part of the engine at appropriate temperature in
whatever condition the engine may be operated.
The cooling method is of the water-cooled, pres-
sure forced circulation type in which the water
pump pressurizes coolant and circulates it
throughout the engine. If the coolant temperature

exceeds the prescribed temperature, the thermo-
stat opens to circulate the coolant through the
radiator as well so that the heat absorbed by the
coolant may be radiated into the air. The water
pump is of the centrifugal type and is driven by
the drive belt from the crankshaft. The radiator is
the corrugated fin, down flow type.

SPECIAL TOOL

M1141000600279

ENGINE COOLING DIAGNOSIS

INTRODUCTION

M1141005300347

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 and fan assem-
blies. Possible faults include low coolant, contamina-
tion, belt loosening and component damage.

TROUBLESHOOTING STRATEGY

M1141005200340

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.

TOOL

TOOL NUMBER AND
NAME

SUPERSESSION

APPLICATION

MB991871
LLC changer

General service tool

Coolant refilling

MB991871

ENGINE COOLING DIAGNOSIS

ENGINE COOLING

14-3

SYMPTOM CHART

M1141005600393

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 being
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.

• 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. Retest the system.

Q: Is there still coolant leakage?

YES : Return to Step 1.
NO : The procedure is complete.

SYMPTOM

INSPECTION
PROCEDURE

REFERENCE
PAGE

Coolant leak

14-3