Mitsubishi Eclipse. Manual - part 650

ENGINE COOLING DIAGNOSIS

TSB Revision

COOLING SYSTEM

14-3

ENGINE COOLING DIAGNOSIS

INTRODUCTION

M1141005300217

The system cools the engine so that it does not over-
heat and maintains the engine at an optimum tem-
perature. The system components are the radiator, 
water pump, thermostat, condenser fan assembly. 
Possible faults include low coolant, contamination, 
belt loosening and component damage.

TROUBLESHOOTING STRATEGY

M1141005200210

Use these steps to plan your diagnostic strategy. If 
you follow them carefully, you will be sure to find 
most of the engine cooling faults.
1. Gather information from the customer.

2. Verify that the condition described by the 

customer exists.

3. Find and repair the malfunction by following the 

SYMPTOM CHART.

4. Verify that the malfunction is eliminated.

SYMPTOM CHART

M1141005600207

SYMPTOMS

INSPECTION 
PROCEDURE

REFERENCE 
PAGE

Coolant Leak

1

P.14-4

Engine Overheating

2

P.14-4

Radiator Fan and Condenser Fan do not Operate

3

P.14-6

Radiator Fan and Condenser Fan do not Change Speed or Stop 

4

P.14-14

Radiator Fan does not Operate

5

P.14-16

Condenser Fan does not Operate

6

P.14-17

ENGINE COOLING DIAGNOSIS

TSB Revision

COOLING SYSTEM

14-4

SYMPTOM PROCEDURES

INSPECTION PROCEDURE 1: Coolant Leak

DIAGNOSIS

STEP 1. Check for coolant leaks.

WARNING

When pressure testing the cooling system, slowly 
release cooling system pressure to avoid getting 
burned by hot coolant.

CAUTION

• Be sure to completely clean away any moisture from 

the places checked.

• When the tester is removed, be careful not to spill any 

coolant from it.

• When installing and removing the tester and when test-

ing, be careful not to deform the filler neck of the radia-
tor.

Check that the coolant level is up to the filler neck. Install a radi-
ator tester and apply 160 kPa (23 psi) pressure, and then check 
for leakage from the radiator hose or connections.
Q: Is leakage present from the radiator hose or 

connections?
YES : Repair or replace the appropriate part, then go to 

Step 2.

NO :  There is no action to be taken.

STEP 2. Check symptoms.
Q: Can the symptom be reproduced?

YES : Return to Step 1.
NO :  This diagnosis is complete.

INSPECTION PROCEDURE 2: Engine Overheating

DIAGNOSIS

STEP 1. Remove the radiator cap and check for coolant 
contamination.
Q: Is the coolant contaminated with rust and oil?

YES : Replace it. Refer to GROUP 00, Maintenance Service 

− Engine Coolant (Change) 

P.00-58

.

NO :  There is no action to be taken, then go to Step 2.

ACX01844 AB

CAP ADAPTER

ADAPTER

ENGINE COOLING DIAGNOSIS

TSB Revision

COOLING SYSTEM

14-5

STEP 2. Check the radiator cap valve opening pressure.
NOTE:  Be sure that the cap is clean before testing. Rust or 
other foreign material on the cap seal will cause an improper 
reading.
(1) Use a cap adapter to attach the cap to the tester.
(2) Increase the pressure until the gauge indicator stops 

moving.

Minimum limit: 83 kPa (12 psi)
Standard value: 93 

− 123 kPa (14 − 18 psi)

Q: Does the reading remain at or above the minimum limit?

YES : Go to Step 3.
NO :  Replace the radiator cap. Then go to Step 5.

STEP 3. Check thermostat operation.
Refer to 

P.14-24

.

Q: Is the thermostat operate correctly?

YES : Go to Step 4.
NO :  Replace the thermostat, then go to Step 5.

STEP 4. Check the drive belt for slippage or damage.
Refer to GROUP 00, Maintenance Service 

− Drive Belts 

(Check Condition) 

P.00-46

.

Q: Is the drive belt loose or damaged?

YES : Adjust or replace the drive belt, then go to Step 5.
NO :  There is no action to be taken.

STEP 5. Check symptoms.
Check the coolant temperature gauge.
Q: Is the coolant temperature abnormally high?

YES : Return to Step 2.
NO :  This diagnosis is complete.

ACX01845 AB

CAP ADAPTER

ENGINE COOLING DIAGNOSIS

TSB Revision

COOLING SYSTEM

14-6

INSPECTION PROCEDURE 3: Radiator Fan and Condenser Fan do not Operate

AC102870

Radiator Fan and Condenser Driver Circuit

<2.4L ENGINE>

AB