Group 170
Preventive Maintenance
Check Engine Controls and Performance
Note: For further information refer to literature in Func-
tion Group 3.
Check engine controls and performance while moving
through the gears. Accelerator pedal should work
smoothly and without any hesitation in engine response.
Engine should accelerate smoothly and without hesita-
tion, misses or surges. Also check the exhaust through
the mirrors for excessive smoke during acceleration.
During acceleration in a low gear, let engine go to full
speed on a flat stretch of road. Note maximum engine
speed. Check each engine manufacturer’s specifications
for correct speed.
Check Engine Brakes
Note: For further information refer to literature in Func-
tion Group 3.
When operating a tractor bobtail without a trailer or on
slippery roads, the engine brake switch must be in the
“OFF” position. Failure to follow these instructions can
result in loss of vehicle control and serious personal
injury or death.
If the engine is equipped with an exhaust brake (only on
Volvo) or an engine brake, check the effectiveness of the
retarding force when the brake is engaged.
Engine Brake (D12)
The engine brake has two operation modes, high and
low, that are selected by one or two switches on the
dashboard. Make sure the brake function disengages by:
• Either depressing accelerator or clutch pedal.
• Engine speed goes under 1000 rpm (1000 r/min).
• Vehicle speed goes under 2 mph (3 km/h).
• Turbo boost pressure going over 50 kPa (7 psi)
• Engaging PTO.
• Engaging ABS.
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