2010-2016 JEEP WRANGLER
SERVICE AND REPAIR MANUAL
2013 ENGINE
Cooling System - Wrangler
DESCRIPTION
DESCRIPTION
The cooling system regulates engine operating temperature. It allows the engine to reach normal operating
temperature as quickly as possible, maintains normal operating temperature and prevents overheating.
The cooling system also provides a means of heating the passenger compartment and cooling the automatic
transmission fluid. The cooling system is pressurized and uses a centrifugal water pump to circulate coolant
throughout the system.
COOLING SYSTEM COMPONENTS
The cooling system consists of:
Charge Air Cooler (Diesel engine)
2 Speed Electric Cooling Fan
Aluminum-core radiator with plastic side tanks
Coolant recovery container
Water pump
Combination A/C condenser/transmission oil cooler (automatic transmission)
Thermostat
Hoses and hose clamps
OPERATION
OPERATION
When engine is cold the thermostat is closed. The cooling system has no flow through the radiator. The
coolant flows through the engine, water pump, and heater.
When engine is warm, the thermostat is full open. The coolant flows through the engine, radiator, heater,
and water pump.
On the diesel engine coolant flows through the engine, radiator, heater, and water pump.
As coolant expands, some coolant will move to the coolant recovery container. Once the coolant cools,
the coolant from the coolant recovery container will move back to the radiator. (Gas engine only)
DIAGNOSIS AND TESTING
PRELIMINARY CHECKS
2013 ENGINE Cooling System - Wrangler 2013 ENGINE Cooling System - Wrangler
ENGINE COOLING SYSTEM OVERHEATING
Establish what driving conditions caused the complaint. Abnormal loads on the cooling system such as the
following may be the cause:
Prolonged idle
Very high ambient temperature
Overloaded Truck
Slow traffic
Traffic jams
High speed or steep grades
Snow Plow restricting airflow through cooling module
Debris on front of the grill or the cooling module that is restricting airflow
Driving techniques that avoid overheating are:
Idle with A/C off when temperature gauge is at end of normal range.
Increasing engine speed up to 2000 RPM with transmission in park or neutral for more airflow is
recommended.
If equipped with a snow plow. Activate the snow plow mode.
TRAILER TOWING:
Consult Trailer Towing section of the Owner's Manual. Do not exceed the limits.
RECENT SERVICE OR ACCIDENT REPAIR:
Determine if any recent service has been performed on vehicle that may affect the cooling system. This may be:
Engine adjustments (incorrect timing)
Slipping engine accessory drive belt(s)
Brakes (possibly dragging)
Changed parts. Incorrect water pump or pump rotating in wrong direction due to belt not correctly routed
Reconditioned radiator or cooling system refilling (possibly under filled or air trapped in system).
Service to electrically controlled viscous fan clutch
These charts are to be used as a quick-reference only.
COOLING SYSTEM DIAGNOSIS CHART
NOTE: If investigation reveals none of the previous items as a cause for an engine
overheating complaint, refer to the COOLING SYSTEM DIAGNOSIS CHART .
CONDITION POSSIBLE CAUSES CORRECTION
2013 ENGINE Cooling System - Wrangler
TEMPERATURE GAUGE
READS LOW
NOTE:
Information on dash cluster is
displayed based on broadcast
data from PCM. DTC will be set
for engine sensor circuit issues.
1. Vehicle is equipped with a
heavy duty cooling system.
1. None. System operating
normally.
2. Thermostat stuck open 2. Inspect and test thermostat. Refer
to THERMOSTAT, DIAGNOSIS
AND TESTING .
3. Coolant level low. 3. Fill cooling system. Refer to
STANDARD PROCEDURE .
4. Temperature gauge not
functioning correctly.
4. Check cluster. Refer to
DIAGNOSIS AND TESTING .
5. Engine sensor stuck in range 5. Monitor sensor with scan tool to
verify sensor reading changes with
increasing temperature.
6. Engine sensor failed out of
range.
6. A DTC will be set.
7. Electronically Controlled
Viscous Fan Drive/mechanical
viscous fan not operating
properly.
7. Check Electronically Controlled
Viscous Fan Drive.
TEMPERATURE GAUGE
READS HIGH. COOLANT MAY
OR MAY NOT BE LEAKING
FROM SYSTEM
NOTE:
Temperature information
displayed on dash cluster and
EVIC are based on broadcast
data from PCM. If engine
temperatures exceed
thresholds, power is reduced
and a message of 'Oil Temp
High - Speed May be Reduced'
is displayed on the EVIC.
