Chevrolet DB90 Series, Руководство по обслуживанию

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S ec. 6A-54
GASOLINE ENGINES
REMOVE INSULATOR
AIR HOSE
BUSHING
(As req'd)
3 / 8 " PIPE
THREAD
SPARK PLUG BODY
T -8132
Figure 2 —A ir Su p ply A da p ter Tool
and at every 12-m onth or 12,000 m ile interval
th erea fter. A te ste r (AC Type CT-3) is available
for u se in checking the condition of the cran k case
ventilation sy ste m . F ollow the in stru ction s furn­
ish e d with the te s te r when making sy ste m check.
The C T -3 T e ste r functions a s a p r e ssu r e and
or vacuum gauge. Changes in either the p r e ssu r e
or vacuum w ill m ove a colored view ing drum up­
w ard or downward in relation to fixed window open­
in g s. A s e le c to r knob on the bottom of te s te r , with
settin g s "A" through "O" p erm its te ste r calibration
to match air flow through v a lv e s. With the C T -3
properly connected to an idling engine, a sin g le
color or a combination of co lo rs of red, green or
orange v isib le in the window openings, indicates
the operating condition of the P o sitiv e C rankcase
Ventilation S ystem . Window reading interpretations,
probable trou b les, and rem ed ies a re fully covered
in the PCV D iagn osis Chart (fig. 1).
B rief in stru ction s for using the C T -3 te ste r
a r e as follow s:
1. In stall the dipstick tube plug provided in
the te s te r kit.
2. Set parking brake, sta rt engine, and allow
to id le.
3. R em ove the breather connection from the
a ir clean er and p la ce the PCV te ste r connection
at the opening to the crankcase (rocker arm cover).
The PCV te ste r should be se t to the "M" position
fo r V6 engine, or to "K" p osition on V8 engines.
4. A green reading in d icates the sy ste m is
operating sa tisfa c to r ily and no further testin g is
required. An orange or red reading indicates in­
su fficien t a ir flow in the ventilation lin e . Addition­
a l testin g is required to determ ine the ca u se.
5. Rem ove rocker arm c o v ers and inspect
the cran k case ventilation va lv es which a re screw ed
into threaded p orts in cylin d er heads.
NOTE: One valve is used in each cylinder
head on V6 en gines, and two v a lv e s are used in
each cylinder head on V8 engines.
U se sock et w rench to rem ove crankcase vent­
ilation v a lv es in c a se the testin g in d icates a m al­
function in cran k case ventilation sy ste m .
Clean v a lv es, h o se s, and breather a ssem b ly ,
then in sta ll p a rts and repeat the te s t a s previou sly
d escrib ed .
If, after ventilation v a lv e s an d /o r h o ses and
other sy ste m com ponents a r e in sta lled , the te st
in d icates u n satisfactory p erform an ce of the vent­
ilation sy ste m , a check should be made to s e e that
crankcase openings w ere a ll com pletely sea led
during te st.
It may be n e c e ssa r y to make r e p a irs to engine
com ponents such a s v a lv es, piston rin g s, or oil
s e a ls to make p o ssib le a sa tisfa c to ry operating
crankcase ventilation sy stem .
VALVE SPRING REPLACEMENT
(V6 AND V8 CYLINDER HEAD)
In m ost v e h ic le s it is p o ssib le to rep lace a
broken or d efective valve spring without rem oving
cylin d er head from engine. F igure 2 show s how to
make an air h ose adapter from a d iscarded spark
plug to be u sed to connect air lin e to cylinder at
which the valve spring is to be replaced. Adapter
is made from spark plug by cutting off electrod e
and the upper portion of plug body a s shown. R e­
m ove insulator from body, then thread the body
upper cavity with 3 /8 -in c h pipe tap. In stall bush­
ing and fittin gs as n e c e ssa r y to connect a ir h ose.
U se sam e procedure a s d escrib ed in S erv ice
Manuals ST 135-70 and ST 332-71 to rep lace valve
sp rin gs an d /or valve stem o il s e a ls .
CRANKSHAFT PULLEY AND
HUB REPLACEMENT
NOTE: 401M engines do not u se a crankshaft
dam per.
CRANKSHAFT PULLEY
AND/OR HUB REMOVAL
1. Rem ove radiator if n e c e ssa r y , to provide
a c c e s s to crankshaft p u lley. On engines w ith fan
blades in sta lled on crankshaft p u lley, rem ove fan
blad es from crankshaft pulley hub. A lso rem ove
a c c e s s o r y d rive b elts.
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT