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COOLING SYSTEM

7-1

COOLING SYSTEM

CONTENTS

page

GENERAL INFORMATION

COOLANT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

COOLANT TANK . . . . . . . . . . . . . . . . . . . . . . . . . 2

COOLING SYSTEM . . . . . . . . . . . . . . . . . . . . . . . 1

ENGINE ACCESSORY DRIVE BELTS . . . . . . . . . . 2

LOW COOLANT LEVEL SENSOR . . . . . . . . . . . . 3

RADIATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

WATER PUMP . . . . . . . . . . . . . . . . . . . . . . . . . . 3

DESCRIPTION AND OPERATION

AUTOMATIC BELT TENSIONER . . . . . . . . . . . . . 6

BELT TENSION . . . . . . . . . . . . . . . . . . . . . . . . . . 6

COOLANT PERFORMANCE . . . . . . . . . . . . . . . . . 4

COOLING SYSTEM HOSES . . . . . . . . . . . . . . . . . 5

PRESSURE/VENT CAP . . . . . . . . . . . . . . . . . . . . 4

THERMOSTAT . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

VISCOUS FAN DRIVE . . . . . . . . . . . . . . . . . . . . . 6

DIAGNOSIS AND TESTING

BELT DIAGNOSIS . . . . . . . . . . . . . . . . . . . . . . . 16

LOW COOLANT LEVEL- AERATION . . . . . . . . . 15

PRELIMINARY CHECKS . . . . . . . . . . . . . . . . . . . 7

PRESSURE/VENT CAP . . . . . . . . . . . . . . . . . . . 15

RADIATOR COOLANT FLOW CHECK . . . . . . . . 13

TESTING COOLING SYSTEM FOR LEAKS . . . . 13

THERMOSTAT . . . . . . . . . . . . . . . . . . . . . . . . . . 13

VISCOUS FAN DRIVE . . . . . . . . . . . . . . . . . . . . 13

SERVICE PROCEDURES

COOLANT LEVEL CHECK . . . . . . . . . . . . . . . . .

COOLANT REPLACEMENT . . . . . . . . . . . . . . . .

DRAINING COOLING SYSTEM . . . . . . . . . . . . .

REFILLING COOLING SYSTEM . . . . . . . . . . . . .

REMOVAL AND INSTALLATION

AUTOMATIC BELT TENSIONER . . . . . . . . . . . .

DRIVE BELT . . . . . . . . . . . . . . . . . . . . . . . . . . .

FAN BLADE REMOVAL . . . . . . . . . . . . . . . . . . .

RADIATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . .

THERMOSTAT . . . . . . . . . . . . . . . . . . . . . . . . . .

VISCOUS FAN DRIVE . . . . . . . . . . . . . . . . . . . .

WATER PUMP . . . . . . . . . . . . . . . . . . . . . . . . .

CLEANING AND INSPECTION

COOLING SYSTEM CLEANING/REVERSE

FLUSHING . . . . . . . . . . . . . . . . . . . . . . . . . . .

FAN BLADE . . . . . . . . . . . . . . . . . . . . . . . . . . .

PRESSURE/VENT CAP . . . . . . . . . . . . . . . . . . .

RADIATOR CLEANING . . . . . . . . . . . . . . . . . . .

WATER PUMP . . . . . . . . . . . . . . . . . . . . . . . . .

SPECIFICATIONS

COOLING SYSTEM CAPACITY . . . . . . . . . . . . .

THERMOSTAT . . . . . . . . . . . . . . . . . . . . . . . . . .

TORQUE SPECIFICATIONS . . . . . . . . . . . . . . . .

COOLING SYSTEM COMPONENTS

GENERAL INFORMATION

COOLING SYSTEM

The cooling system regulates engine operating tem-

perature. It allows the engine to reach normal oper-

ating temperature as quickly as possible, maintains

normal operating temperature and prevents over-

heating.

The cooling system also provides a means of heat-

ing the passenger compartment. The cooling system

is pressurized and uses a centrifugal water pump to

circulate coolant throughout the system. A water

manifold collects coolant from the cylinder heads. A

separate and remotely mounted, pressurized coolant

tank using a pressure/vent cap is used.

The cooling system consists of:

•

Charge Air Cooler

•

Electric Cooling Fan

•

A brass-core radiator with plastic side tanks

•

A radiator mounted fill vent valve

•

A separate pressurized coolant tank

•

A threaded-on, pressure/vent cap mounted to the

coolant tank

•

Cooling fan (mechanical)

•

Thermal viscous fan drive

•

Fan shroud

•

Thermostat

•

Coolant

•

Low coolant level sensor

•

Low coolant warning lamp

•

Coolant temperature gauge

•

Water pump

7-2

COOLING SYSTEM

GENERAL INFORMATION (Continued)

•

Hoses and hose clamps

automatic belt tensioner is used to maintain correct

belt tension at all times.

CAUTION: When installing a serpentine accessory

drive belt, the belt MUST be routed correctly. If not,

the engine may overheat due to water pump rotat-

ing in wrong direction. Refer to the engine Belt

Schematic in Specification section at the end of this

group for the correct belt routing.

