Ford Mustang (1999-2004) Service Manual: Engine Cooling (Diagnosis and Testing)

Special Tool(s)

Pressure Tester 014-R1072 or equivalent

73III Automotive Meter 105-R0057 or equivalent
Worldwide Diagnostic System (WDS) 418-F224, New Generation STAR (NGS) Tester 418-F052, or equivalent scan tool
Battery/Anti-Freeze Tester 014-R1060 or equivalent

Inspection and Verification

WARNING: Never remove the pressure relief cap while the engine is operating or when the cooling system is hot. Failure to follow these instructions can result in damage to the cooling system or engine or personal injury. To avoid having scalding hot coolant or steam blow out of the degas bottle when removing the pressure relief cap, wait until the engine is cooled, then wrap a thick cloth around the pressure relief cap and turn it slowly. Step back while the pressure is released from the cooling system. When you are sure all the pressure has been released, turn and remove the pressure relief cap (still with a cloth).

CAUTION: Check the coolant level, engine oil and transmission fluid, top off the coolant if needed. If there is engine coolant in the engine oil or transmission fluid, the cause must be corrected and oil/fluid changed or major component damage may occur.

1. Verify the customer's concern by operating the engine to duplicate the condition.

2. Inspect to determine if any of the following mechanical or electrical concerns apply.

Visual Inspection Chart

Mechanical

  • Leaks
  • Hoses
  • Hose clamps
  • Water gasket
  • Head gaskets
  • Intake manifold gasket
  • Coolant pump
  • Radiator
  • Degas bottle/coolant expansion tank
  • Heater core
  • Fan/fan clutch
  • Engine coolant temperature sensor (4.6L)
  • Cylinder head temperature sensor (3.8L)
  • Circuitry

3. If the inspection reveals an obvious concern that can be readily identified, repair as necessary.

4. CAUTION: Some vehicle cooling systems are filled with Motorcraft Premium Gold Engine Coolant VC-7-A (in Oregon VC-7-B) or equivalent meeting Ford specification WSS-M97B51-A1 (yellow color). Always fill the cooling system with the same coolant that is present in the system. Do not mix coolant types.

NOTE: The addition of Motorcraft Cooling System Stop Leak Pellets, VC-6, darkens Motorcraft Premium Gold Engine Coolant from yellow to golden tan.

Inspect the coolant condition.

1. Inspect the coolant color.

  • If Motorcraft Premium Gold Engine Coolant (yellow color) VC-7-A (in Oregon VC- 7-B) or equivalent meeting Ford specification WSS-M97B51-A1 has a clear or pale yellow color, this indicates higher water content than required.
  • Dark brown can indicate unauthorized stop leak may have been used. Use Motorcraft Cooling System Stop Leak Pellets VC-6 or equivalent meeting Ford specification ESE-M99B37-5 except as noted in ES-F6SE-19A511-AA only.
  • A light or reddish brown color indicates that rust may be present in the cooling system. Flush the system and refill with the correct mixture of water and engine coolant.
  • An iridescent sheen on top of the coolant can indicate a trace of oil is entering the system. For additional information on engine diagnosis, refer to Section.
  • A milky brown color may indicate that either engine oil or transmission fluid is entering the cooling system. If transmission fluid is suspected, the cause may be a leaky radiator. Pressure test the cooling system. For additional information, refer to component tests in this section. If engine oil is suspected the cause of the leak may be internal to the engine. For additional information, refer to Section.

2. If the engine coolant appearance is acceptable, test the engine coolant freezing point range with the battery and anti-freeze tester. The freezing point should be in the range - 40C to -20C (-50F to -10F). If the vehicle is driven in cold climates less than -32C (- 34F), it may be necessary to increase the coolant concentration to get adequate freeze protection.

  • Maximum coolant concentration is 60% coolant/40% water.
  • Minimum coolant concentration is 40% coolant/60% water.

