pedal. The proper course of action is to bleed the sys-
tem, or replace thin drums and suspect quality brake
lines and hoses.
HARD PEDAL OR HIGH PEDAL EFFORT
A hard pedal or high pedal effort may be due to lin-
ing that is water soaked, contaminated, glazed, or
badly worn. The power booster or check valve could
also be faulty. Test the booster and valve as described
in this section.
BRAKE DRAG
Brake drag occurs when the lining is in constant
contact with the rotor or drum. Drag can occur at one
wheel, all wheels, fronts only, or rears only. It is a
product of incomplete brakeshoe release. Drag can be
minor or severe enough to overheat the linings, ro-
tors and drums. A drag condition also worsens as
temperature of the brake parts increases.
Brake drag also has a direct effect on fuel economy.
If undetected, minor brake drag can be misdiagnosed
as an engine or transmission/torque converter prob-
lem.
Minor drag will usually cause slight surface char-
ring of the lining. It can also generate hard spots in
rotors and drums from the overheat/cool down pro-
cess. In most cases, the rotors, drums, wheels and
tires are quite warm to the touch after the vehicle is
stopped.
Severe drag can char the brake lining all the way
through. It can also distort and score rotors and
drums to the point of replacement. The wheels, tires
and brake components will be extremely hot. In se-
vere cases, the lining may generate smoke as it chars
from overheating.
An additional cause of drag involves the use of in-
correct length caliper mounting bolts. Bolts that are
too long can cause a partial apply condition. The cor-
rect caliper bolts have a shank length of 67 mm
(2.637 in.), plus or minus 0.6 mm (0.0236 in.). Refer
to the Disc Brake service section for more detail on
caliper bolt dimensions and identification.
Some common causes of brake drag are:
²loose or damaged wheel bearing
²seized or sticking caliper or wheel cylinder piston
²caliper binding on bolts or slide surfaces
²wrong length caliper mounting bolts (too long)
²loose caliper mounting bracket
²distorted rotor, brake drum, or shoes
²brakeshoes binding on worn/damaged support
plates
²severely rusted/corroded components
²misassembled components.
If brake drag occurs at all wheels, the problem may
be related to a blocked master cylinder compensatorport or faulty power booster (binds-does not release).
The condition will worsen as brake temperature in-
creases.
The brakelight switch can also be a cause of drag.
An improperly mounted or adjusted brakelight
switch can prevent full brake pedal return. The re-
sult will be the same as if the master cylinder com-
pensator ports are blocked. The brakes would be
partially applied causing drag.
BRAKE FADE
Brake fade is a product of overheating caused by
brake drag. However, overheating and subsequent
fade can also be caused by riding the brake pedal,
making repeated high deceleration stops in a short
time span, or constant braking on steep roads. Refer
to the Brake Drag information in this section for
causes.
PEDAL PULSATION (NON-ABS BRAKES ONLY)
Pedal pulsation is caused by parts that are loose,
or beyond tolerance limits. This type of pulsation is
constant and will occur every time the brakes are ap-
plied.
Disc brake rotors with excessive lateral runout or
thickness variation, or out of round brake drums are
the primary causes of pulsation.
On vehicles with ABS brakes, remember that pedal
pulsation is normal during antilock mode brake
stops. If pulsation occurs during light to moderate
brake stops, a standard brake part is either loose, or
worn beyond tolerance.
BRAKE PULL
A front pull condition could be the result of:
²contaminated lining in one caliper
²seized caliper piston
²binding caliper
²wrong caliper mounting bolts (too long)
²loose caliper
²loose or corroded mounting bolts
²improper brakeshoes
²damaged rotor
²incorrect wheel bearing adjustment (at one wheel)
A worn, damaged wheel bearing or suspension com-
ponent are further causes of pull. A damaged front
tire (bruised, ply separation) can also cause pull.
Wrong caliper bolts (too long) will cause a partial ap-
ply condition and pull if only one caliper is involved.
A common and frequently misdiagnosed pull condi-
tion is where direction of pull changes after a few
stops. The cause is a combination of brake drag fol-
lowed by fade at the dragging brake unit.
As the dragging brake overheats, efficiency is so re-
duced that fade occurs. If the opposite brake unit is
still functioning normally, its braking effect is magni-
5 - 6 SERVICE BRAKE DIAGNOSISJ
produce a condition similar to grab as the tire loses
and recovers traction.