COOLANT ROUTING

For cooling system flow routing, refer to (Fig. 1).

RADIATOR

The radiator used with the 2.5L diesel is con-

structed of a horizontal down-flow brass core with

plastic side tanks.

CAUTION: Plastic tanks, while stronger than brass,

are subject to damage by impact, such as

wrenches.

COOLANT TANK

A pressurized, plastic coolant tank is used with the

cooling system. This separate tank should be consid-

ered part of the radiator. The tank is located at the

right-rear side of the engine compartment and is

mounted as the highest point of the cooling system.

This will allow any air or vapor exceeding the pres-

ENGINE ACCESSORY DRIVE BELTS

The accessory drive components are operated by a

single, crankshaft driven, serpentine drive belt. An

Fig. 1 Coolant Flow—2.5L Diesel Engine—Typical

GENERAL INFORMATION (Continued)

sure/vent cap rating to escape through the cap. Cool-

ant will flow through the tank at all times during

engine operation whether the engine is cold or at

normal operating temperature. The coolant tank is

equipped with a threaded pressure/vent cap. Refer to

Pressure/Vent Cap for additional information.

The low coolant level sensor is located on the bot-

tom of the tank.

COOLING SYSTEM

7-3

WATER PUMP

A centrifugal water pump circulates coolant

through the water jackets, passages, water manifold,

radiator core, pressurized coolant tank, cooling sys-

tem hoses and heater core. The pump is driven from

the engine crankshaft by a drive belt. The water

pump is bolted to the water pump adapter (Fig. 2).

The water pump adapter is bolted to the engine.

The water pump impeller is pressed onto the rear

of a shaft that rotates in bearings pressed into the

housing. The bottom of the housing is equipped with

a small vent tube (Fig. 2) to allow seepage to escape.

A drain hose is attached to this tube. The water

pump seals are lubricated by the antifreeze in the

coolant mixture. No additional lubrication is neces-

sary.

A rubber o-ring (instead of a gasket) is used as a

seal between the water pump and the water pump

adapter (Fig. 2).

A quick test to determine if the pump is working is

to check if the heater warms properly. A defective

water pump will not be able to circulate heated cool-

ant through the long heater hose to the heater core.

Fig. 2 Water Pump— Typical

COOLANT

Coolant flows through the engine water jackets

and water manifold absorbing 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.

LOW COOLANT LEVEL SENSOR

The low coolant level sensor checks for low coolant

level in the coolant tank. A signal will be sent from

this sensor to the powertrain control module (PCM).

When the PCM determines low coolant level, the

instrument panel mounted low coolant level warning

lamp will be illuminated. The sensor is located on the

front side of the coolant tank (Fig. 3). For informa-

tion, refer to Group 8E, Instrument Panel and

Gauges.

If this lamp is illuminated, it indicates the need for

service.

Fig. 3 Low Coolant Level Sensor

DESCRIPTION AND OPERATION

THERMOSTAT

A pellet-type thermostat controls the operating

temperature of the engine by controlling the amount

of coolant flow to the radiator. The thermostat starts

to open at 80°C (176°F). Above this temperature,

coolant is allowed to flow to the radiator. This pro-

7-4

COOLING SYSTEM

DESCRIPTION AND OPERATION (Continued)

vides quick engine warmup and overall temperature

control.

The same thermostat is used for winter and sum-

mer seasons. An engine should not be operated with-

out a thermostat, except for servicing or testing.

Operating without a thermostat causes other prob-

lems. These are: longer engine warmup time, unreli-

able warmup performance, increased exhaust

emissions and crankcase condensation. This conden-

sation can result in sludge formation.

CAUTION: Do not operate an engine without a ther-

mostat, except for servicing or testing.

PRESSURE/VENT CAP

The pressure/vent cap is threaded-on to the coolant

tank. This cap releases excess pressure at some point

within a range of 90-117 kPa (13- 17 psi). The actual

pressure relief point (in pounds) is labeled on top of

the cap (Fig. 4).

The cooling system will operate at pressures

slightly above atmospheric pressure. This results in a

higher coolant boiling point allowing increased radi-

ator cooling capacity. The cap (Fig. 4) contains a

spring-loaded pressure relief valve. This valve opens

when system pressure reaches approximately 103

kPa (15 psi).

When the engine is cooling down, vacuum is

formed within the cooling system. To prevent collapse

of the radiator and coolant hoses from this vacuum, a

vacuum valve is used within the cap. This valve pre-

vents excessive pressure differences from occurring

between the closed cooling system and the atmo-

sphere. If the vacuum valve is stuck shut, the radia-

tor and/or cooling system hoses will collapse on cool-

down.

NOTE: Do not use any type of tool when tightening

the cap. Hand tighten only (approximately 5 N·m or

44 in. lbs.) torque.

