Chevrolet 10 Series 1970 Service Manual page 295

rele a s in g braking p ressu re d ire c tly to the atm osphere.
Removal
1. B lock o r hold v e h icle by a means other than a ir
brakes.
2. Open drain cocks and exhaust a ir p ressu re fro m a ir
brake system .
3. Disconnect a ir lines fro m re la y va lve.
4. R em ove mounting bolts and rem ove r e la y valve.
Disassembly
1. R em ove c o v e r, diaphragm, diaphragm ring, b leed er
passage grom m et, and b le e d e r passage filt e r .
The re la y v a lv e is tested each tim e the tra c to r brakes
a re applied and relea sed . Should s e rv ic in g be indicated,
such as leakage, tim e lag, etc., it can be accom plished
quickly and easily.
The r e la y -in le t va lve
there is leakage at the exhaust port. M e re ly rem o ve the
T ru a rc retaining ring and the sh ield at the exhaust port,
an on -th e-veh icle s e rv ic e .
hold the parts assem bled;
gradu ally fo r c e the parts out.
If v a lv e reaction tim e is
r e la y piston can be rem oved by separating the va lve
housing and housing c o ver.
Should operation of the va lve becom e slow o r hesitant,
a fte r prolonged s e r v ic e ,
maintenance to dism antle and clean the unit. When r e ­
assem blin g the va lv e it
rubber parts. Then c o v e r b earin g su rfaces of the a ir
section with a thin film o f grea se.
k it is recom m ended, as
n ecessary fo r com plete re-conditionin g.
Installation
1. Clean o r rep lace lines to r e la y v a lve.
2. Mount rela y va lve secu rely.
3. Connect a ir lines.
AIR BRAKE CHAMBERS (Figs. 9 8 and 9 9 )
An a ir brake cham ber is used to con vert the energy of
com p ressed a ir into the m echanical fo rc e and motion r e ­
quired to apply the brakes. The yoke on the brake cham­
b e r push rod connects
mounted on the brake cam shaft.
As a ir p ressu re enters the brake cham ber behind the
diaphragm , the diaphragm fo r c e s the push rod outward,
applying fo rc e to the slack adjuster which rotates the
brake cam shaft and applies the brakes.
a ir p ressu re the brake shoe return springs and the push
rod spring return brake shoes, cam shaft, slack adjuster,
push rod and diaphragm to the re le a s e d position.
Leakage Test
With a fu ll p ressu re application, check the brake cham­
b e r fo r leakage. No leakage is p erm is s ib le .
If leakage is detected around the flange, or clam ping
ring, the bolts should be tightened even ly but only enough
to stop the leakage otherw ise the diaphragm , flange se a l­
in g su rface o r clamping rin g could be distorted.
Removal
1. Disconnect a ir line and push rod yoke.
2. R em ove brake cham ber.
can be pulled and rep laced i f
Guide s e a l fr ic tio n tends to
how ever, the spring w ill
slow or s e v e re acting, the
it would be good p reven tive
is advisable to rep lace a ll
The use of a re p a ir
it contains a ll of the parts
to a slack adjuster which is
Upon re lea se of
Installation
1. Mount brake chamber to mounting bracket.
2. If p ossible, push rod should point down to obtain
maximum drainage.
3. In stall yoke and its nut on push rod and connect to
slack adjuster.
Check the angle fo rm e d by the push rod and slack
4 .
adjuster. The angle should n ever be le s s than 90°
when fu ll a ir p ressu re is applied to the brake cham­
b er when the brakes a re cold and p ro p e rly adjusted.
Disassembly
1. A fte r cleaning the e x te r io r of the brake chamber,
m ark it in such a way that it can be assem bled the
sam e way. If the brake cham ber is to be dism antled
on the veh icle, fo r exam ple to change the diaphragm
o r spring, fir s t back off the slack adju ster to r e lie v e
the return spring p ressu re against the p ressu re
plate, then fo llo w d isassem b ly procedu re below.
2. P u ll out push rod and clam p it at the non-pressu re
plate with v is e o r v is e grip p lie rs . If n ecessary, use
a ir p ressu re to m ove the push rod out. G rips o f
v is e o r v is e grip p lie r s should be c o v e re d o r taped
to preven t damage to push rod.
3. R em ove clam p rin g nuts and bolts.
Spread clam p rin g sligh tly, just enough to slip it off
4 .
the plates. It is som etim es n ecessa ry to use a
s cre w d r iv e r and gradually p ry under the clam p rin g
to rem ove it. If the clam p ring is to be reused, cau­
tion should be taken against bending it out of shape.
5„ Rem ove p ressu re plate and diaphragm.
6. Rem ove yoke and lock nut fro m push rod.
7. R elea se grip on push rod.
8. Rem ove push rod assem bly, spring and other details.
Cleaning and Inspection
Clean a ll m etal p arts and inspect them fo r damage.
Dam aged parts should be replaced. If it is n ecessa ry to
rep la ce the return spring, be sure the c o r r e c t rep la ce ­
ment spring is used. Inspect diaphragm and any other
rubber parts fo r w ea r o r deterioration and rep lace i f
necessary.
Assembly
1. Stand push rod assem bly upright on a fla t su rface.
2. P osition return sprin g and n on-pressu re plate on
push rod.
3. P r e s s the n on-p ressu re plate down against the ten­
sion of the sprin g until the plate bottom s on the fla t
surface.
Now clam p the push rod at the n on-pressu re plate in
4 .
a v is e o r with v is e grip p lie r s whose grip s have been
taped o r covered.
5. W ith the push rod held in this manner, place the
clamp rin g o v e r the clam ping su rface of the non­
p ressu re plate.
6. P osition diaphragm in pressu re plate and joint the
two with the non -pressu re plate by w orking the clamp
rin g o v e r the clam ping surface of the p ressu re plate
with the use of v is e grip p lie rs o r lik e tool drawing
the clamp lugs together.
7. A ssem b le bolt and nut in clamp. It is som etim es
n ecessa ry to tap the clam ping ring to center it, and
this should be done only with a soft faced m allet.
8. R elea se hold on push rod and in sta ll rem aining clamp
rin g nut and bolt.
BRAKES 5-57
CHEVROLET TRUCK SERVICE MANUAL