Flat-spotted tires can cause vibration and wheel
tramp and generate shudder during brake operation.
A tire with internal damage such as a severe bruise
or ply separation can cause vibration and pull. The
pull will be magnified when braking.
DIAGNOSING PARKING BRAKE MALFUNCTIONS
Adjustment Mechanism
Parking brake adjustment is controlled by a ca-
ble tensioner mechanism. The cable tensioner,
once adjusted at the factory, will not need further
attention under normal circumstances. There are
only two instances when adjustment is required.
The first is when a new tensioner, or cables have
been installed. And the second, is when the ten-
sioner and cables are disconnected for access to
other brake components.
Parking Brake Switch And Warning Light Illumination
The parking brake switch on the lever, or foot
pedal, is in circuit with the red warning light. The
switch will illuminate the red light only when the
parking brakes are applied. If the light remains on
after parking brake release, the switch or wires are
faulty, or cable tensioner adjustment is incorrect.
If the red light comes on while the vehicle is in mo-
tion and brake pedal height decreases, a fault has oc-
curred in the front or rear brake hydraulic system.
Parking Brake problem Causes
In most cases, the actual cause of an improperly
functioning parking brake (too loose/too tight/wont
hold), can be traced to a drum brake component.
The leading cause of improper parking brake
operation, is excessive clearance between the
brakeshoes and the drum surface. Excessive
clearance is a result of: lining and/or drum
wear; oversize drums; or inoperative shoe ad-
juster components.
Excessive parking brake lever travel (sometimes de-
scribed as a loose lever or too loose condition), is the re-
sult of worn brakeshoes/drums, improper brakeshoe
adjustment, or incorrectly assembled brake parts.
A ``too loose'' condition can also be caused by inop-
erative brakeshoe adjusters. If the adjusters are mis-
assembled, they will not function. In addition, since
the adjuster mechanism only works during reverse
stops, it is important that complete stops be made.
The adjuster mechanism does not operate when roll-
ing stops are made in reverse. The vehicle must be
brought to a complete halt before the adjuster lever
will turn the adjuster screw.
A condition where the parking brakes do not hold, will
most probably be due to a wheel brake component.
Items to look for when diagnosing a parking brake
problem, are:
²rear brakeshoe wear or adjuster problem
²rear brake drum wear
²brake drums machined beyond allowable diameter
(oversize)
²parking brake front cable not secured to lever
²parking brake rear cable seized
²parking brake strut reversed
²parking brake strut not seated in both shoes
²parking brake lever not seated in secondary shoe
²parking brake lever or brakeshoe bind on support
plate
²brakeshoes reversed
²adjuster screws seized
²adjuster screws reversed
²holddown or return springs misassembled or lack
tension
²wheel cylinder pistons seized
Brake drums that are machined oversize are diffi-
cult to identify without inspection. If oversize drums
are suspected, diameter of the braking surface will
have to be checked with an accurate drum gauge.
Oversize drums will cause low brake pedal and lack
of parking brake holding ability.
Improper parking brake strut and lever installation
will result in unsatisfactory parking brake operation.
Intermixing the adjuster screws will cause drag, bind
and pull along with poor parking brake operation.
Parking brake adjustment and parts replacement pro-
cedures are described in the Parking Brake section.
MASTER CYLINDER/POWER BOOSTER TEST
(1) Start engine and check booster vacuum hose
connections. Hissing noise indicates vacuum leak.
Correct any vacuum leak before proceeding.
(2) Stop engine and shift transmission into Neu-
tral.
(3) Pump brake pedal until all vacuum reserve in
booster is depleted.
(4) Press and hold brake pedal under light foot
pressure.
(a) If pedal holds firm, proceed to step (5).
(b) If pedal does not hold firm and falls away,
master cylinder is faulty due to internal leakage.
Overhaul or replace cylinder.
(5) Start engine and note pedal action.
(a) If pedal falls away slightly under light foot
pressure then holds firm, proceed to step (6).
(b) If no pedal action is discernible, or hard pedal
is noted, power booster or vacuum check valve is
faulty. Install known good check valve and repeat
steps (2) through (5).
(6) Rebuild booster vacuum reserve as follows: Re-
lease brake pedal. Increase engine speed to 1500
rpm, close throttle and immediately turn off ignition.
