AIR CHAMBER AND MASTER CYLINDER
1. Stroke indicator.
2. Master cylinder.
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 primary cup has become
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 SERVICING
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 brake
CAUTION: Do not use mineral base cleaning solvent
tetrachloride, acetone, paint thinner, etc. These
solvents will damage rubber parts and cause them to
become soft and of no use.
AIR REMOVAL FROM BRAKES
(Bleeding the Brakes)
VALVES THAT LET THE AIR OUT