Chevrolet 70 Series 1970, Service Manual

Page: 475 / 841

ENGINE COOLING SYSTEM 6K-8
com pletely thawed out. UNDER NO CIRCUM­
STANCES SHOULD ENGINE BE RUN WHEN COOL­
ING SYSTEM IS FROZEN SOLID.
The inhibited y e a r-a ro u n d (perm anent-type)
engine coolant, used to fill the cooling sy stem at
the fa c to ry is a high quality solution that m eets
G eneral M otors Specification 1899-M. T his fac-
to ry -f ill coolant solution is form ulated to w ith­
stand two full calen d ar y e a rs of no rm al operation
without draining o r adding inh ib ito rs, and provides
freez in g p ro tectio n to -2 0 °F .
If is the o w n er's re sp o n sib ility to keep the
fre e z e p ro te c tio n a t a level com m ensurate with
the a r e a in which the vehicle w ill be operated. R e­
g a rd le ss of clim ate, sy stem p ro tectio n should be
m aintained a t le a s t to 0 °F ., to provide adequate
c o rro sio n p ro tectio n . When adding solution due to
lo ss of coolant fo r any re a so n , o r in a r e a s w here
te m p e ra tu re s low er than -2 0 °F ., may o cc u r, a
sufficient am ount of an ethylene glycol b ase cool­
ant that m eets GM Specification 1899-M should be
used.
E very two y e a rs the cooling sy ste m should be
se rv ic e d by flushing with plain w ater, then com ­
pletely refillin g with a fre s h solution of w a te r and
a high-quality, inhibited (perm anent type) glycol
b a se coolant m eeting GM Specification 1899-M,
and providing freez in g protectio n at le a s t to re ad
0 °F . At th is tim e, a lso add GM Cooling System
Inhibitor and S ealer o r equivalent. In addition,
Cooling S ystem Inhibitor and S ealer should be add­
ed every fa ll th e re a fte r. GM Cooling System In­
h ib ito r re ta rd s the form ation of ru s t o r sc a le and
is com patible with alum inum com ponents.
IMPORTANT: Alcohol o r m ethanol b ase cool­
a n ts o r p lain w a te r a r e not recom m ended fo r your
tru c k a t any tim e.
WATER TEMPERATURE INDICATOR
E le c tric type te m p e ra tu re gauge sy ste m con­
s is ts of an engine th e rm a l plug elec trically con­
nected with re g iste rin g gauge mounted on in s tru ­
m ent panel. R efe r to applicable w iring diagram in
"W iring D iagram " booklet. System is activated
when ignition is tu rn ed on.
Engine unit is in stalle d in engine w ater m ani­
fold on V6 gasoline engines (fig. 7) and in th e rm o ­
s ta t housing on 6V-53 d iesel engines (fig. 2).
The engine unit is mounted in engine w a te r
m anifbld on 6-71 D iesel engine (fig. 8), o r in
th e rm o s ta t housing on 8V-71 D iesel engines (fig.
9). Engine w a te r te m p e ra tu re , acting on elem ent
in th e rm a l plug, cau ses variatio n of re s is ta n c e in
e le c tric a l c irc u it.
WATER TEMPERATURE INDICATOR TEST
1. D isconnect w ire a t engine unit.
Figure 8 —Temperature G auge Sending U nit and
Engine O verheat Switch 16-7I Diesel Engine)
2. Connect a te s t light consisting of a 12-volt,
2-candlepow er bulb and a p a ir of te s t leads in c i r ­
cuit by clipping one lead to b attery p o sitive te r m ­
inal and o th er lead to body of engine gauge unit. If
bulb lig hts, unit is p ro p e rly grounded. If bulb does
not light, check fo r p re se n c e of sealing compound
around th rea d s of unit. Rem ove compound and r e ­
peat te s t. Make s u re unit is p ro p e rly grounded
b efo re proceeding with next te st.
3. Remove te s t lead fro m body of unit and
connect lead to te rm in a l of unit. If bulb lig h ts, en­
gine unit is intern ally s h o rt-c irc u ite d and should
be rep laced .
4. Rem ove te s t light and re in s ta ll w ire on
unit.
Figure 9 —Temperature
Gauge
Sending U nit and
Engine O verheat Switch I8V-71 Diesel Engine)
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCKSHOP MANUAL