5 - 8 SERVICE BRAKE DIAGNOSISJ
POWER BRAKE BOOSTER OPERATION
Booster Components
The booster assembly consists of a housing divided
into separate chambers by two internal diaphragms
(Fig. 2). The outer edge of each diaphragm is at-
tached to the booster housing. The diaphragms are
connected to the booster primary push rod.
Two push rods are used in the booster. The primary
push rod connects the booster to the brake pedal. The
secondary push rod connects the booster to the mas-
ter cylinder to stroke the cylinder pistons.
The atmospheric inlet valve is opened and closed
by the primary push rod. Booster vacuum supply is
through a hose attached to an intake manifold fitting
at one end and to the booster check valve at the
other. The vacuum check valve in the booster housing
is a one-way device that prevents vacuum leak back.How Brake Boost Is Generated
Power assist is generated by utilizing the pressure
differential between normal atmospheric pressure
and a vacuum. The vacuum needed for booster oper-
ation is taken directly from the engine intake mani-
fold. The entry point for atmospheric pressure is
through a filter and inlet valve at the rear of the
housing (Fig. 3).
The chamber areas forward of the booster dia-
phragms are exposed to vacuum from the intake
manifold. The chamber areas to the rear of the dia-
phragms, are exposed to normal atmospheric pres-
sure of 101.3 kilopascals (14.7 pounds/square in.).
Brake pedal application causes the primary push
rod to open the atmospheric inlet valve. This exposes
the area behind the diaphragms to atmospheric pres-
sure. The resulting pressure differential provides the
extra apply pressure for power assist.
Fig. 2 Brake Booster/Master Cylinder Assembly (YJ)
JPOWER BRAKE BOOSTERÐBRAKE PEDALÐBRAKELIGHT SWITCH 5 - 23
(16) Install combination valve as follows:
(a) Work combination valve and brakelines into
position.
(b) Slide combination valve bracket onto booster
stud closest to driver side fender (Fig. 25). Then in-
stall bracket attaching nut but do not fully tighten
nut at this time.
(c) Connect flex lines to HCU. Start lines by
hand to avoid cross threading.
(17) Swing rear brakeline around and connect it to
master cylinder. Then install and connect front
brakeline to combination valve and master cylinder.
Start brakelines by hand to avoid cross threading.
(18) Tighten combination valve bracket attaching
nut to 25 Nzm (220 in. lbs.) torque.
(19) Install clip on lines from master cylinder to
combination valve.
(20) Connect wire to pressure differential switch
on combination valve.
(21) Connect flex lines to HCU (Fig. 10). Start line
fittings by hand to avoid cross threading. Then
tighten fittings snug but not to required torque at
this time.(22) Bleed brakes. Refer to procedure in Brake
Fluid-Brake Bleeding-Brakelines And Hoses section.
(23) Tighten brakeline fittings to 15-18 Nzm (130-
160 in. lbs.) at HCU and master cylinder, and 18-24
Nzm (160-210 in. lbs.) at combination valve.
(24) Install air cleaner assembly.
(25) Connect vacuum lines to manifold fittings.
(26) Check brake pedal action before moving vehi-
cle. Bleed brakes again if pedal is not firm (feels soft/
spongy).POWER BRAKE BOOSTER REMOVAL (XJ WITHOUT
ABS)
(1) Disconnect vent and vacuum hose from engine
air cleaner cover.
(2) Remove engine air cleaner cover, filter, housing
and hoses (Fig. 4).
(3) Disconnect brakelines at master cylinder.
(4) Disconnect wire at combination valve differen-
tial pressure switch.
(5) If combination valve does not have an integral
bracket, disconnect brakelines at combination valve
and remove valve.
(6) If combination valve has integral bracket, re-
move nut attaching valve bracket to booster studs
and remove valve.
(7) Remove nuts attaching master cylinder to
booster studs and remove cylinder.
(8) Disconnect vacuum hose from booster check
valve.
(9) In passenger compartment, remove instrument
panel lower trim cover.
(10) Remove retaining clip that secures booster
push rod to brake pedal (Fig. 5).
Fig. 23 HCU And Bracket Mounting (RHD Models)
Fig. 24 Starting Brakelines In HCU
Fig. 25 Combination Valve Installation
JPOWER BRAKE BOOSTERÐBRAKE PEDALÐBRAKELIGHT SWITCH 5 - 29
(11) Remove nuts attaching booster to passenger
compartment side of dash panel.