3. Adjust coolant range and level, if necessary:

  • If coolant is low, add specified coolant mixture only.
  • If the engine coolant tests too weak, add straight engine coolant until the readings are within acceptable levels.
  • If the engine coolant tests strong, remove some of the engine coolant and add water until the readings are within acceptable levels.

5. If the concern remains after the inspection, determine the symptom(s) and GO to Symptom Chart

Symptom Chart

Condition Possible Sources Action
  • Loss of coolant
  • Radiator.
  • Coolant pump seal.
  • Radiator hoses.
  • Heater hoses.
  • Heater core.
  • Engine gaskets.
  • Degas bottle or coolant expansion tank.
  • Go To Pinpoint Test A .
  • The engine overheats
  • Thermostat.
  • Coolant pump.
  • Internal engine coolant leak.
  • Radiator.
  • Cooling fan.
  • Pressure relief cap or radiator cap
  • Go To Pinpoint Test B .
  • The engine does not reach normal operating temperature
  • Thermostat.
  • Go To Pinpoint Test C .

Pinpoint Tests

PINPOINT TEST A: LOSS OF COOLANT

Test Step Result / Action to Take
A1 CHECK THE ENGINE COOLANT LEVEL Yes

GO to A2 .

No

REFILL the engine coolant as necessary.

GO to A2 .

WARNING: Never remove the pressure relief cap while the engine is operating or when the cooling system is hot. Failure to follow these instructions can result in damage to the cooling system or engine or personal injury.

To avoid having scalding hot coolant or steam blow out of the degas bottle when removing the pressure relief cap, wait until the engine is cooled, then wrap a thick cloth around the pressure relief cap and turn it slowly. Step back while the pressure is released from the cooling system.

When you are sure all the pressure has been released, turn and remove the pressure relief cap (still with a cloth).

NOTE: Allow the engine to cool before checking the engine coolant level.

  • Key in OFF position.
  • Visually check the engine coolant level at the degas bottle or coolant expansion tank.
  • Is the engine coolant level within specification?
A2 CHECK THE PRESSURE RELIEF CAP Yes

GO to A3 .

No

INSTALL a new pressure relief cap/radiator cap. TEST the system for normal operation.

  • Carry out the Cap-3.8L or Cap-4.6L test. Go to Component Tests in this section.
  • Is pressure relief cap/radiator cap OK?
A3 CHECK THE ENGINE COOLANT FOR INTERNAL LEAK Yes

If engine oil is evident, REFER to Section. If transmission fluid is evident, REPAIR or INSTALL a new radiator as necessary.

No

GO to A4 .

  • Key in OFF position.
  • Inspect the engine coolant in degas bottle/coolant expansion tank for signs of transmission fluid or engine oil.
  • Is oil or transmission fluid evident in the coolant?
A4 CHECK THE ENGINE AND THE TRANSMISSION FOR COOLANT Yes

If coolant is in engine, REFER to Section. If coolant is in transmission, REPAIR or INSTALL a new radiator as necessary.

To repair the automatic transmission, REFER to Section.

No

GO to A5 .

  • Remove the oil level dipstick from the engine and the transmission.
  • Is coolant evident in the oil or transmission fluid?
A5 PRESSURE TEST THE ENGINE COOLING SYSTEM Yes

REPAIR or install new components. TEST the system for normal operation.

No

The cooling system is operational. GO to Symptom Chart .

  • Pressure test the engine cooling system. Go to Component Tests in this section.
  • Does the engine cooling system leak?

PINPOINT TEST B: THE ENGINE OVERHEATS

Test Step Result / Action to Take
B1 CHECK THE ENGINE COOLANT LEVEL Yes

GO to B2 .

No

REFILL the engine coolant at the degas bottle/coolant expansion tank. Go To Pinpoint Test A .

WARNING: Never remove the pressure relief cap while the engine is operating or when the cooling system is hot.

