Master Cylinder/Power Booster; Power Booster Vacuum Test; Power Booster Check Valve Test; Metering Valve - Jeep Wrangler 1997 Manual

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DIAGNOSIS AND TESTIN
MASTER CYLINDER/POWER BO
(1)
Start engine and check b
connections. A hissing noise find
Correct any vacuum leak before
(2) Stop engine and shift tra
tral .
(3) Pump brake pedal until al
booster is depleted .
(4) Press and hold brake pe
pressure . The pedal should hol
falls away master cylinder is f
age) .
(5) Start engine and note pe
falls away slightly under light
holds firm. If no pedal action i
booster, vacuum supply, or vac
faulty. Proceed to the POWER
TEST .
(6) If the POWER BOOSTE
passes, rebuild booster vacuum
Release brake pedal. Increase e
rpm, close the throttle and imm
ignition to stop engine .
(7) Wait a minimum of 90 se
action again. Booster should provide two or more vac-
uum assisted pedal applications . ] If vacuum assist is
not provided, booster is faulty.
I
STER
oster vacuum hose
cates vacuum leak .
roceeding.
smission into Neu-
al under light foot
firm, if the pedal
ulty (internal leak-
al action it should
foot pressure then
discernible, power
um check valve is
OOSTER VACUUM
VACUUM TEST
reserve as follows:
gine speed to 1500
diately stop turn off
POWER BOOSTER VACUUM EST
(1)
Connect vacuum gauge to booster check valve
with short length of hose and T- fitting (Fig . 8).
(2) Start and run engine at c rb idle speed for one
minute.
(3) Observe the vacuum supply. If vacuum supply
is not adequate, repair vacuum
supply.
(4)
Clamp hose shut between,' vacuum source and
check valve.
(5) Stop engine and observe v cuum gauge.
(6) If vacuum drops more th,~,In one inch HG (33
millibars) within 15 seconds, booster diaphragm or
check valve is faulty .
POWER BOOSTER CHECK "LVE TEST
(1)
Disconnect vacuum hose from check valve.
(2) Remove check valve and valve seal from
booster.
(3) Use a hand operated vacuum pump for test.
(4) Apply 15-20 inches vacuum at large end of
check valve (Fig . 9).
(5) Vacuum should hold steady. If gauge on pump
indicates vacuum loss, check 'valve is faulty and
should be replaced .
VACUUM
GAUGE
SHORT
CONNECTING CHECK
HOSE
VALVE
BOOSTER
CHECK VALVE
APPLY TEST
VACUUM HERE
VALVE
SEAL
COMBINATION VALVE
BRAKES 5-9
INTAKE
MANIFOLD
Fig. 8 Typical Booster Vacuum Test Connections
Fig. 9 Vacuum Check Valve And Seal
J9oos-81
8031e866
Metering Valve
Metering valve operation can be checked visually
and with the aid of a helper. Observe the metering
valve stem while a helper applies and releases the
brakes . If the valve is operating correctly, the stem
will extend slightly when the brakes are applied and
retract when the brakes are released . If the valve is
faulty, replace the entire combination valve as an
assembly.
Pressure Differential Switch
(1)
Have helper sit in drivers seat to apply brake
pedal and observe red brake warning light.
(2) Raise vehicle on hoist.