NOTE:
Beginning in MY2010, a 200 F
thermostat is used in the Ram
2500/3500 pickup with the
Cummins Turbo Diesel. It is
normal for the coolant
temperature gauge to read
higher than in previous model
1. Vehicle overloaded, high
ambient (outside) temperatures
with A/C turned on, stop and go
driving or prolonged operation at
idle speeds.
1. Temporary condition, repair not
required. Notify customer of
vehicle operation instructions
located in Owner's Manual.
2013 ENGINE Cooling System - Wrangler
years.
2. Electronically-controlled
viscous fan clutch not
functioning correctly.
2. Troubleshoot and if necessary
repair the electronic viscous fan
clutch.
3. Temperature gauge not
functioning correctly.
3. Check cluster. Refer to
DIAGNOSIS AND TESTING .
4. Air trapped in cooling system 4. Drain and refill cooling system.
Refer to STANDARD
PROCEDURE .
5. Radiator cap faulty. 5. Replace radiator cap.
6. Plugged A/C or radiator
cooling fins.
6. Clean all debris away from A/C
and radiator cooling fins.
7. Coolant mixture incorrect. 7. Drain cooling system and refill
with correct mixture. Refer to
STANDARD PROCEDURE .
8. Thermostat stuck shut. 8. Inspect and test thermostat Refer
to THERMOSTAT, DIAGNOSIS
AND TESTING .
9. Bug screen or winter front
being used.
9. Remove bug screen or winter
front.
10. Electronically controlled
viscous fan drive not operating
properly.
10. Check viscous fan.
11. Cylinder head gasket leaking. 11. Check for leaking head gaskets.
Refer to DIAGNOSIS AND
TESTING .
12. Heater core leaking. 12. Replace heater core. Refer to
CORE, HEATER, REMOVAL .
13. Cooling system hoses
leaking.
13. Tighten clamps or Replace
hoses.
14. Brakes dragging. 14. Check brakes. Refer to
DIAGNOSIS AND TESTING .
15. Accessory drive belt. 15. Inspect and replace as
necessary. Refer to BELT,
SERPENTINE, DIAGNOSIS
AND TESTING .
16. Water Pump. 16. Inspect and replace as
necessary.
17. Engine sensor stuck in range. 17. Monitor sensor with scan tool
to verify sensor reading changes
increase in temperature.
18. Temperature sensor failed -
Too High
18. Clear the existing overheat
fault. Drive the vehicle until
thermostat opens. Verify that fault
code does not return and coolant
2013 ENGINE Cooling System - Wrangler
does not reach threshold of 230
degrees F.
TEMPERATURE GAUGE
READING INCONSISTENT
(ERRATIC, CYCLES OR
FLUCTUATES)
NOTE:
Information on dash cluster is
displayed based on broadcast
data from PCM. DTC will be set
for engine sensor circuit issues.
1. Heavy duty cooling system,
extreme cold ambient (outside)
temperature or heater blower
motor in high position.
1. None. System operating
normally.
2. Temperature gauge or sensor
defective.
2. Check cluster or engine coolant
temp sensor. Refer to DIAGNOSIS
AND TESTING .
3. Temporary heavy usage or
load.
3. None. Normal condition.
4. Air trapped in cooling system. 4. Fill cooling system. Refer to
STANDARD PROCEDURE .
5. Water pump. 5. Replace water pump.
6. Air leak on suction side of
water pump.
6. Check for leak. Refer to
DIAGNOSIS AND TESTING .
RADIATOR CAP LEAKING
STEAM AND OR COOLANT
INTO RESERVOIR BOTTLE.
(TEMPERATURE GAUGE MAY
READ HIGH)
1. Radiator cap defective. 1. Replace radiator cap.
2. Radiator neck surface
damaged.
2. Replace radiator. Refer to
RADIATOR, ENGINE
COOLING, INSTALLATION .
HOSE OR HOSES COLLAPSE
WHEN ENGINE IS COOLING.
1. Vacuum created in cooling
system on engine cool-down is
not being relieved through
coolant reservoir/overflow
system.
1. Replace radiator cap, check vent
hose between radiator and reservoir
bottle for blockage also check
reservoir bottle vent for blockage.
NOISY FAN 1. Fan blade(s) loose, damaged. 1. Replace fan blade assembly.
2. Electronically controlled
viscous fan drive/mechanical
viscous fan.
2. None. Normal condition.
3. Fan blades striking
surrounding objects.
