1. Pressure test the cooling system and the cap for leaks. Refer to Cooling System Leak Testing
2. Repair any leaks before proceeding These engines use a 82°C (180°F) thermostat. The ambient temperatures should be within the specified range given.
3. Set the HVAC controls in the off position.
4. Run the cold engine at idle (68-70°F) for 15-20 minutes before reading the engine temperature.
5. Read the engine coolant temperature at idle with the Scan Tool .

Is the engine coolant temperature between 85-96°C (185-205°F)?

13-38°C (55-100°F)

System OK

Go to Step 2

Is the engine coolant temperature below 85°C (185°F)?

--

Go to Step 3

Go to Step 4

The thermostat is opening early, or the thermostat seal is leaking.

Replace the thermostat and the thermostat seal. Refer to Engine Coolant Thermostat Replacement .

Is the repair complete?

--

System OK

--

Is the engine coolant temperature over 96°C (205°F)?

--

Go to Step 5

--

Is the radiator inlet hot?

--

Go to Step 6

Go to Step 7

1. Turn on the heater.
2. Determine whether hot air is coming from the heater outlets.

Is the air hot?

--

Go to Step 11

Go to Step 12

Air may be in the system.

1. Add coolant to the surge tank if the coolant level is low.
2. Reexamine the radiator inlet hose.

Is the inlet hose hot?

--

Go to Step 6

Go to Step 8

Inspect for blockage in the following areas:

Did you find a blockage?

--

Go to Step 9

Go to Step 10

1. Repair the blockage.
2. Read the coolant temperature with the Scan Tool .

Is the repair complete?

--

System OK

--

1. Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .
2. Read the coolant temperature with the tech 1 .

Is the repair complete?

--

System OK

--

Inspect for blockage in the radiator.

Did you find any blockage?

--

Go to Step 9

Go to Step 10

1. Accelerate the engine several times in order to remove any air from the system.
2. Inspect for blockage in the heater circuit. Refer to Function Test in Heating, Ventilation, and Air Conditioning.
3. Inspect for any pinched or buckled hoses.

Did you find any blockage?

--

Go to Step 9

Go to Step 13

Refer to Heater Diagnosis in Heating And Ventilation System.

Is the repair complete?

System OK

--