Chevrolet 10 Series 1970 Service Manual page 298

BRAKES 5-60
4. Hold stop s crew w hile tightening lock nut.
5. Check brake operation
re le a s e .
Control V alv e Removal
1. S cribe o r m ark the con trol va lve and mounting sup­
port in som e fashion so that the va lve can be re a d ily
positioned during installation.
2. Disconnect e le c tr ic a l connector at brake ligh t switch.
D isconnect all a ir lines into and out of control va lve
including exhaust hose. On standard a ir brake sy s­
tem s disconnect lin es enterin g p ressu re protection
valve.
3. R em ove th ree bolts secu rin g va lv e to brake pedal
support. R em ove v a lv e assem bly.
4. Rem ove stop lamp sw itch fro m
standard a ir brake system s rem ove p ressu re p ro ­
tection valve.
Disassembly
1. R em ove stop s c re w (20) fro m body.
2.
R em ove piston assem b ly fro m body. R em ove spring
( 10).
3. R em ove piston snap rin g (2). R em ove sprin g guide
(3), sprin g (6), shim w ashers and cushion (5), and
shim w ashers (9).
4. R em ove piston ' O'
seal (8).
5. S cribe a line on the cap (16), cage (21), and body (1)
fo r r e fe re n c e during assem bly. Rem ove cap screw s
and lockw ashers fro m end cap. Separate end cap (16)
fro m cage (21). R em ove
' O' rin g (14).
6. W hile holding exhaust va lv e (13), rem ove nut (18).
R em ove inlet v a lv e
(13) fro m cage (21).
7. R em ove snap rin g (7) and exhaust port hose fittin g
(4).
Inspection and Cleaning
1. Wash a ll m etal parts in m in eral sp irits o r cleaning
fluid.
2. Scrape old gasket m a te ria l fro m mating su rfaces of
end cap (16) and cage (21).
3. Clean and wipe d ry in let va lve
va lv e (13). They must be rep laced if nicked or
worn.
4. Exam ine inlet v a lv e seat in cage assem bly and ex­
haust v a lv e seat on piston (12). They must be fr e e
o f nicks. Crocus cloth may be used to smooth off
sligh t nicks; if nicks a re too deep, rep la ce piston
o r cage.
Assembly
1. In stall exhaust port hose fittin g (4) and snap rin g (7)
in exhaust port.
2. A ssem b le spring (15) and exhaust va lv e (13) in cage
assem bly. In stall in let va lv e (17) on exhaust va lve
stem . Install and tighten nut (18).
3. In stall new 'O ' rin g (14) and place cage assem bly
into body aligning s c rib e m arks. P la c e a new gasket
(19) on cage. P la c e cap (16) on gasket aligning scrib e
m arks made in Step 5 of the disassem bly procedure.
In stall and tighten cap s c re w s and lock w ashers.
4. In stall new piston 'O ' rin g (11) and V e e -b lo c k seal
(8). P la c e origin al shim s o r 4 s e rv ic e shim s (9) in
piston. P la c e o rig in a l shim s o r 2 s e r v ic e
fo r fu ll application
control va lve. On
rin g sea l (11) and V e e-b lo ck
cage assem bly. R em ove
(17), spring (15) and exhaust
(17) and exhaust
shims
and cushion (5) in piston. P la c e sprin g (6) and spring
and guide (3) in piston. Install snap rin g (2).
5. Apply a light lubricant to inside b ores of body. P la c e
spring (10) in body. In stall piston assem bly in body.
6. Push piston down and in stall s crew (20) with head of
sc rew tight against body.
NOTE: The gap between the exhaust va lve and
seat must be
checked by inserting a fe e le r gauge through a
d e liv e r y port.
Testing V a lv e
Released Position
Plu g a ll cylin der ports.
gauge to inlet port. Check exhaust port with soapy w ater.
No leakage allowed.
Applied Position
W ith a ir supply and gauge connected to in let port, install
an a ir gauge in cylin der d e liv e ry port. D epress piston to
allow 5 to 10 psi a ir pressu re to r e g is te r on gauge in
cylin d er port. Check exhaust port with soapy water; a
one-inch soap bubble in th ree seconds p erm iss ib le.
D epress piston slo w ly and note that cylin d er p ressu re
on gauge builds up in proportion to p ressu re indicated on
gauge at inlet port.
gauges should read alike;
seconds is p erm issib le at exhaust port.
Control V alv e Installation
1. In stall va lve by re v e rs in g rem o va l steps.
2. S ecu rely tighten a ll a ir lines and brake light switch.
3. Build up p ressu re in system to at lea st 100 psi.
Check a ll connections with pedal in fu lly relea sed
and fu lly applied positions with a soapy w ater solu­
tion. No leakage is p erm issib le.
QUICK RELEASE VALVE (Fig. 1 03)
The quick re le a s e va lve is a diaphragm operated valve
that is installed between the brake con trol va lve and the
brake cham bers. One is used with the front cham bers and
one with the re a r cham bers.
The re lea se va lve functions to speed up the brake r e ­
lea se tim e by reducing the distance the a ir p ressu re must
tra v e l to the point o f rele a s e.
Removal
1. Disconnect a ir lin es at quick re le a s e va lve.
2. Rem ove mounting bolts and rem ove va lve.
Disassembly
Rem ove a ll d irt and grea se fro m e x te r io r o f va lve,
using cleaning solvent and a brush. Inspect e x te rio r of
v a lv e fo r broken o r damaged parts.
aged parts must be replaced.
U nscrew co ver, lift out diaphragm spring, diaphragm
spring seat and diaphragm.
Cleaning and Inspection of Parts
Wash a ll m etal parts in cleaning solvent.
Diaphragm : Examine diaphragm fo r signs o f cracking,
w ea r o r damage. C a refu lly examine the lo w er face o f the
diaphragm which contacts the p ort seat in the co v e r fo r
signs o f pitting o r grooving.
o f these conditions are found.
f
.06" minimum. This may be
Connect a ir supply and a ir
W ith piston fu lly d epressed both
a one-inch bubble in three
A ll broken o r dam­
Replace diaphragm if any
CHEVROLET TRUCK SERVICE MANUAL