Pressure test
1. Turn off the engine.
2. Open the hood and install protective covers on the fenders.
WARNING: Do not, under any circumstances, remove the coolant expansion tank while the engine is running. Failure to follow these instructions may result in damage to the engine cooling system and personal injury. To avoid scalding with hot water or steam emitted from the cooling system, take extra care when removing the expansion tank from a hot cooling system. Wait until the engine has cooled down, then cover the expansion tank cap with a piece of thick cloth and turn it slowly until the pressure starts to release. When depressurizing the cooling system, move away from the expansion tank. When you are sure that the pressure is completely relieved, turn and remove the expansion tank cap without removing the thick cloth from it. Failure to follow these instructions may result in injury.
3. Carefully remove the expansion tank cap to relieve pressure in the cooling system. If necessary, add the correct coolant to the expansion tank of the cooling system.
4. Install the connector of the pressure tester (ensuring the tightness of the connections) between the overflow / air purge nipple and the overflow / purge hose in the expansion tank of the cooling system. Reinstall the expansion tank cap.
5. Connect the pressure pump and pressure gauge to the connector and pressurize the cooling system to a value that does not exceed the lower limit for the expansion tank cap.
6. Observe the pressure gauge for approximately two minutes. During this period, the pressure should not drop.
- If the system holds pressure, go to step 8.
- If pressure drops, check for leaks in hoses from engine to heater core, engine to radiator, bypass hose, water valve hose (in the presence of), thermostat housing gasket, radiator core, heater core, etc. If you cannot find a leak in the cooling system, also refer to checks on the engine system. Repair any leaks found and recheck the system.
7. Depressurize the system by releasing the expansion tank cap. Check coolant level. If necessary, add coolant of the correct concentration. For more information, see the information in this section.
8. Perform a pressure test on the cap of the expansion tank of the cooling system, proceeding in accordance with this section.
Pressure test of the cap of the expansion tank of the cooling system
WARNING: Do not, under any circumstances, remove the coolant expansion tank while the engine is running. Failure to follow these instructions may result in damage to the engine cooling system and personal injury. To avoid scalding with hot water or steam emitted from the cooling system, take extra care when removing the expansion tank from a hot cooling system. Wait until the engine has cooled down, then cover the expansion tank cap with a piece of thick cloth and turn it slowly until the pressure starts to release. When depressurizing the cooling system, move away from the expansion tank. When you are sure that the pressure is completely relieved, turn and remove the expansion tank cap without removing the thick cloth from it. Failure to follow these instructions may result in injury.
1. Carefully remove the expansion tank cap to relieve pressure in the cooling system. Add coolant to reservoir if necessary.
2. Clean the rubber seal and vacuum relief valve area with water. Immerse the bottle cap in water and install the bottle cap pressure test adapter (supplied with pressure tester) on the cover of the expansion tank.
NOTE: If the pump plunger is pushed too fast, the pressure reading will be incorrect.
3. Slowly depress the pressure test pump plunger until the pressure gauge stops rising.
4. Record the highest pressure value. Relieve pressure. To do this, turn the pressure relief screw counterclockwise. Then tighten the pressure relief screw and repeat step 5 at least twice to check the stability of the pressure gauge reading and make sure that the reading is within the limits for the expansion tank cap.
5. If the reading on the pressure gauge is out of range for the expansion tank cap, install a new expansion tank cap.
Thermostat check
A new thermostat should only be installed after the following checks have been made.
Electrical thermostat test
WARNING: Always vent exhaust gases outside when performing this check. Failure to follow this instruction may result in injury.
NOTE: The procedure gives the most accurate results when performed indoors at an ambient temperature below 37.8°C (100°F). This test can be performed with the hood open or closed, with the engine warm or cold.
