Chevrolet 10 Series 1970, Service Manual

Page: 309 / 671

BRAKES 5-71
OPERATION TEST AND LEAKAGE TESTS
H A N D CONTROL VALVE
O p e ratin g Tests
1. Check the d e liv e ry p re s s u re o f the v a lve, using an
accurate test gauge connected to the t r a ile r brake
s e r v ic e line at the back o f the cab. With a ir system
fu lly charged, and with va lv e operating handle in
fu lly applied position, test gauge should show the
sam e p ressu re (within 5 pounds) as r e g is te re d on the
dash a ir gauge.
2. M ove the handle to s e v e ra l positions between fu lly
re le a s e d and fu lly applied and note that p ressu re
re g is te r e d on the test gauge v a r ie s in accordance
with the position o f the handle.
Leakage Tests
1. Coat the exhaust p o rt with soap suds with operating
handle in fu lly re le a s e d position to check fo r leakage.
Leakage in excess o f a 1-inch bubble in one second
is not p e rm is s ib le . Leakage evidence by this test is
probably caused by a w orn o r d e terio ra ted inlet va lve
sea l, o r binding o r c o rro s io n between the va lv e s and
v a lv e guides in va lve cage, preven tin g the inlet va lve
fro m fu lly closin g.
2. W ith operating le v e r in fu lly applied position coat
exhaust p ort with soap suds. Leakage evidenced by
this test may be due to a worn o r d eterio ra ted e x ­
haust va lv e seal o r by leaking piston seals.
DOUBLE CHECK VALVE
O p eratin g Tests
1. Apply truck brakes and note that the brakes apply
prom p tly on both the truck and the tr a ile r . R elea se
truck brakes and note that brakes on truck and
t r a ile r both re le a s e prom ptly.
2. M ove hand control va lve le v e r to applied position
and note that brakes apply only on the tr a ile r . M ove
con trol va lve le v e r to relea sed position and note that
tr a ile r brakes re le a s e prom ptly.
Leakage Tests
1. Apply truck brakes and check fo r leakage at hand
control va lve exhaust port, using soap suds.
2. Apply t r a ile r brakes only with hand control va lve
and check fo r leakage at truck brake application
va lve exhaust p ort, using soap suds.
3. Leakage o f a one inch bubble in one second is p e r ­
m issib le in eith er o f these tests. If leakage exceeds
this sp ecification , rep la ce the shuttle v a lve.
PUSH PULL VALVE
O p eratin g Tests
1. P u ll out em ergen cy a ir va lve knob to exhaust a ir
pressu re fro m va lv e control line. Disconnect t r a ile r
em ergen cy lin e fro m em ergen cy outlet p o rt at va lve
BRAKE CHAMBER
-BRAKE CHAMBER DRAIN COCK
PP 3 CONTROL VALVE
(WITH MANUAL CONTROL)
BRAKE CHAMBER
DRAIN COCK
TRAILER HOSE-
EMERGENCY
TRAILER HOSE-
SERVICE P“5U
-SERVICE LINE SHUT-OFF
VALVE
DOUBLE CHECK VALVE /
QUICK RELEASE
—! ))
VALVE
-BRAKE CHAMBER
F ig . 120—A ir Brake System —T ra iIe r
CHEVROLET TRUCK SERVICE MANUAL