Chevrolet 10 Series 1970 Service Manual page 294

BRAKES 5-56
codes req u ire gauge accuracy within 10 percent.
PRESSURE PROTECTION VALVE
P re s s u re p rotection va lve s e r v ic e p rocedu res a re out-
AIR COMPRESSOR
The c o m p resso rs c o vered in this manual are sin g le -
acting tw o -cylin d er recip roca tin g type.
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 et p er
minute. Both c o m p ressors are lubricated by the engine
lu brication system .
Removal
These instructions are 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 lines 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 or pulley from
co m p ressor crankshaft.
Installation (Cleaning and Inspection)
1. Clean o il supply line.
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 ressor cylin d er w alls and bearings
with clean engine o il b e fo re assem bling com p ressor.
4. Alw ays use a new mounting gasket and be sure o il
hole in gasket and com p ressor is p ro p e rly aligned
with o il supply line.
5. Inspect pulley o r gea r and associated parts fo r w ear
o r damage. They must be a neat fit on com p ressor
crankshaft. R eplace p u l l e y
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.
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 or su p erch arger, these
connections must be tight with no leakage.
8. Clean o r rep lace any damage or d irty a ir o r w ater
lin es which may be corrod ed , b efore connecting them
to the com p ressor.
gasket.
9. A lign co m p ressor
tension.
SERVICE OPERATIONS
The rated capa­
B e fo re connecting this line to
o r gea r i f w orn or
Tighten crankshaft nut secu rely
U se a new discharge fitting
d riv e and adjust p ro p er
lined under S e rvic e Operations in this section.
AIR BRAKE ADJUSTMENTS
A ir brake adjustments a re d escrib ed under S ervice
O perations in this section.
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 co 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 lve is connected
d ire c tly to the rem ote pow er cylin d ers o r the brake
cham bers of a tra cto r (usually at the re a r w heels) to
help speed brake application and rele a s e.
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 lve is open to
the atm osphere. When brakes a re applied, the m etered
a ir p ressu re fro m
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 lve , pass through the d e liv e ry ports,
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 lve
close the in let exhaust va lve.
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
belt
F ig . 9 9 —A ir Brake C ham ber In s ta lle d
The va lve is
the brake application va lve fo rc e s
and on to the
return spring to
When brakes a re
CHEVROLET TRUCK SERVICE MANUAL
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