Chevrolet CHEVY VAN G10 SERIES Service Manual page 171

ENG INE COOLING 6K-2
Water pum p com ponents are n o t serviced separately; th e re­
fore, in th e event o f w ater p um p failure, it will be necessary to
replace th e com plete assembly — removal and installation
Coolant Level
The radiator co olan t level should only be checked w hen the
engine is cool, particularly on trucks equipped w ith air
conditioning. I f th e rad iato r cap is rem oved from a h o t cooling
system , serious personal injury m ay result.
The cooling system fluid level in dow nflow radiator should
be m aintained one inch b elow the b o tto m o f the filler neck o f
the rad iato r w hen cooling system is cold. Coolant level in
crossflow radiators should be m aintained three inches below
the b o tto m o f the filler neck w hen the system is cold to allow
for expansion w hen the coolant is heated. (N ote coolant level
arrow on rear o f rad iato r o u tlet ta n k .) It is very im p o rtan t th a t
th e correct fluid level be m aintained. Overfilling will result in
loss o f coolant as th e co o lan t expands while underfilling (low
level) will result in reduced cooling perform ance.
All tru ck cooling system s are pressurized w ith a 15 lb.
pressure cap w hich perm its safe engine operation at cooling
tem peratures o f u p to 256° F. w ith a 33% glycol solution.
When th e rad iato r cap is rem oved or loosened, the system
pressure drops to atm ospheric, an d the heat w hich had caused
w ater tem p eratu re to b e higher th a n 2 12°F , will be dissipated
b y conversion o f w ater to steam . Inasm uch as th e steam may
form in th e engine w ater passages, it will blow coolant o u t o f
th e rad iator u p per hose an d to p tank , necessitating coolant
replacem ent. Engine operating tem peratures higher th an the
norm al boiling p o in t o f w ater are in no w ay objectionable so
long as th e coolant level is satisfactory w hen the engine is cool.
U pon repeated coolant loss, the pressure radiator cap and
seat should be checked for sealing ability. Also, the cooling
system should be checked for loose hose connections, defec­
tive hoses, gasket leaks, etc.
Coolant System Checks
1. T est for restriction in the radiator, by warm ing the
engine up and th en turning th e engine o ff and feeling the
radiator. The radiator should be h ot at the to p (along the
left side o n crossflow radiators) and w arm at the b o tto m
(along the right side on crossflow radiators), w ith an even
tem perature rise from b o tto m to to p (right to left on
crossflow radiators). Cold spots in the radiator indicate
clogged sections.
2. W ater pum p op eration m ay be checked b y running the
engine while squeezing th e upper radiator hose. A
pressure surge should be felt. Check for a plugged
vent-hole in pum p.
N O T E : A defective head gasket may allow exhaust
gases to leak into the cooling system. This is
particularly damaging to the cooling system as the
gases combine w ith the water to fo rm acids which
are harm ful to both the radiator and engine.
MAINTENANCE AND
procedures are covered in this section. For rad iato r service
refer to Section 13 o f this m anual. R adiator fan shroud
replacem ent is covered in Section 11 o f this m anual.
ADJUSTMENTS
3. To check for exhaust leaks into the cooling system , drain
the system u n til the w ater level stands ju st above the top
o f th e cylinder head, th en disconnect the upper radiator
hose an d rem ove th e th erm o stat and fan belt. S tart the
engine and quickly accelerate several tim es. A t th e same
tim e n ote any appreciable w ater rise or th e appearance o f
bubbles w hich are indicative o f exhaust gases leaking into
the cooling system .
Periodic Maintenance
It is the ow ner's responsibility to keep the freeze protection
at a level com m ensurate w ith the area in w hich the vehicle will
be operated. Regardless o f clim ate, system protectio n should
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be m aintained at least to °F ., to provide adequate corrosion
p ro tectio n. When adding solution due to loss o f co olant for
any reason or in areas w here tem peratures low er th an -20° F.
may occur, a sufficient am ou nt o f an ethylene glycol base
coolant th a t m eets GM Specification 1899-M should be used.
Every tw o years th e cooling system should be serviced by
flushing w ith plain w ater, th en com pletely refilled w ith a fresh
solution o f w ater and high-quality inhibited (perm anent-type)
glycol base coolant m eeting GM Specification 1899-M, and
providing freezing p ro tectio n at least to 0 °F . A t this tim e, also
add GM Cooling System In h ib ito r and Sealer or equivalent. In
addition, Cooling System Inhibitor and Sealer should be added
every fall thereafter. GM Cooling System Inhibitor retards the
form ation o f rust or scale and is com patible w ith alum inum
com ponents.
N O T E : Alcohol or methanol base coolants or plain
water are not recommended fo r your cooling system
at any time.
Two com m on causes o f corrosion are: (1) air suction —
Air may be draw n into th e system due to low liquid level in
the radiator, leaky w ater pum p or loose hose connections; (
exhaust gas leakage — Exhaust gas may be blow n into the
cooling system past th e cylinder head gasket or through cracks
in the cylinder head and block.
Cleaning
A good cleaning solution should be used to loosen the rust
and scale before reverse flushing th e cooling system . There are
a num ber o f cleaning solutions available and th e m anufac­
tu rer's instructions w ith the particular cleaner being used
should always be follow ed.
An excellent preparation to use for this purpose is GM
Cooling System Cleaner or its equivalent. The following
directions for cleaning the system applies only w hen this type
cleaner is used.
1. D rain, the cooling system including th e cylinder block,
and th e n close drain plugs.
2. Remove th erm ostat an d replace therm o stat housing.
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C H E V Y V A N SHOP M A N U A L