BRAKES 5-9
DIAGNOSTICS
ROAD TESTING BRAKES
Brakes should be tested on dry, clean, smooth and reasonably
level readway which is not crowned. Road test brakes by making
brake applications with both light and heavy pedal forces at various
speeds to determine if the vehicle stops evenly and effectively.
Also drive vehicle to see if it leads to one side or the otherwithout
brake application. If it does, check the tire pressure, front end
alignment and front suspension attachments for looseness. See
diagnosis table for other causes (5-10).
BRAKE FLUID LEAKS
Check the master cylinder fluid levels. While a slight drop in
reservoir level does result from normal lining wear, an abnormally
low level indicates a leak in the system. In such a case, check
the entire brake system for leakage. If even a slight evidence of
leakage is noted, the cause should be corrected or defective
parts should be replaced.
If fluid level is lower than the minimum level of reservoir, refilling
is necessary. Fill reservoir with specified brake fluid.
SUBSTANDARD OR CONTAMINATED BRAKE
FLUID
Improper brake fluid, mineral oil or water in the fluid may cause
the brake fluid to boil or the rubber components in the hydraulic
system to deteriorate.
If primary piston cups are swollen, then rubber parts have
deteriorated. This deterioration may also be evidenced by swollen
wheel cylinder piston cups on the drum brake wheels.
If deterioration of rubber is evident, desassemble all hydraulic
parts and wash with alcohol. Dry these parts with compressed
air before assembly to keep alcohol out of the system. Replace
all rubber parts in thesystem, including hoses. Also, when working
on the brake mechanisms, check for fluid on the linnings. If
excessive fluid is found, replace the linings.
If master cylinder piston seals are satisfactory, check for leakage
or excessive heat conditions. If condition is not found, drain fluid,
flush with brake fluid, refill and bleed the system.
The system must be flushed if there is any doubt as to the
grade of fluid in the system or if fluid has been used which
contained parts that have been subjected to contaminated fluid.
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