(12) In engine compartment, slide booster studs
out of dash panel, tilt booster upward, and remove
booster from engine compartment.
(13) Remove dash seal from booster.
(14) If booster is only being removed for access to
other components, cover booster front opening with
clean shop towel.
POWER BRAKE BOOSTER INSTALLATION (XJ
WITHOUT ABS)
(1) If original booster is being installed, test check
valve with vacuum tool before booster installation.
Replace check valve if it will not hold vacuum.
(2) Install dash seal on booster.
(3) Align and position booster on dash panel (Fig.
17).
(4) In passenger compartment, install nuts that at-
tach booster to dash panel. Tighten nuts just enough
to hold booster in place.
(5) Slide booster push rod onto brake pedal. Then
secure push rod to pedal pin with retaining clip.
(6) Tighten booster attaching nuts to 41 Nzm (30 ft.
lbs.) on XJ and 34 Nzm (25 ft. lbs.) on YJ.
(7) Install instrument panel lower trim cover.
(8) If original master cylinder is being installed,
check condition of seal at rear of master cylinder
(Fig. 18). Clean and reposition seal if dislodged. Re-
place seal if cut, or torn.
(9) Clean cylinder mounting surface of brake
booster. Use shop towel wetted with brake cleaner for
this purpose. Dirt, grease, or similar materials will
prevent proper cylinder seating and could result in
vacuum leak.
(10) Align and install master cylinder on booster
studs. Tighten cylinder attaching nuts to 13-25 Nzm
(115-220 in. lbs.) torque.
(11) Connect vacuum hose to booster check valve.
(12) Connect and secure brakelines to combination
valve and master cylinder. Start all brakeline fittings
by hand to avoid cross threading.
(13) If combination valve has integral bracket, po-
sition bracket on booster studs. Then install and
tighten bracket attaching nuts to 13-25 Nzm (115-220
in. lbs.) torque.
(14) Connect wire to combination valve switch.
(15) Top off master cylinder fluid level.
(16) Bleed brakes. Refer to procedures in section
on brake bleeding.
(17) Install engine air cleaner and hoses.
(18) Verify proper brake operation before moving
vehicle.
POWER BRAKE BOOSTER REMOVAL (YJ)
(1) Disconnect brakelines at master cylinder. Then
loosen lines at combination valve and move lines
away from cylinder.
(2) Remove nuts master cylinder to booster studs.
(3) If combination valve has integral bracket, slide
bracket off studs and move valve aside.
(4) Remove master cylinder. Slide cylinder off
studs and remove it from engine compartment.
(5) Working under instrument panel, remove re-
tainer clip that secures booster push rod to brake
pedal.
(6) Disconnect vacuum hose at booster check valve.
(7) On non-ABS models, remove nuts attaching
brake booster spacer to dash panel and remove
booster (Fig. 26).
(8) On ABS models, remove nuts attaching booster
to spacer and remove booster (Fig. 27).
POWER BRAKE BOOSTER INSTALLATION (YJ)
(1) Install seal on booster spacer, if equipped.
(2) Position booster on dash panel, or on spacer.
(3) Secure booster push rod to brake pedal with re-
taining clip.
(4) Install and tighten booster attaching nuts to
27-47 Nzm (20-35 ft. lbs.) torque. Nut torque applies
to both styles of booster.
Fig. 26 Booster Mounting (4-Cyl. Models)
Fig. 27 Booster Mounting (With ABS)
5 - 30 POWER BRAKE BOOSTERÐBRAKE PEDALÐBRAKELIGHT SWITCHJ
(4) Position clutch disc on flywheel. Be sure side of
disc marked flywheel side is positioned against fly-
wheel (Fig. 2). If disc is not marked, be sure flat side
of disc hub is toward flywheel.
(5) Inspect condition of pressure plate surface of
clutch cover (Fig. 2). Replace cover if this surface is
worn, heat checked, cracked, or scored.
(6) Insert clutch alignment tool in clutch disc (Fig.
3).
(7) Insert alignment tool in pilot bearing and posi-
tion disc on flywheel. Be sure disc hub is positioned
correctly. Side of hub marked Flywheel Side should
face flywheel (Fig. 2). If disc is not marked, place flat
side of disc against flywheel.
