Chevrolet 10 Series 1970, Service Manual

Page: 294 / 671

BRAKES 5-56
codes req u ire gauge accu racy within 10 percent. lined under S e rv ic e Operations in this section.
AIR BRAKE ADJUSTMENTS
PRESSURE PROTECTION VALVE
A ir brake adjustments a re d escrib ed under S ervice
P re s s u re p rotection va lve s e r v ic e p rocedu res a re out- O perations in this section.
SERVICE OPERATIONS
AIR COMPRESSOR
The c o m p resso rs c o vered in this manual are sin g le -
acting tw o -cy lin d er recip ro ca tin g type. The rated capa­
city of the co m p resso r is its piston displacem ent in cubic
fe e t p er minute when operated at 1250 rpm. C om p ressors
can be identified by r e fe r r in g to the name plate attached
to the cylin d er block.
The capacity o f T U -F L O 400 is 7 1/4 cubic fe e t p er
minute. The capacity of T U -F L O 500 is 12 cubic fe e t p er
minute. Both c o m p resso rs are lubricated by the engine
lu brication system .
Removal
These instructions a re gen eral and in som e cases ad­
ditional precautions must be taken.
1. D rain a ir brake system .
2. If w ater cooled type com p ressor, drain engine co o l­
ing system , c o m p resso r cylin d er head and block.
3. D isconnect a ll a ir lines, w ater and o il lin es to and
fro m com p ressor.
4. R em ove co m p re s s o r mounting bolts and com p resso r
fro m engine.
5. Use a g e a r-p u lle r to rem o ve the gea r o r pu lley fro m
c o m p ressor crankshaft.
Installation (Cleaning and Inspection)
1. Clean o il supply line. B e fo re connecting this line to
the co m p resso r run the engine b r ie fly to be sure o il
is flow in g fr e e ly through the supply line.
2. Clean the o il return line o r return passages through
the brackets; these passages must be u n restricted so
o il can return to the engine.
3. P re lu b ric a te c o m p resso r cylin d er w alls and bearings
with clean engine o il b e fo re assem bling com p ressor.
4. A lw ays use a new mounting gasket and be sure o il
hole in gasket and co m p resso r is p ro p e rly aligned
with o il supply line.
5. Inspect pu lley o r gea r and associated parts fo r w ear
o r damage. They must be a neat fit on com p resso r
crankshaft.
R eplace p u l l e y o r gea r i f w orn or
damaged.
6. In stall pulley o r g e a r on com p resso r crankshaft
making sure it p ro p e rly contacts the shaft and does
not ride the key. Tighten crankshaft nut secu rely
and in stall co tter pin.
7. Be sure the a ir clea n er is clean and p ro p e rly in­
stalled. If the c o m p resso r intake is connected to
eith er the engine a ir clean er o r su p erch arger, these
connections must be tight with no leakage.
8. Clean o r rep lace any damage o r d irty a ir o r w ater
lin es which may be corrod ed , b efo re connecting them
to the com p resso r.
U se a new discharge fitting
gasket.
9. A lign co m p resso r d riv e and adjust p ro p er belt
tension.
10. Tighten mounting bolts secu rely and evenly.
11. A fte r installation run co m p resso r and check fo r a ir,
oil, o r w ater leaks at c o m p resso r connections. A ls o
check fo r noisy operation.
RELAY VALVE (Fig. 9 7 )
The a ir brake rela y, quick r e le a s e va lv e is connected
d ire c tly to the rem ote pow er cylin d ers o r the brake
cham bers of a tra c to r (usually at the re a r w heels) to
help speed brake application and re le a s e . The v a lv e is
connected to the application a ir line fro m the application
va lve, and to an a ir line fro m a close-cou p led a u xiliary
r e s e r v o ir . The au xilia ry r e s e r v o ir is d ire c tly connected
by an a ir line to the main r e s e r v o ir and is always charged
with r e s e r v o ir p ressu re.
H O W THE VALVE WORKS
Until the brake application cycle starts, the re la y -
in let va lve is closed and the exhaust va lv e is open to
the atm osphere. When brakes a re applied, the m etered
a ir p ressu re fro m the brake application va lve fo rc e s
the re la y piston down, closin g the exhaust port. Further
m ovem ent of the piston opens the in let va lve, allow ing
a ir p ressu re fro m the a u xiliary r e s e r v o ir to enter the
v a lv e , pass through the d e liv e ry ports, and on to the
brake application lines. A s braking p ressu re underneath
the piston equals controllin g p ressu re above, the piston
balances and allow s the inlet va lv e return spring to
close the in let exhaust va lve. When brakes a re r e ­
leased, the drop in con trollin g p ressu re unbalances the
re la y piston and perm its the exhaust p ort to open, thus
F ig . 9 9 —A ir Brake C ham ber In s ta lle d
CHEVROLET TRUCK SERVICE MANUAL