Failure to follow these instructions can result in damage to the cooling system or engine or personal injury. To avoid having scalding hot coolant or steam blow out of the degas bottle when removing the pressure relief cap, wait until the engine is cooled, then wrap a thick cloth around the pressure relief cap and turn it slowly. Step back while the pressure is released from the cooling system. When you are sure all the pressure has been released, turn and remove the pressure relief cap (still with a cloth).

NOTE: If the engine is hot, allow the engine to cool before proceeding.

  • Key in OFF position.
  • Check the engine coolant level at the degas bottle/coolant expansion tank.
  • Is the engine coolant OK?
B2 CHECK THE COOLANT CONDITION Yes

GO to B3 .

No

FLUSH the engine cooling system.

REFER to Engine and Radiator Flushing in this section. TEST the system for normal operation.

  • Check the coolant for dirt, rust or contamination.
  • Is the coolant condition OK?
B3 CHECK FOR AN AIRFLOW OBSTRUCTION Yes

REMOVE the obstruction. CLEAN the A/C condenser core and radiator. TEST the system for normal operation.

No

GO to B4

  • Inspect the A/C condenser core and radiator for obstructions such as leaves or dirt.
  • Is there an obstruction?
B4 CHECK THE WATER THERMOSTAT OPERATION Yes

INSTALL a new water thermostat. REFER to Thermostat-3.8L , Thermostat-4.6L(2V) or Thermostat-4.6L (4V) in this section.

TEST the system for normal operation.

No

GO to B5 .

  • Start the engine and allow the engine to run for ten minutes.
  • Feel the inlet and outlet heater water hoses and the underside of the upper radiator hose.
  • Are the upper radiator hose and the heater water hoses cold?
B5 CHECK THE COOLING FAN OPERATION Yes

For diagnosis and testing of the engine, REFER to Section.

No

INSTALL a new fan component as necessary. TEST the system for normal operation.

  • Carry out the cooling fan component tests. Go to Component Tests.
  • Is the cooling fan operation OK?

PINPOINT TEST C: THE ENGINE DOES NOT REACH NORMAL OPERATING TEMPERATURE

Test Step Result / Action to Take
C1 CHECK THE ENGINE TEMPERATURE Yes

INSTALL a new water thermostat. REFER to Thermostat-3.8L , Thermostat-4.6L(2V) or Thermostat-4.6L(4V) in this section. TEST the system for normal operation.

No

For diagnosis and testing of the engine coolant temperature gauge, REFER to Section.

  • Start the engine and allow the engine to idle for ten minutes.
  • Feel the inlet and heater water hoses and the underside of the upper radiator hose.
  • Are the upper radiator hose and the heater water hoses cold?

Component Tests

Pressure Test - 3.8L

WARNING: Never remove the pressure relief cap while the engine is operating or when the cooling system is hot. Failure to follow these instructions can result in damage to the cooling system or engine or personal injury. To avoid having scalding hot coolant or steam blow out of the degas bottle when removing the pressure relief cap, wait until the engine is cooled, then wrap a thick cloth around the pressure relief cap and turn it slowly. Step back while the pressure is released from the cooling system. When you are sure all the pressure has been released, turn and remove the pressure relief cap (still with a cloth).

1. Remove the radiator cap. Fill the radiator as needed. Fit the pressure tester to the radiator neck, using an aftermarket adapter.

2. CAUTION: Do not pressurize the cooling system beyond 110 kPa (16 psi).

Pump the cooling system to a maximum of 102 kPa (14.9 psi) and hold for 2 minutes. If the pressure drops within this time, inspect for leaks and repair as necessary.

Pressure Test - 4.6L

1. Turn the engine OFF.

2. WARNING: Never remove the pressure relief cap while the engine is operating or when the cooling system is hot. Failure to follow these instructions can result in damage to the cooling system or engine or personal injury. To avoid having scalding hot coolant or steam blow out of the degas bottle when removing the pressure relief cap, wait until the engine is cooled, then wrap a thick cloth around the pressure relief cap and turn it slowly. Step back while the pressure is released from the cooling system. When you are sure all the pressure has been released, turn and remove the pressure relief cap (still with a cloth).