(8) Position clutch cover over disc and on flywheel
(Fig. 3).
(9) Install clutch cover bolts finger tight.(10) Tighten cover bolts evenly and in rotation a
few threads at a time.Cover bolts must be tight-
ened evenly and to specified torque to avoid
distorting cover. Tightening torques are 31 Nzm
(23 ft. lbs.) on 2.5L engines and 54 Nzm (40 ft.
lbs.) on 4.0L engines.
(11) Apply light coat of Mopar high temperature
bearing grease to pilot bearing hub and splines of
transmission input shaft.Do not overlubricate
shaft splines. This will result in grease contam-
ination of disc.
(12) Install transmission (Figs. 4 and 5). Refer to
procedures in Group 21.
RELEASE BEARING REPLACEMENT
(1) Remove transmission as described in Group 21.
Fig. 2 Clutch Disc And Pressure Plate InspectionFig. 3 Typical Method Of Aligning Clutch Disc
Fig. 4 Manual Transmission Mounting (4.0L)
JCLUTCH SERVICE 6 - 11
EXAMPLES:
²If the lamp (Figs. 5 or 6) flashes 1 time, pauses
and flashes 2 more times, a flashing Diagnostic Trou-
ble Code (DTC) number 12 is indicated. If this code is
observed, it is indicating that the battery has been
disconnected within the last 50 key-on cycles. It
could also indicate that battery voltage has been dis-
connected to the PCM. In either case, other DTC's
may have been erased.
²If the lamp flashes 1 time, pauses and flashes 7
more times, a flashing Diagnostic Trouble Code
(DTC) number 17 is indicated.
²If the lamp flashes 3 times, pauses and flashes 5
more times, a flashing Diagnostic Trouble Code
(DTC) number 35 is indicated.
After any stored DTC information has been ob-
served, the display will end with a flashing DTC
number 55. This will indicate the end of all stored in-
formation.
ERASING TROUBLE CODES
After the problem has been repaired, the DRB scan
tool must be used to erase a DTC. Refer to the ap-
propriate Powertrain Diagnostic Procedures service
manual for operation of the DRB scan tool.
DRB SCAN TOOL
For operation of the DRB scan tool, refer to the ap-
propriate Powertrain Diagnostic Procedures service
manual.
PRELIMINARY CHECKS
ENGINE COOLING SYSTEM OVERHEATING
Establish what driving conditions caused the com-
plaint. Abnormal loads on the cooling system such as
the following may be the cause.
1. PROLONGED IDLE, VERY HIGH AMBIENT
TEMPERATURE, SLIGHT TAIL WIND AT IDLE,
SLOW TRAFFIC, TRAFFIC JAMS, HIGH
SPEED, OR STEEP GRADES:
Driving techniques that avoid overheating are:
²Idle with A/C off when temperature gauge is at
end of normal range.
²Increasing engine speed for more air flow is recom-
mended.
2. TRAILER TOWING:
Consult Trailer Towing section of owners manual.
Do not exceed limits.
3. AIR CONDITIONING; ADD-ON OR AFTER
MARKET:
A maximum cooling package should have been or-
dered with vehicle if add-on or after market A/C is
installed. If not, maximum cooling system compo-
nents should be installed for model involved per
manufacturer's specifications.
4. RECENT SERVICE OR ACCIDENT REPAIR:
Determine if any recent service has been performed
on vehicle that may effect cooling system. This may
be:
²Engine adjustments (incorrect timing)
²Slipping engine accessory drive belt(s)
²Brakes (possibly dragging)
²Changed parts (incorrect water pump rotating in
wrong direction)
²Reconditioned radiator or cooling system refilling
(possibly under-filled or air trapped in system).
If investigation reveals none of the previous
items as a cause for an engine overheating com-
plaint, refer to following Cooling System Diag-
nosis charts.
These charts are to be used as a quick-reference
only. Refer to the group text for information.
Fig. 7 Data Link ConnectorÐXJ ModelsÐTypical
Fig. 8 Data Link ConnectorÐYJ ModelsÐTypical
JCOOLING SYSTEM DIAGNOSIS 7 - 5
COOLANT
GENERAL INFORMATION
The cooling system is designed around the coolant.
Coolant flows through the engine water jackets ab-
sorbing heat produced during engine operation. The
coolant carries heat to the radiator and heater core.
