the engine is equipped with both cruise control and
an engine brake, the engine brake can operate auto-
matically while in cruise control mode. If the cruise
control/engine brake function is turned on in the
DDEC VI system programming, the engine brake will
come on low when the set road speed increases a
few mph (km/h) above the cruise set speed. The
maximum amount of braking is selected with the
dash switches. When the vehicle returns to the set
cruise speed, the engine brake will turn off.
2
The engine brake will only operate when the accel-
erator pedal is fully released. Depressing the clutch
will also prevent the engine brake from operating.
Vehicles equipped with ABS have the ability to turn
the engine brake off if wheel slip is detected. The
engine brake will automatically turn back on once
wheel slip is no longer detected.
The DDEC VI system will deactivate the engine
brake when the engine speed falls below 1000 rpm
f610588
or when the vehicle slows down to a preset speed,
depending on DDEC programming. This prevents
stalling the engine.

Engine Brake Operation

Depending on the brake type, the engine brake may
be disabled when engine temperature falls below a
set level.
Do not allow the engine to exceed 2500 rpm. Se-
rious engine damage could result.
To activate the engine brake after the engine is
warmed up and the vehicle is in motion:
1. Remove your feet from both the clutch and
throttle pedals.
2. Press the On/Off switch to toggle the engine
brake on. See
engage at the rate last set on the brake intensity
switch.
3. Move the intensity switch to the desired intensity.
On vehicles with a HI/MED/LO intensity switch,
LO will provide 1/3 of the full braking capacity of
the engine, MED will provide 2/3 of the full brak-
ing capacity, and HI will provide maximum engine
braking. On vehicles with a HI/LO intensity
switch, LO will provide ½ of the full braking ca-
pacity of the engine; HI will provide maximum
engine braking.
4. Use the intensity switch set at the LO position
when driving on flat, open stretches of road. If
the service brakes are still required to slow down
on a grade, switch to a higher setting on the
dash switch until there is no need for the service
brakes. Grade descent speed should be such
Engines
NOTICE
Fig. 7.17. The engine brake will
7.14