Kenworth T410, Driver'S Handbook Manual

Page: 266 / 418

Page 240 CAT: 8612 November 2019
PREVENTIVE MAINTENANCE
AIR GAUGES AND AIR LEAKS
Your Kenworth comes with two separate air pressure gauges for two
separate systems, Primary and Secondary. The Primary gauge indicates
pressure in the rear braking system, the Secondary gauge indicates
pressure in the front braking system. Each gauge indicates the amount
of air pressure in kilopascals (kPa).
Do not operate the vehicle if a leak in the air system is detected.
Conduct the following procedure and contact an authorised Kenworth
dealer (or any other properly equipped service centre) if a leak is
detected. Failure to check the brakes or follow these procedures
could cause a system failure, increasing the risk of an accident.
If the light and alarm do not turn off at start-up, do not try to drive the
vehicle until the problem is found and fixed. If the pressure in either or
both systems is too low for normal brake operation, (i.e. the pointer of one
gauge falls below 414kPa (60psi)), a warning light on the gauge will glow
and the audible alarm will sound.
Follow the procedure below to check the compressed air system for leaks,
periodically or after maintenance or replacement of air system components:
1. Build up air pressure in the system to the governor cut out point or
until 827kPa (120psi) is reached.
2. Stop the engine and release the service brakes.
3. Without applying the brake pedal, observe the rate of air pressure
drop. This rate should not exceed 14kPa (2psi) per minute.
4. Start the engine and build up the air pressure again.
5. Stop the engine and apply the brakes fully. Apply the brake pedal
and hold it down for five minutes. The pressure drop should not
exceed 21kPa (3psi) per minute.
6. If you detect excessive leakage (air pressure loss greater than 21kPa
(3psi) after five minutes of brake application), a leakage test should
be made at the air line connections and at all air brake control units.
These tests should determine where air is escaping.