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Sec. 6K-88
ENGINE COOLIN G SYSTEM
COOLING SYSTEM PROBLEM
ANALYSIS
1. Rem ove fille r cap or te ste r from fille r
neck so there w ill be no p r e ssu r e in sy stem , then
attach sy stem te ste r at fille r neck (fig. 1).
2. Start engine and run until norm al operating
tem perature is reached (approx. 175°F .).
3. O bserve gauge on te ste r . If no p r e ssu r e in
sy stem is indicated u se te ste r pump to p re ssu riz e
the sy stem . If sy stem w ill not hold p r essu re, in
spect h o ses, fittin gs, and gaskets. A lso, look for
water draining from hole in water pump body be
tween the pump se a l and the bearing.
4. If no lea k s are evident, it is p o ssib le that
coolant is leaking internally into crankcase, oil
co o ler, or com bustion cham bers.
5. To determ ine if there is coolant leakage
into oil coo ler or crankcase, look for water drop-
letm .on engine o il dipstick. A lso, look for engine
W ilkin cooling sy ste m which would indicate that
defective o il cooler or gaskets ex ist.
NOTE: R efer to applicable portion of SERIES
53 AND 71 DIESEL ENGINES (SEC. 6C) in this
supplement for "Testing and Problem A n a ly sis"
which gives additional information on detecting de
fective cooling sy ste m components on 53 and 71
S er ie s D ie se l engines.
ENGINE COOLANT
RECOMMENDATIONS
NOTE: Method of testin g, andprecau tion sp er
taining to cooling sy stem maintenance procedures
a re included in ENGINE COOLING SYSTEM (SEC.
6K)
in
Heavy
Duty
ST135-70,
with
supplem ental
RADIATOR AND SURGE TANK (SEC. 13) in this
supplem ent.
Recom m endations are for a high quality in
hibited Ethylene G lycol base coolant m eeting GM
Specifications 1899M and to provide the freezing
and corrosion protection (at le a st 0 °F .).
Additional inhibitors are not required on the
initial fill if a minimum antifreeze concentration
of 30% by volum e is used. Solutions of le s s than
30% concentration do not provide sufficient co rro
sion protection. Concentrations over 67% adversely
affect fr ee z e protection and heat tran sfer ra tes.
S everal brands of perm anent antifreeze are ava il
able with s e a le r additives. The sp ecific type of
s e a le r s vary with the m anufacturer. A ntifreeze
with se a le r additives is not recom m ended due to
plugging problem s throughout various a rea s of the
cooling sy stem .
NOTE: R efer to "Standard Cooling System
C apacities Chart" at the end of this section for
sy ste m capacities.
Truck
Service
Manual
inform ation
in
CO O LIN G SYSTEM CORROSION
PREVENTION
NOTE: Addition of supplem ental additives and
other available m aterials which have not been sp e c
ifica lly approved by GM are not norm ally required.
U se of th ese m aterials w ill resu lt in unwarranted
operating expense.
Every two y ea rs, the cooling sy ste m should
be serviced a s follow s:
1. Drain coolant, when hot, through the rad
iator drain valve.
2. C lose valve and add su fficient plain water
to fill sy stem .
3. Run engine until norm al operating tem per
ature is reached.
4. Drain and r efill the sy stem as described
in Steps 1, 2, and 3 a sufficient number of tim es
until the drained liquid is c o lo r le ss.
5. Allow sy stem to drain com pletely and then
c lo se radiator drain valve tightly.
6. Add the n ecessa ry amount of high quality
inhibited glycol base coolant m eeting GM S p ecifi
cation 1899-M to provide the required freezin g and
corrosion protection (at le a st to 0 °F .).
7. Run engine until norm al operating tem p er
ature is reached.
8. Check and adjust le v e l of coolant after s y s
tem has cooled sufficiently to rem ove radiator cap.
CAUTIO N : When an engine Is at norm
al operating temperature or above, the
internal p ressure built up in the cooling
system will blow out scalding fluid and
vapors if the radiator cap is suddenly r e
moved. To prevent loss of coolant and to
avoid the danger of being burned, the cool
ant level should be checked or coolant
added only when the engine is cool. To r e
move the cap when engine is cool, slowly
rotate cap counterclockwise to the stop on
f ille r neck (DONOT P R ESS DOWN W H ILE
RO TA TIN G ), wait until any residual p re s
sure is relieved - as Indicated by a h is s
ing sound, then p re ss down on the cap
while continuing to rotate counterclock
w ise. Radiator pressu re caps should be
checked by a qualified m echanic period
ica lly for proper operation and replaced
as required with the applicable AC type.
P re ssu re cap testing procedure is co ve r
ed previously in this section.
R egard less of whether freezin g tem peratures
are or are not expected, cooling sy ste m protection
should be m aintained at le a st to 0 ° F ., to provide
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT
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