Fig. 4 Coolant Tank Pressure/Vent Cap

with a 68 percent antifreeze concentration, which

prevents freezing down to -67.7 deg. C (-90 deg. F). A

higher percentage will freeze at a warmer tempera-

ture. Also, a higher percentage of antifreeze can

cause the engine to overheat because the specific

heat of antifreeze is lower than that of water.

100 Percent Ethylene-Glycol—Should Not Be Used in

Chrysler Vehicles

Use of 100 percent ethylene-glycol will cause for-

mation of additive deposits in the system, as the cor-

rosion inhibitive additives in ethylene-glycol require

the presence of water to dissolve. The deposits act as

insulation, causing temperatures to rise to as high as

149 deg. C (300) deg. F). This temperature is hot

enough to melt plastic and soften solder. The

increased temperature can result in engine detona-

tion. In addition, 100 percent ethylene-glycol freezes

at 22 deg. C (-8 deg. F).

Propylene-glycol Formulations—Should Not Be Used in

Chrysler Vehicles

Propylene-glycol formulations do not meet

Chrysler coolant specifications.

It’s overall effec-

tive temperature range is smaller than that of ethyl-

ene-glycol. The freeze point of 50/50 propylene-glycol

and water is -32 deg. C (-26 deg. F). 5 deg. C higher

COOLANT PERFORMANCE

ETHYLENE-GLYCOL MIXTURES

The required ethylene-glycol (antifreeze) and water

mixture depends upon the climate and vehicle oper-

ating conditions. The recommended mixture of 50/50

ethylene-glycol and water will provide protection

against freezing to -37 deg. C (-35 deg. F). The anti-

freeze concentration

must always

be a minimum of

44 percent, year-round in all climates.

If percentage

is lower than 44 percent, engine parts may be

eroded by cavitation, and cooling system com-

ponents may be severely damaged by corrosion.

Maximum protection against freezing is provided

DESCRIPTION AND OPERATION (Continued)

than ethylene-glycol’s freeze point. The boiling point

(protection against summer boil-over) of propylene-

glycol is 125 deg. C (257 deg. F ) at 96.5 kPa (14 psi),

compared to 128 deg. C (263 deg. F) for ethylene-gly-

col. Use of propylene-glycol can result in boil-over or

freeze-up in Chrysler vehicles, which are designed for

ethylene-glycol. Propylene glycol also has poorer heat

transfer characteristics than ethylene glycol. This

can increase cylinder head temperatures under cer-

tain conditions.

Propylene-glycol/Ethylene-glycol Mixtures—Should Not Be

Used in Chrysler Vehicles

Propylene-glycol/ethylene-glycol

Mixtures

can

cause the destabilization of various corrosion inhibi-

tors, causing damage to the various cooling system

components. Also, once ethylene-glycol and propy-

lene-glycol based coolants are mixed in the vehicle,

conventional methods of determining freeze point will

not be accurate. Both the refractive index and spe-

cific gravity differ between ethylene glycol and propy-

lene glycol.

CAUTION: Richer antifreeze mixtures cannot be

measured with normal field equipment and can

cause problems associated with 100 percent ethyl-

ene-glycol.

COOLING SYSTEM

7-5

Fig. 5 Hose Clamp Tool

COOLING SYSTEM HOSES

Rubber hoses route coolant to and from the radia-

tor, water manifold and heater core. Models equipped

with air conditioning have a heater water control

(shut-off) valve. This is located in-line with the

heater core inlet and outlet hoses. It controls coolant

flow to the heater core when the air conditioning sys-

tem is in operation.

Radiator lower hoses are spring-reinforced to pre-

vent collapse from water pump suction at moderate

and high engine speeds.

WARNING: CONSTANT TENSION HOSE CLAMPS

ARE USED ON MOST COOLING SYSTEM HOSES.

WHEN REMOVING OR INSTALLING, USE ONLY

TOOLS DESIGNED FOR SERVICING THIS TYPE OF

CLAMP (Fig. 5). ALWAYS WEAR SAFETY GLASSES

WHEN SERVICING CONSTANT TENSION CLAMPS.

CAUTION: A number or letter is stamped into the

tongue of constant tension clamps (Fig. 6). If

replacement is necessary, use only an original

equipment clamp with matching number or letter.

Inspect the hoses at regular intervals. Replace

hoses that are cracked, feel brittle when squeezed, or

swell excessively when the system is pressurized.

Fig. 6 Clamp Number/Letter Location

For all vehicles: In areas where specific routing

clamps are not provided, be sure that hoses are posi-

tioned with sufficient clearance. Check clearance

from exhaust manifolds and pipe, fan blades, drive

belts and sway bars. Improperly positioned hoses can

be damaged, resulting in coolant loss and engine

overheating.

Ordinary worm gear type hose clamps (when

equipped) can be removed with a straight screw-

driver or a hex socket.

To prevent damage to

hoses or clamps, the hose clamps should be

tightened to 4 N·m (34 in. lbs.) torque. Do not

over tighten hose clamps.

When performing a hose inspection, inspect the

radiator lower hose for proper position and condition

of the internal spring.

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