User guide

Section I - Trouble Shooting & Guidelines • Page 6
TROUBLE SHOOTING POWER BRAKES
BASIC TEST
ENGINE OFF. Depress and release brake pedal several
times to remove vacuum from power section.
Depress pedal and hold with light pressure, 15 to 25 lbs.,
and START ENGINE.
If power section is operating, pedal will fall slightly and
then hold. Less pressure will be needed to hold pedal down.
IF POWER IS NOT OPERATING - disconnect
vacuum hose from power section vacuum valve.
Then, with ENGINE RUNNING, check vacuum
supply with a vacuum gauge. There should be at
least 14 inches of vacuum.
IF POWER SECTION IS OPERATING - do the
following VACUUM LEAK TEST.
VACUUM LEAK TEST
IF VACUUM SUPPLY IS
BELOW 14 INCHES -
replace or repair vacuum
hose and vacuum
fittings.
IF VACUUM SUPPLY IS
14 INCHES OR MORE -
power section is defec-
tive and should be
replaced.
When adequate vacuum
supply is obtained, repeat
BASIC TEST.
HYDRAULIC LEAK TEST
IF APPLICATIONS ARE POWER ASSISTED -
there is no vacuum leak. Do the following
HYDRAULIC LEAK TEST.
IF APPLICATIONS ARE NOT POWER AS-
SISTED - disconnect vacuum hose from intake
manifold or power section check valve, whichever
is easier. If disconnected at check valve, attach a
short length of hose to valve.
Blow into hose attached to check valve. If air
passes through, valve is defective.
IF CHECK VALVE IS
DEFECTIVE - install new
check valve and repeat
the VACUUM LEAK
TEST.
IF CHECK VALVE IS
OKAY - power section is
leaking and should be
replaced.
Depress and release brake pedal several times.
Then hold pedal depressed with medium pres-
sure, 25 to 30 lbs.
IF PEDAL FALLS AWAY - hydraulic system is leaking.
Check for external leakage at wheel cylinders, hy-
draulic line and hoses. If there is no external leak,
there may be an internal leak (master cylinder cups.)
Repair or replace parts needed to correct leak.
IF PEDAL DOES NOT FALL AWAY
- hydraulic system is not leaking.
Run engine to medium speed. Release accelera-
tor and turn ENGINE OFF. This builds up vacuum.
Wait 90 seconds and apply brakes. Two or more
applications should be power assisted.
SECTION I - TROUBLE SHOOTING & GUIDELINES