Check the engine coolant level; refer to Cooling System Draining, Filling and Bleeding in this section.

3. Connect Radiator Heater Core Pressure Tester to the degas bottle nipple and vent hose. Install a pressure test pump to the quick-connect fitting of the test adapter.

4. CAUTION: Do not pressurize the cooling system beyond 152 kPa (22 psi).

NOTE: If the plunger of the pump is depressed too quickly, an erroneous pressure reading will result.

Slowly depress the plunger of the pressure test pump until the pressure gauge reading stops increasing and note the highest pressure reading obtained.

5. If the pressure relief cap does not hold pressure, remove and wash the pressure relief cap in clean water to dislodge all foreign particles from the gaskets. Check the sealing surface in the filler neck.

6. If 110 kPa (16 psi) cannot be reached, install a new pressure relief cap. If more than 124 kPa (18 psi) shows on gauge, install a new pressure relief cap.

7. CAUTION: If the pressure drops, check for leaks at the engine-to-heater core hoses, engine-to-radiator hoses, water valve hose (if applicable), oil cooler return tube gasket (6N789), radiator and heater core or other system components and connections. Any leaks which are found must be corrected and the system rechecked.

Pressurize the engine cooling system as described in Step 4 (using a pressure relief cap that operates within the specified upper and lower pressure limits). Observe the gauge reading for approximately two minutes; refer to General Specifications. Pressure should not drop during this time.

8. Release the system pressure by loosening the pressure relief cap. Check the engine coolant level and replenish, if necessary, with the correct engine coolant mixture; refer to Cooling System Draining, Filling and Bleeding in this section.

Cap - 3.8L

1. Inspect the radiator cap and seals for damage or deterioration. Install a new radiator cap if necessary.

2. Fit the radiator cap to Radiator/Heater Core Pressure Tester Kit, using the aftermarket adapter.

3. NOTE: If the plunger of the pressure tester is depressed too fast, an incorrect pressure reading will result.

Slowly pump the pressure tester until the pressure gauge stops increasing and note the highest pressure reading. Release pressure and repeat the test. Install a new radiator cap if the pressure is not 99.3-121.4 kPa (14.4-17.6 psi)

Cap - 4.6L

WARNING: Never remove the pressure relief cap while the engine is operating or when the cooling system is hot. Failure to follow these instructions can result in damage to the cooling system or engine or personal injury. To avoid having scalding hot coolant or steam blow out of the degas bottle when removing the pressure relief cap, wait until the engine is cooled, then wrap a thick cloth around the pressure relief cap and turn it slowly. Step back while the pressure is released from the cooling system. When you are sure all the pressure has been released, turn and remove the pressure relief cap (still with a cloth).

1. Remove the pressure relief cap from the degas bottle.

2. Follow the instructions from the pressure tester.

3. NOTE: If the plunger of the pump is depressed too quickly, an erroneous pressure reading will result.

Slowly depress the plunger of the pressure test pump until the pressure gauge reading stops increasing and note the highest pressure reading obtained.

4. If the pressure test gauge readings are not within specifications, install a new pressure relief cap. If the pressure test gauge readings are within specifications, carry out the cooling system Pressure Test.

Thermostat - Water

A new water thermostat should be installed only after the following electrical and mechanical tests have been carried out.

Thermostat - Electrical Test

CAUTION: Always vent the exhaust to the outside when carrying out this test.

NOTE: The electrical thermostat test is most accurate if carried out at less than 37.8C (100F) ambient air. This test may be carried out with or without the hood open and with the engine warm or cold.

1. Check the engine coolant level. Fill as needed.

2. With the ignition OFF, remove the engine coolant temperature (ECT) (4.6L) or cylinder head temperature (CHT) (3.8L) sensor harness connector and attach ECT (4.6L) or CHT (3.8L) Sensor "T" Cable as a jumper between the powertrain control module (PCM) (12A650) and the ECT (4.6L) or CHT (3.8L) sensor. Attach the 73III Automotive Meter to the ECT (4.6L) or CHT (3.8L) Sensor "T" Cable. Voltage values (0-5 V) may now be monitored while the sensor retains its connection to the wiring harness.

