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7/31/2019 Engine Cooling System Basics - Steve Ferguson
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BySteveFerguson
GMCWS Technical VP
7/31/2019 Engine Cooling System Basics - Steve Ferguson
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Componentsconsist
of:
1.Source
of
heat.
3.Water
pump. ermos a
5.Fan6. Expansiontank
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Ratherthanbuildse arate
radiatorsfor
each
source
of
heat,
t e ra ator asprov s ons
oilcooler.
Both
of
these
depend
oncoolantintheradiatorto
temperatures.
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Withoutsomemeansoflimitingtheflowofcoolantto
dissipateheat
from
these
sources,
they
would
never
be
abletogetuptooperationaltemperatures.
Thisis
where
the
thermostat
comes
into
play.
It
thereservoir/radiator. Aproperlyworkingthermostat
willopen
at
aspecific
temperature
and
regulate
flow
oncethesourceregainsthedesignoperating
temperature.
GMCsoriginallyhad195degreethermostatsinstalled
.
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WaterPum s
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isit
critical
that
the
impeller
have
an
anti
impeller.
Eachof
the
pumps
pictured
will
work
well.
Thenewwaterpumpshaveasmall,
stam edsteel
im eller
and
the
also
work
well.
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RadiatorCaps
Makesurethatwhicheverconfigurationyouchoose,itisrated
atnomorethan9lbs. Yourradiatorma beratedhi herthan
thatbut
your
unless
youve
replaced
your
heater
core,
it
is
also
ratedat9lbs.
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Theradiatorca hasafivefold ob:
. ,
2.Closure
cap
to
keep
coolant
in
the
radiator,
3.Pressurecaptopreventoverheatingbypressurizingthe
systemtoraisetheboilingtemperatureofcoolantandallow
theautomobile'senginetooperateatmoreefficienthigher
tem eratures
4.Pressurereliefvalvetosafelyandharmlesslyventexcess
pressureintotheoverflowjug,and
.
overflowjugbackintotheradiatortopreventairfromentering
thesystemandallowingthecoolanttoperformitsfunction
moreefficiently.
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expansiontanks
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s ecoo an ea sup, expan s. nce
reachesacertainpressureintheradiator,the
tension
spring
in
the
cap
and
allows
the
excess
coolantunderpressuretooverflowintothe
expansiontank,orrecoverytank.
ent ecoo anttemperature nt era ator
drops,thevolumeofthecoolantcontractscreating
radiatorfromtheexpansiontankthusmaintaining
acom letel filledradiator.
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, .
substitutes.
The
fan
is
coupled
to
the
water
pump
with
a
thermostaticallycontrolledclutch.
Itisnotnecessaryforthefantooperateat100%ofthe
enginerpm
at
all
times.
If
it
did,
the
engine
would
most
likelyneverreachproperoperatingtemperatureandthe
parasiticlossonpowerwouldsignificantlylowerMPG.
Enterthefanclutch
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yourcoolantAfterinitialfillup,andtheradiatorisfullandthe
capis
installed,
all
level
checking
should
be
done
at
.
throughitsheatingandcoolingcycles,coolant
neededto
replace
air
trapped
in
the
block
will
be
drawnfromtheexpansiontank. Thisiswhereyou
addcoolant. Removingtheradiatorcapwillresultin
lossof
s stem
balance
and
it
will
take
another
heating/coolingcycletoreestablishthisbalance.
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Whichoneisri ht?
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P/N154644forthe455engine
Andthe403engine
The
light
duty
AC
Delco
part
number
that
cross
references
to
the
OEM
fan
clutch
is:
P/N154223forthe455and
e
eng ne
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replacements.
Hayden,Murray,
NAPA,
.
Manyof
these
are
made
by
the
same
companyan aremar ete un er erent
brands.
Also,AC
Delco
outsources
some
of
itsfanclutchesandHaydenisoneofthe
sources.
Tor ueFlo
Autozone
fan
clutchesaremadebyHaydenandtheHD
.
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,
differencesbetween
different
models
and
a so erences e ween esamemo e s
withdifferent
manufactures.
First,thetestsetup!
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es ngwas
one
us ng
ap o o
ac ome er
totestfanspeedwiththefanclutch
, .
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disengaged,each
one
was
run
for
10
minutes
with
no
heata liedtothebimetalliccontrols rin s. U on
initialinstallationonthetestfixture,allclutchfans
werefullyengagedfromstorage.
Dynamic
testingconsisted
of
using
aphoto
tachometertorecordthespeedofthefanbladeand
themotordrivenpulleywiththefanclutchfully
sengage .
en
ea e
eme a c
con ro
springtofullyengagethefanclutchandagain
.
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FanClutchTestResults
Alltestin wasdoneusin a1h electricmotordrivin awater um witha7blade
3"pitch
5.5
fan.
ACDelco154644 #1
Enginerpm Fanrpm Enginerpm Fanrpm
1,292
1,000
1,268
1.238
ACDelco154644 #2
1,289
1,030
1,259
1,227
ACDelco154949
1,320 357 1,255 1,226
Hayden9727
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s
you
can
see
rom
e
num ers,
e
keyelementinperformanceisthe
percentageofrpmthatthefanspinsin
relationtoen iner m. Inthecaseof
theonesItested,theACDelcomodels
percentageofenginerpmwhile
clutches.
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Tempprobe
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Witha195RobertShawbalancedflowthermostatinstalled, aluminum
radiator,Curtisfullfanshroud,ambientairtempsinthelow80s,ItooktheGMCforatestdrive(withtheACon)todetermineatwhatairtemps(insidethe
, , .
Fanengages
Coolanttemp: 215deg Shroudairtemp:198deg
Coolanttemp: 200deg Shroudairtemp: 176
The154644clutchfanrespondsquicklytotheriseinshroudairtempswhen
thethermostatfullyopens. Typically,thecoolanttempplungeswhenthefan
engagesbutittakesafewmilesat65mphfortheclutchfanhousingtocool
enoughfor
the
clutch
to
fully
disengage.
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Inadditiontobenchtesting,ItestedallthelistedfanclutchesinmyGMC
.
range,some
stop
and
go,
and
sustained
speeds
of
65
mph.
_____________________________________
Insummary,ifyouliveinarelativelycoolclimate,youmaywanttoruntheHayden
. .
Whenengaged,itspinsatthesamepercentageofenginerpmastheheavydutyAC
Delcounits. ThisreducedparasiticdragcouldresultinalittlemoreMPG.
Inthe
hot
SW,
the
HD
AC
Delco
units
are
the
only
way
to
go.
Ifyouhaveanaluminumradiatorinstalled,themostefficientthermostatisthe190
degRobertShawbalancedflowunit. MrGasketperformancethermostatsarenot
recommended as the tend to o en sooner and close later resultin in constant fanclutchcycling. Thealuminumradiator,coupledwiththeACDelcoHD4644fan
clutch, theRSbalancedflowthermostat isthebestcombinationItested. This
combinationresultedinverystablecoolanttemperaturesandminimumclutchfan
cyc ng.