Sec. 6K
P age 19
b. F ill cooling sy ste m to le v e l of f ille r cap
se a t.
c . Attach t e s te r to f ille r neck follow ing the
in stru ctio n s supplied with te s te r .
d. B uild p r e s s u r e up to 20 p si (m axim um ).
e. The cooling sy ste m should hold the 20 p si
p r e s s u r e for approxim ately two m inutes. If p r e s
su re drops appreciably in le s s than two m inutes, a
leak in sy ste m is indicated.
COOLING SYSTEM PROBLEM
ANALYSIS
1. R em ove fille r cap or te s te r fro m f ille r
neck so th ere w ill be no p r e s s u r e in sy ste m , then
attach sy ste m te s te r at fille r neck (fig. 1).
2. Start engine and run until norm al operating
tem p eratu re is reached (approx. 175 F .).
3. O bserve gauge on t e s te r . If no p r e s s u r e in
s y s te m is in d icated ,u se te s te r pump to p r e s s u r iz e
the s y ste m . If sy ste m w ill not hold p r e s s u r e , in
sp ect h o se s, fittin g s, and g a sk e ts. A lso , look for
w ater draining from hole in w ater pump body b e
tw een the pump s e a l and the bearing.
4. If no lea k s a r e evident, it is p o ssib le that
coolant is leaking internally into cra n k ca se, o il
c o o le r , or com bustion cham bers.
5. To determ ine if th ere is coolant leakage
into o il co o ler or cran k case, look for w ater drop
le ts on engine o il dipstick. A lso , look for engine
o il in cooling s y s te m which would indicate that
d efectiv e o il co o ler or g a sk ets e x ist.
ENGINE COOLANT
RECOMMENDATIONS
R ecom m endations a re for a high quality in
hibited Ethylene G lycol B a se Coolant m eeting GM
S p ecifica tio n s 1899M and to provide the freezin g
and co rro sio n p rotection (at le a s t 0 F .).
Additional inhibitors a re not required on in itial
f ill if a m inim um a n tifreeze concentration of 30%
by volum e is u sed . Solutions of l e s s than 30% con
centration do not provide su fficien t co rro sio n p ro
tectio n . C oncentrations over 67% a d v ersely affect
f r e e z e protection and heat tra n sfer r a te s. S everal
brands of perm anent a n tifreeze a re availab le with
s e a le r ad d itives. The s p e c ific type of s e a le r s vary
with the m anufacturer. A n tifreeze with s e a le r ad
d itiv e s is not recom m en ded due to plugging prob
le m s throughout v ariou s a r e a s of the cooling sy ste m .
NOTE: R efer to ’’C ooling System C ap acities
C hart” at the end of th is se c tio n for sy ste m ca
p a c itie s .
ENGINE COOLING SYSTEM
COOLING SYSTEM CORROSION
PREVENTION
NOTE: Addition of supplem ental ad d itives and
other availab le m a teria ls which have not been s p e c
ific a lly approved by GM are not norm ally req u ired .
U se of th ese m a teria ls w ill r e su lt in unwarranted
operating exp en se.
E very two y e a r s, the cooling s y s te m should
be s e r v ic e d a s follow s:
1. D rain coolant, when hot, through the rad
iator drain v alve.
2. C lo se valve and add su fficien t plain w ater
to f ill sy ste m .
3. Run engine until norm al operating tem p er
ature is reached.
4. D rain and r e fill the sy ste m a s d escrib ed
in Steps 1, 2, and 3 a su fficien t number of tim e s
until the drained liquid is c o lo r le s s .
5. A llow sy ste m to drain com p letely and then
c lo s e radiator drain valve tightly.
6. Add the n e c e ssa r y amount of high quality
inhibited gly co l b a se coolant m eeting GM S p eci
fication 1899-M to provide the required fr e e z in g
and co rro sio n protection (at le a s t to 0 ° F .).
7. Run engine until norm al operating te m p e r
ature is reached.
8. Check and adjust le v e l of coolant after s y s
tem has cooled su fficien tly to rem ove radiator cap.
C A U TIO N : When an engine Is at norm
al operating temperature or above, the
internal pressure built up in the cooling
system will blow out scalding fluid and
vapors if the radiator cap is suddenly re
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 remove the cap when engine is
cool, slowly rotate cap counterclockw ise
to the stop on fille r neck (DO NOT P R E S S
DOWN W H ILE R O TA TIN G ), wait until any
residual pressure is relieved - as indicat
ed by a hissing sound, then press down on
the cap while continuing to rotate counter
clockw ise.
Radiator pressure caps should be
checked by a qualified m echanic period
ically for proper operation and replaced
as required with the applicable A C type.
P re ssu re cap testing procedure is co v e r-
ed previously In this section.______________
R e g a rd less of whether freezin g tem p era tu res
a r e or a re not expected, cooling s y s te m p rotection
should be m aintained at le a s t to 0 ° F ., to provide
adequate c o r ro sio n p rotection . When coolant addi-