Here it is transferred to the ambient air passing
through the radiator and heater core fins. The cool-
ant also removes heat from the automatic transmis-
sion fluid in vehicles equipped with an automatic
transmission.
COOLANT PERFORMANCE
The required ethylene-glycol (antifreeze) and water
mixture depends upon climate and vehicle operating
conditions. The coolant performance of various mix-
tures follows:
Pure Water-Water can absorb more heat than a
mixture of water and ethylene-glycol. This is for pur-
pose of heat transfer only. Water also freezes at a
higher temperature and allows corrosion.
100 percent Ethylene-Glycol-The corrosion in-
hibiting additives in ethylene-glycol need the pres-
ence of water to dissolve. Without water, additives
form deposits in system. These act as insulation
causing temperature to rise to as high as 149ÉC
(300ÉF). This temperature is hot enough to melt plas-
tic and soften solder. The increased temperature can
result in engine detonation. In addition, 100 percent
ethylene-glycol freezes at -22ÉC (-8ÉF).
50/50 Ethylene-Glycol and Water-Is the recom-
mended mixture, it provides protection against freez-
ing to -37ÉC (-35ÉF). The antifreeze concentration
must alwaysbe a minimum of 44 percent, year-
round in all climates. If percentage is lower, engine
parts may be eroded by cavitation. Maximum protec-
tion against freezing is provided with a 68 percent
antifreeze concentration, which prevents freezing
down to -67.7ÉC (-90ÉF). A higher percentage will
freeze at a warmer temperature. Also, a higher per-
centage of antifreeze can cause the engine to over-
heat because specific heat of antifreeze is lower than
that of water.
CAUTION: Richer antifreeze mixtures cannot be
measured with normal field equipment and can
cause problems associated with 100 percent ethyl-
ene-glycol.
COOLANT SELECTION-ADDITIVES
Coolant should be maintained at the specified level
with a mixture of ethylene glycol-based antifreeze
and low mineral content water. Only use an anti-
freeze containing ALUGARD 340-2 Ÿ.CAUTION: Do not use coolant additives that are
claimed to improve engine cooling.
COOLANT SERVICE
It is recommended that the cooling system be
drained and flushed at 84,000 kilometers (52,500
miles), or 3 years, whichever occurs first. Then every
two years, or 48,000 kilometers (30,000 miles),
whichever occurs first.
COOLANT LEVEL CHECKÐROUTINE
Do not remove radiator cap for routine cool-
ant level inspections. The coolant level can be
checked at coolant reserve/overflow tank.
The coolant reserve/overflow system provides a
quick visual method for determining coolant level
without removing radiator pressure cap. With engine
idling and at normal operating temperature, observe
coolant level in reserve/overflow tank. The coolant
level should be between ADD and FULL marks.
ADDING ADDITIONAL COOLANTÐROUTINE
Do not remove radiator cap to add coolant to
system.When adding coolant to maintain correct
level, do so at coolant reserve/overflow tank. Use a
50/50 mixture of ethylene-glycol antifreeze containing
Alugard 340-2 Ÿ and low mineral content water. Re-
move radiator cap only for testing or when refilling
system after service. Removing cap unnecessarily can
cause loss of coolant and allow air to enter system,
which produces corrosion.
COOLANT LEVEL CHECK-SERVICE
The cooling system is closed and designed to main-
tain coolant level to top of radiator.
WARNING: DO NOT OPEN RADIATOR DRAINCOCK
WITH ENGINE RUNNING OR WHILE ENGINE IS HOT
AND COOLING SYSTEM IS UNDER PRESSURE.
When vehicle servicing requires a coolant level
check in radiator, drain several ounces of coolant
from radiator drain cock. Do this while observing
coolant reserve/overflow system tank. The coolant
level in reserve/overflow tank should drop slightly. If
not, inspect for a leak between radiator and coolant
reserve/overflow system connection. Remove radiator
cap. The coolant level should be to top of radiator. If
not and if coolant level in reserve/overflow tank is at
ADD mark, check for:
²An air leak in coolant reserve/overflow tank or its
hose
²An air leak in radiator filler neck
²Leak in pressure cap seal to radiator filler neck
LOW COOLANT LEVEL-AERATION
If the coolant level in radiator drops below top of
radiator core tubes, air will enter cooling system.
7 - 20 COOLING SYSTEM SERVICE PROCEDURESJ