An appropriate diagnostic tool may be used to monitor the ECT on vehicles equipped with data link connector (DLC).

3. NOTE: Running this test with the vehicle in gear or with the A/C compressor clutch engaged (running) will cause incorrect diagnosis.

Place the transmission in PARK (P) or NEUTRAL (N).

4. Start the engine and allow the engine to idle throughout this test. Allow the engine to run for 2 minutes, then record the ECT (4.6L) or CHT (3.8L) voltage. Record the ECT (4.6L) or CHT (3.8L) voltage every 60 seconds. When the ECT (4.6L) or CHT (3.8L) voltage trend changes direction or only changes slightly (0.03 volts or less) from the previous reading, record this as the thermostat opening voltage. Use the voltage and corresponding coolant temperature chart listed below for 4.6L engines only.

Coolant Temperature C (F)

ECT (Volts)
22 (71) 3.00
43 (109) 2.01
71 (159) 1.01
82 (180) 0.75
91 (195) 0.059
97 (206) 0.050
105 (221) 0.040

5. If the thermostat opening voltage is greater than 0.75 volts and less than 82C (180F), install a new water thermostat.

6. If the thermostat opening voltage is less than 0.75 volts and greater than 82C (180F), the water thermostat is good and a new water thermostat should not be installed. GO to Symptom Chart for further instructions.

Thermostat - Mechanical Test

1. Remove the water thermostat.

2. Check the water thermostat for seating. Hold the water thermostat up to a lighted background.

Leakage of light around the thermostat valve at room temperature indicates that a new water thermostat should be installed. Some water thermostats have a small leakage notch at one location on the perimeter of the thermostat valve, which is considered normal.

3. Immerse the water thermostat in a boiling coolant and water mixture.

4. See the General Specifications chart for water thermostat opening temperatures.

Radiator Leak Test, Removed From the Vehicle

CAUTION: Never leak test an aluminum radiator in the same water that copper/brass radiators are tested in. Flux and caustic cleaners may be present in the cleaning tank and they will damage aluminum radiators.

NOTE: Always install plugs in the oil cooler fittings before leak-testing or cleaning any radiator.

NOTE: Clean the radiator before leak-testing to avoid contamination of tank.

1. Leak-test the radiator in clean water with 138 kPa (20 psi) air pressure.

Fan - Electric Test

Refer to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.

    Engine Cooling (Description and Operation)
    CAUTION: Vehicle cooling systems are filled with Motorcraft Premium Gold Engine Coolant VC-7-A (in Oregon VC-7-B) or equivalent meeting Ford specification WSS-M97B51-A1 (yellow color). Always fill t ...

    Cooling System Draining, Filling and Bleeding
    Material Item Specification Motorcraft Premium Gold Engine Coolant VC-7-A (in Oregon VC-7-B) (yellow color) WSS-M97B51- A1 Draining WARNING: Never remove the pressure relief ...

    Other materials:

    Output Shaft
    Special Tool(s) Remover, Drive Pinion Bearing Cone 205-D002 (D79L-4621-A) or equivalent Installer, Drive Pinion Bearing Cone 205-011 (T57L-4621-B) ...

    Trim Panel - Package Tray
    Special Tool(s) Torx Bit, Safety Belt Bolt 501-010 (T77L-2100-A) Removal and Installation 1. Remove the screw and the coat hook. 2. NOTE: Inspect the shoulder safety belt guide cover for damage. If the shoulder safety belt guide cover is d ...

    Removal
    Both mounts 1. Disconnect the battery ground cable. For additional information, refer to Section. 2. Remove the coolant bypass tube. For additional information, refer to Section. 3. Rotate the drive belt tensioner clockwise and detach the drive belt from th ...