BRAKE SYSTEM TEST
Check of Operation
The stroke indicator (1) will give an indication when
brake repair is needed. With the brake pedal pushed
down, make note of the stroke of the rod (1) on each
master cylinder. Brake repair is needed when, the
stroke indicator moves more than 1.00 in. (25.4 mm)
from the air chamber of the master cylinder.
1. Stroke indicator.
Start the diesel engine and let the air pressure in
the reservoir go up to cutout pressure.
Push the brake pedal down and keep it in that
Look at the stroke indicator.
Slow movement of the stroke indicator after
it has stopped once, is an indication that
there is leakage in the hydraulic section of
the brake system or that the cup is cut.
Extra travel of the stroke indicator (with
brake linings in contact with discs) is an
indication that air is in the hydraulic section
of the system.
Release the brake pedal.
if either one or both of the stroke indicators
do not retract, this is an indication that a
bypass opening in one of the master
cylinders is closed by dirt, corrosion or the
NOTE: A primary cup which has become too large is an
indication of wrong or dirty hydraulic fluid in the system. If
hydraulic fluid is dirty, remove and repair all components
in the hydraulic system of the brakes. Flush the brake
lines with clean hydraulic fluid.
Check for Leakage
Push brake pedal down and keep it in that
Put soap suds on the connections of the air lines
at the master cylinders and check for air
Release the pedal.
Put soap suds on the exhaust openings of the
control valve for the brakes.
When the pedal is pushed down, leakage must
not be more than a 1.00 in. (25.4 mm) soap
bubble in one minute.
Repair any air leaks that are found.
HYDRAULIC BRAKE SYSTEM
Use heavy duty hydraulic brake fluids meeting
SAE J1703C specifications only. Other fluids may cause
damage to rubber parts.
Do not let dirt or other material get in the brake
fluid when the hydraulic brake system is serviced. Most
parts cleaners may be used to clean master cylinders
and wheel cylinders if the parts are then thoroughly
washed with denatured alcohol or brake fluid to remove
all of the solvent. After removal of the solvent, dry parts
and protect from dust until cylinders are reassembled.
Wash the rubber parts in clean denatured alcohol or
Do not use mineral base cleaning solvent such as
gasoline, kerosene, distillant, carbon tetrachloride,
acetone, paint thinner, etc. These solvents will
damage rubber parts and cause them to become soft
and of no use.