1. Check the coolant level in the radiator and expansion tank of the cooling system. Top up coolant if necessary.
2. With the engine off, disconnect the plug connector of the cylinder head temperature sensor (SNT) and connect the coolant temperature control harness using it as a jumper between the PCM and the CHT sensor. Connect a digital multimeter to the thermostat wiring harness. Now the voltage values (0 V to 5 V) can be checked without disturbing the connection of the sensor to the electrical wiring.
NOTE: Performing this test with the gear engaged or engaged (working) air conditioning compressor clutch will cause a misdiagnosis.
3. Move the gearbox to position «R» («parking») or «N» («neutral position»).
4. Start the engine and let it idle throughout this check. Let the engine run for 2 minutes, then record the CHT sensor voltage. Record the SNT sensor voltage every 60 seconds. When the general voltage trend of the SNT sensor changes direction or the voltage changes only slightly (0.03 V or less) compared to the previous value, register this value as the thermostat opening voltage. Use the Voltage to Coolant Temperature Chart below.
| Coolant temperature°C (°F) | SNT (IN) |
| 20 (68) | 3,09 |
| 40 (104) | 2,15 |
| 70 (158) | 1,04 |
| 80 (176) | 0,79 |
| 90 (194) | 0,61 |
| 95 (203) | 0,53 |
| 105 (221) | 0,41 |
5. If the thermostat opening voltage exceeds 0.79V and corresponds to a temperature less than 80°C (176°F), install a new thermostat.
6. If the thermostat opening voltage is less than 0.79V and corresponds to a temperature greater than 80°C (176°F), The thermostat is in good condition and does not need to be replaced. Refer to the Symptom Table for further instructions.
Mechanical thermostat check
NOTE: Fully open means the thermostat valve is 5.8mm or more above the seat.
Remove the thermostat and submerge it in a boiling mixture of antifreeze and water. The thermostat should start to open when:
- 82°C (179°F) - vehicles with 1.6L Zetec-SE/1.4L engine.
- 82°C (179°F) - vehicles with 1.6L Duratec engine.
- 92°C (197°F) - vehicles with 1.8L/2.0L/1.6L Zetec-E engine.
- 87°C (188°F) - vehicles with 1.8L Diesel engine.
The thermostat must be fully open when:
- 96°C (204°F) - vehicles with 1.6L Zetec-SE/1.4L engine.
- 96°C (204°F) - vehicles with 1.6L Duratec engine.
- 99°C (210°F) - vehicles with 1.8L/2.0L/1.6L Zetec-E engine.
- 102°C (215°F) - vehicles with 1.8L Diesel engine.
Install a new thermostat if it does not work as directed:
- Vehicles with 1.6L Zetec-SE/1.4L engine. For more information refer to Thermostat available in this section.
- Vehicles with 1.6L Duratec engine. For more information refer to Thermostat-1.6L Duratec available in this section.
- Vehicles with 1.8L/2.0L/1.6L Zetec-E engine. For more information refer to Thermostat available in this section.
- Vehicles with 1.8L Diesel engine For more information refer to Thermostat available in this section.
- Vehicles with 2.0L Duratec ST engine For more information, refer to Thermostat available in this section.
If the thermostat does not work as prescribed, install a new thermostat. If there is no heat source available for this test, check the thermostat for leaks. Hold the thermostat against a background light source. Light entering through the new thermostat valve at room temperature indicates that a new thermostat should be installed. Some thermostats have a small amount of light in one area around the perimeter of the thermostat valve, which is considered normal.
Check for leaks in the radiator removed from the car
CAUTION: Do not leak test an aluminum heatsink in the same water that is used to test for leaks on copper/brass heatsinks. Flux and alkaline cleaners may be present in the test water and will corrode the aluminum.
Before starting the test, clean the radiator to prevent contamination of the test tank. Checking the radiator for leaks should be carried out in clean water at an air pressure of 138 kPa.
For aluminum radiators, it is recommended to use a separate clean test tank. If a separate tank for testing aluminum radiators is not available, the test tank should be flushed each time before testing an aluminum radiator.
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