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2008 - MX-5 - Engine

NO.17 COOLING SYSTEM CONCERNS-OVERHEATING [LF]



17

COOLING SYSTEM CONCERNS-OVERHEATING

DESCRIPTION

Engine runs at higher than normal temperature/overheats.

POSSIBLE CAUSE

  • Improper coolant level

  • Blown fuses

  • Coolant leakage

  • Excessive A/C system pressure

  • A/C system operation is improper

  • Improper water/anti‐freeze mixture

  • Fans reverse rotation

  • Poor radiator condition

  • Thermostat malfunction

  • Radiator hoses damage

  • Improper or damaged radiator cap

  • Cooling fan is inoperative.

  • Coolant overflow system malfunction

  • Improper tension of drive belt

  • Drive belt damage


Diagnostic procedure

STEP

INSPECTION

RESULTS

ACTION

1

Inspect the following:

  • Engine coolant level

  • Coolant leakage

  • Water and anti‐freeze mixture

  • Radiator condition

  • Collapsed or restricted radiator hoses

  • Radiator pressure cap

  • Overflow system

  • Fan rotational direction

  • Fuses

Are all items normal?

Yes

Go to the next step.

No

Service if necessary.

Repeat Step 1.

2

Connect the M-MDS to the DLC-2.

Turn the ignition switch to the ON position (Engine off).

Retrieve any DTCs.

Are there any DTCs displayed?

Yes

DTC is displayed:

Go to the appropriate DTC inspection.

(See DTC TABLE [LF].)

No

No DTC is displayed:

Go to the next step.

3

Start the engine and idle it.

Turn the A/C switch on and set blower fan to any speed.

Does the A/C compressor engage?

Yes

Go to Step 5.

No

Inspect for the following and repair or replace if necessary:

  • Refrigerant charging amount

  • Open circuit in wiring harness between A/C relay and PCM terminal 1I

  • Seized A/C magnetic clutch

  • A/C magnetic clutch malfunction

If all items are normal, go to the next step.

4

Connect the M-MDS to DLC-2.

Access AC_REQ PID.

Start the engine and idle it.

Turn the A/C switch and fan switch on.

Does AC_REQ PID read on?

Yes

Go to the next step.

No

Inspect the following:

  • Refrigerant pressure switch operation

  • The A/C switch is stuck open.

  • Open or short circuit between refrigerant pressure switch and PCM terminal 1AU

  • Open circuit of blower motor fan switch and resistor (if blower motor does not operate)

  • The evaporator temperature sensor and A/C amplifier

5

Inspect cooling fan control system operation.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [LF].)

Does the cooling fan control system function properly?

Yes

Go to the next step.

No

Repair or replace the malfunctioning part.

6

Is the drive belt normal?

Yes

Go to the next step.

No

Replace the drive belt.

7

Is there leakage around the heater unit in passenger compartment?

Yes

Inspect and service heater for leakage.

No

Go to the next step.

8

Is there leakage at the coolant hoses and/or radiator?

Yes

Replace the malfunctioning part.

No

Go to the next step.

9

Cool down the engine.

Remove thermostat and inspect operation.

(See THERMOSTAT REMOVAL/INSTALLATION [LF].)

(See THERMOSTAT INSPECTION [LF].)

Is thermostat normal?

Yes

The engine coolant temperature and thermostat are normal, inspect engine block for leakage or blockage.

No

Access ECT PID.

Inspect for both ECT PID and temperature gauge readings.

If temperature gauge on instrument cluster indicates normal range but ECT PID is not same as temperature gauge reading, inspect ECT sensor.

If temperature gauge on instrument cluster indicates overheating but ECT PID is normal, inspect temperature gauge and heat gauge unit.

10

  • Verify test results.

    • If normal, return to diagnostic index to service any additional symptoms.

      (See SYMPTOM DIAGNOSTIC INDEX [LF].)

    • If malfunction remains, inspect related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis.

      • If vehicle is repaired, troubleshooting completed.

      • If vehicle is not repaired or additional diagnostic information is not available, replace the PCM.

        (See PCM REMOVAL/INSTALLATION [LF].)




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