Ford F150 Pickup. Instruction - part 996

dislodge all foreign particles from the gaskets. Check the sealing surface in the filler neck. 

6. If 89 kPa (13 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. 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. For additional information, refer to 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. For additional information, refer to 
COOLING SYSTEM DRAINING, FILLING & BLEEDING .  

CAP - PRESSURE RELIEF 

1. Inspect the pressure relief cap and seals for damage or deterioration. Install a new pressure relief cap if 

necessary.  

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

3. Slowly pump the pressure tester until the pressure gauge stops increasing and note the highest pressure 

reading. Release pressure and repeat test. Install a new pressure relief cap if the pressure is not 99.3-121.4 
kPa (14.4-17.6 psi).  

THERMOSTAT 

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

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.

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 has 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 plunger of the pressure tester is depressed too fast, an incorrect 
pressure reading will result.

 

2003 Ford Pickup F150 

2003 ENGINE Engine Cooling - F150 Pickup

  

carried out. 

THERMOSTAT-ELECTRICAL TEST 

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

2. With the key OFF, remove the engine coolant temperature (ECT) sensor harness connector and attach 

ECT Sensor "T" Cable as a jumper between the powertrain control module (PCM) (12A650) and the ECT 
Sensor. Attach 73III Automotive Meter to the ECT Sensor "T" Cable. Voltage values (0 to 5 V) may now 
be monitored while the sensor retains its connection to the wiring harness. 

A diagnostic tool may be used to monitor the ECT on vehicles equipped with Data Link Connector 
(DLC). 

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

4. Start the engine and allow to idle throughout this test. Allow the engine to run for two minutes, then 

record the ECT voltage. Record the ECT voltage every 60 seconds. When the ECT voltage trend changes 
direction or only changes slightly (0.03 volt or less) from the previous reading, record this as the 
thermostat opening voltage. Use the voltage and corresponding coolant temperature chart listed below. 

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

NOTE:

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

NOTE:

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

 

2003 Ford Pickup F150 

2003 ENGINE Engine Cooling - F150 Pickup

  

Fig. 14: ECT Voltage & Corresponding Coolant Temperature Chart 
Courtesy of FORD MOTOR CO. 

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

thermostat.  

6. If the thermostat opening voltage is less than 0.75 volt and greater than 82°C (180°F), the water 

thermostat is good and should not be replaced. GO to SYMPTOM CHART .  

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 the water thermostat should be 
replaced. Some water thermostats have a small leakage notch at one location on the perimeter of the 
thermostat valve, which is considered normal.  

3. Immerse it in a boiling antifreeze and water mixture.  

4. For additional information, refer to SPECIFICATIONS for water thermostat opening temperature.  

RADIATOR LEAK TEST, REMOVED FROM 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 

 

2003 Ford Pickup F150 

2003 ENGINE Engine Cooling - F150 Pickup

  

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

FAN CLUTCH TEST 

Spin the fan blade (8600) by hand. A light resistance should be felt. If there is no resistance or very high 
resistance, the minimum and maximum fan speeds must be checked as follows: 

Minimum Speed Fan Clutch Requirement Test 

1. Use a suitable marker to mark the water pump pulley (8509), one of the fan blade bolts, and the 

crankshaft pulley (6312).  

2. Connect a tachometer to the engine.  

3. Install a throttle adjusting tool.  

4. Connect a digital photoelectric tachometer. 

5. Start the engine and run it at approximately 1,500 RPM until the normal operating temperature has been 

achieved.  

6. Adjust the engine speed to 2,300 RPM.  

7. Adjust the strobe light to 3,000 RPM and aim it at the water pump pulley. Adjust the engine speed until 

the light flash and the water pump pulley mark are synchronized.  

8. Aim the strobe light at the fan blade retaining bolts. Adjust the strobe light until the light flash is 

synchronized with the marked fan blade retaining bolt (fan blade appears to stand still).  

9. The fan blade speed must not be greater than 1,500 RPM at 3,000 water pump RPM.  

10. Turn the engine off.  

11. If the fan blade speed was greater than 1,500 RPM, install a new fan clutch (8A616).  

Maximum Speed Fan Clutch Requirement Test 

1. Carry out Steps 1 through 5 of the MINIMUM SPEED FAN CLUTCH REQUIREMENT TEST. 

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 the tank.

WARNING:

To avoid the possibility of personal injury or damage to the vehicle, 
do not operate the engine until the fan blade has been first examined 
for possible cracks and separation. Failure to follow these 
instructions may result in personal injury.

NOTE:

The engine temperature should be above 96°C (205°F) for maximum fan 

 

2003 Ford Pickup F150 

2003 ENGINE Engine Cooling - F150 Pickup