3. Locate contact point and repair
as necessary.
4. Electronically controlled
viscous fan drive/mechanical
viscous fan bearing concern.
4. Check viscous fan drive.
5. Electronically controlled
viscous fan/mechanical viscous
fan stuck on.
5. Check viscous fan drive.
6. Obstructed air flow through
radiator.
6. Remove obstruction.
2013 ENGINE Cooling System - Wrangler
LEAK TESTING
ULTRAVIOLET LIGHT METHOD
INADEQUATE AIR
CONDITIONER
PERFORMANCE (COOLING
SYSTEM SUSPECTED)
1. Radiator and/or A/C condenser
air flow obstructed.
1. Remove obstruction and/or
clean.
2. Electronically controlled
viscous fan drive/mechanical
viscous fan not working.
2. Check viscous fan drive.
3. Air seals around radiator
damaged or missing.
3. Inspect air seals, repair or replace
as necessary.
INADEQUATE HEATER
PERFORMANCE. GAUGE
MAY OR MAY NOT READ
LOW.
1. Heavy duty cooling system,
and cooler ambient temperatures.
1. None. Normal condition.
2. Obstruction in heater hoses. 2. Remove hoses, remove
obstruction.
3. Electronically controlled
viscous fan/mechanical viscous
fan stuck on.
Check viscous fan drive.
4. Water pump damaged. 4. Replace water pump.
HEAT ODOR 1. Damaged or missing exhaust
system heat shields.
1. Repair or replace damaged or
missing exhaust system heat
shields. Refer to SHIELD, HEAT,
DESCRIPTION .
2. Electronically controlled
viscous fan drive//mechanical
viscous fan damaged.
2. Check viscous fan drive.
2013 ENGINE Cooling System - Wrangler
Fig. 1: Leak Detection Using Black Light
Courtesy of CHRYSLER GROUP, LLC
All Jeep models have a leak detection additive added to the cooling system before they leave the factory. The
additive is highly visible under ultraviolet light (black light). If the factory original coolant has been drained,
pour one ounce of additive into the cooling system. The additive is available through the parts department.
Place the heater control unit in HEAT position. Start and operate the engine until the radiator upper hose is
warm to the touch. Aim the commercially available black light tool at the components to be checked. If leaks
are present, the black light will cause the additive to glow a bright green color.
The black light can be used along with a pressure tester to determine if any external leaks exist.
PRESSURE TESTER METHOD
Fig. 2: Pressurizing System
Courtesy of CHRYSLER GROUP, LLC
The engine should be at the normal operating temperature. Recheck the system cold if the cause of coolant loss
is not located during warm engine examination.
Carefully remove the radiator pressure cap from the filler neck and check the coolant level. Push down on the
cap to disengage it from the stop tabs. Wipe the inner part of the filler neck and examine the lower inside
sealing seat for nicks, cracks, paint, dirt and solder residue. Inspect the reserve/overflow tank tube for internal
obstructions. Insert a wire through the tube to be sure it is not obstructed.
1 - TYPICAL BLACK LIGHT TOOL
1 - TYPICAL COOLING SYSTEM PRESSURE TESTER
WARNING: Hot, pressurized coolant can cause injury by scalding.
2013 ENGINE Cooling System - Wrangler
Inspect the cams on the outside part of the filler neck. If the cams are bent, seating of pressure cap valve and
tester seal will be affected. Replace cap if cams are bent.
Attach pressure tester (special tool #7700, Tester, Cooling System) (or an equivalent) to the radiator filler neck.
Operate the tester pump to apply 124 kPa (18 psi) pressure to the system. If the hoses enlarge excessively or
bulge while testing, replace as necessary. Observe the gauge pointer and determine the condition of the cooling
system according to the following criteria:
Holds Steady: If the pointer remains steady for two minutes, there are no serious coolant leaks in the
system. However, there could be an internal leak that does not appear with normal system test pressure.
Inspect for interior leakage or do the Internal Leakage Test. Do this if it is certain that coolant is being
lost and no leaks can be detected.
Drops Slowly: Shows a small leak or seepage is occurring. Examine all connections for seepage or slight
leakage with a flashlight. Inspect the radiator, hoses, gasket edges and heater. Seal any small leak holes
with a Sealer Lubricant or equivalent. Repair leak holes and reinspect the system with pressure applied.
Drops Quickly: Shows that a serious leakage is occurring. Examine the system for serious external
leakage. If no leaks are visible, inspect for internal leakage. Large radiator leak holes should be repaired
by a reputable radiator repair shop.
