Chevrolet 10 Series 1970, Service Manual

Page: 302 / 671

BRAKES 5-64
Disassembly
1. Push down on spring w asher.
2. R em ove key pin.
3. R em ove spring w asher, spring and key.
Cleaning and Inspection of Parts
Wash a ll m etal p arts in cleaning solvent.
If the key o r body is badly scored , the com plete drain
cock should be replaced.
Do not attempt to fit a new key in an old body o r vic e
versa .
Repairs
If slight leakage has been p resen t due to a sligh t s c o r ­
ing of the key o r body, the key should be ground in with a
good grade of #400 grinding compound. B efo re the key is
again put in place, it should be given a light application of
a good grade o f cup g rea se.
Assembly
1. In sert key in body.
2. P la c e spring and sprin g washer o v e r key.
3. Push down on sprin g washer and in sert pin in key.
Installation
Using a wrench on hexagon portion of drain cock, screw
in place.
SAFETY VALVE (Fig. 1 10 )
The safety va lve is usually mounted on the r e s e r v o ir .
The va lve allow s a ir to escape fro m the r e s e r v o ir when
the a ir p ressu re exceeds a predeterm in ed amount.
Removal
Unscrew com plete v a lv e fro m line fitting.
Disassembly
U nscrew the spring cage (fig . 110) fro m the body of the
safety va lve. L ift b all va lve fro m body and rem ove
spring, spring seat, and re le a s e pin fro m spring cage.
Cleaning and Inspection of Parts
Clean a ll parts in cleaning solvent. Examine the ball
va lv e fo r signs o f pitting o r scratch es. If any damage is
evident the safety va lve should be replaced. Clean ball
va lv e seat thoroughly. Check the body and spring cage
fo r cracks. Be sure the exhaust p ort in the spring cage
is not plugged.
Assembly
1. P la c e the b all va lve in the body o f the safety va lve.
2. P la ce spring re le a s e pin and spring seat in spring
cage with the adjusting s c re w assem bly. Position
the spring seat o v e r the b all va lve and s c re w the
spring cage to the body.
Installation
S crew safety va lve in place in p ro p er r e s e r v o ir line.
Tests and Adjustments of Rebuilt Unit
Both operating and leakage tests, indicated under S e rv ­
ic e Check, must be made a fter rebuilding the safety valve
and the va lve must m eet the follow in g sp ecification s:
1. Leakage at the exhaust p ort should not exceed a one-
inch soap bubble in one second.
2. The safety va lve should be set to “ blow o f f ” at ap­
p roxim a tely 150 p si. The p ressu re setting may be
adjusted by loosening the lock nut and turning the
adjusting screw . Turning the adjusting s c re w clo ck ­
w ise, ra is e s the p ressu re setting. Turning the ad­
justing s c re w cou n ter-clock w ise lo w ers the p ressu re
setting. The setting o f the adjusting s c re w should be
locked by lightening the adjusting s c re w lock nut
a fte r each adjustment. An accurate test gauge should
be used when adjusting the p ressu re setting o f the
safety v a lve.
F ig . 106—Rear Brake Parts Id e n tific a tio n
1. A c tu a tin g Cam
2. R o lle r
3. Brake
Shoe F acing
4. Brake Shoe
5. A n c h o r Pin Lock Ring
6. A n c h o r Pin
7. Flange P late
8. Shoe Return S pring
9. R o lle r Pin
SINGLE CHECK VALVE
A check va lv e is provid ed in the line between the r e ­
s e r v o ir and the com p resso r to retain a ir p ressu re in the
event o f co m p resso r o r line fa ilu re .
Removal
1. Exhaust a ir fro m brake system .
2. R em ove a ir lin es at sin gle check v a lv e and rem ove
v a lv e (fig . 112).
Disassembly
U nscrew cap nut fro m body and rem ove grom m et. R e ­
m ove disc v a lve, spring, and va lve stop bushing from
body.
Cleaning and Inspection of Parts
Clean a ll parts in cleaning solvent. Inspect disc va lve
and seat fo r co rro sio n . Inspect body and cap nut fo r
cracks o r damage. If any damage is p resent, replace
en tire va lve assem bly.
Assembly
1. P osition va lve stop bushing, sprin g and disc va lve in
body.
CHEVROLET TRUCK SERVICE MANUAL