INTERNAL LEAKAGE INSPECTION
Remove the engine oil pan drain plug and drain a small amount of engine oil. Coolant, being heavier than
engine oil, will drain first. Another way of testing is to operate the engine and check for water globules on the
engine oil dipstick. Also inspect the automatic transmission oil dipstick for water globules. Inspect the
automatic transmission fluid cooler for leakage. Operate the engine without the pressure cap on the radiator
until thermostat opens.
Attach a pressure tester to the filler neck. If pressure builds up quickly, a leak exists as a result of a faulty
cylinder head gasket or crack in the engine. Repair as necessary.
If there is no immediate pressure increase, pump the pressure tester until the indicated pressure is within the
system range. Vibration of the gauge pointer indicates compression or combustion leakage into the cooling
system.
WARNING: DO NOT ALLOW PRESSURE TO EXCEED 124 KPA (18 PSI). TURN THE
ENGINE OFF. TO RELEASE THE PRESSURE, ROCK THE TESTER FROM
SIDE TO SIDE. WHEN REMOVING THE TESTER, DO NOT TURN THE
TESTER MORE THAN 1/2 TURN IF THE SYSTEM IS UNDER PRESSURE.
WARNING: Do not disconnect the spark plug wires while the engine is operating.
CAUTION: Do not operate the engine with a spark plug shorted for more than a
minute. The catalytic converter may be damaged.
2013 ENGINE Cooling System - Wrangler
Isolate the compression leak by shorting each spark plug to the cylinder block. The gauge pointer should stop or
decrease vibration when spark plug for leaking cylinder is shorted. This happens because of the absence of
combustion pressure.
COMBUSTION LEAKAGE TEST (WITHOUT PRESSURE TESTER)
DO NOT WASTE reusable coolant. If the solution is clean, drain the coolant into a clean container for reuse.
Remove thermostat. Refer to THERMOSTAT, REMOVAL .
Remove accessory drive belt. Refer to BELT, SERPENTINE, REMOVAL .
Add coolant to the radiator to bring the level to within 6.3 mm (1/4 in) of the top of the thermostat housing.
Start the engine and accelerate rapidly three times (to approximately 3000 RPM) while observing the coolant. If
internal engine combustion gases are leaking into the cooling system, bubbles will appear in the coolant. If
bubbles do not appear, there is no internal combustion gas leakage.
STANDARD PROCEDURE
CLEANING/REVERSE FLUSHING
Reverse flushing of the cooling system is the forcing of water through the cooling system. This is done using air
pressure in the opposite direction of normal coolant flow. It is usually only necessary with very dirty systems
with evidence of partial plugging.
CHEMICAL CLEANING
If visual inspection indicates the formation of sludge or scaly deposits, use a radiator cleaner, Mopar® Radiator
Kleen or equivalent, before flushing. This will soften scale and other deposits and aid the flushing operation.
WARNING: Do not remove the cylinder block drain plugs or loosen the radiator
draincock with the system hot and under pressure. Serious burns from
coolant can occur.
CAUTION: Avoid overheating. Do not operate the engine for an excessive period of
time. Open the draincock immediately after the test to eliminate boil over
of coolant.
CAUTION: The cooling system normally operates at 97 - 110 kPa (14 -16 psi)
pressure. Exceeding this pressure may damage the radiator or hoses.
CAUTION: Be sure instructions on the container are followed.
2013 ENGINE Cooling System - Wrangler
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Description
The 2011-2012 Jeep Wrangler Service & Repair Manual is a comprehensive guide for maintaining and repairing your Jeep Wrangler during the 2011-2012 model years. Whether you are a professional mechanic or a DIY enthusiast, this manual provides detailed instructions and clear diagrams to help you complete any repair or maintenance task with confidence.
- Comprehensive information on engine, transmission, electrical system, suspension, steering, brakes, and more
- Covers all Jeep Wrangler models released between 2011 and 2012
- Step-by-step instructions for each repair or maintenance procedure
- Easy-to-follow diagrams for a clear understanding of components and systems
- Specifications, troubleshooting guides, and expert tips for optimal performance and longevity
- Authored by Jeep experts to ensure accurate and reliable information
- Enables you to perform repairs and maintenance on your own, saving time and money
Whether you need to replace a part, carry out routine maintenance, or address a more complex repair, the 2011-2012 Jeep Wrangler Service & Repair Manual is your essential resource. With this manual at hand, you can confidently keep your Jeep Wrangler in peak condition for years to come.
