Caution: To avoid being burned, do not remove the radiator cap or surge tank cap while the engine is hot. The cooling system will release scalding fluid and steam under pressure if radiator cap or surge tank cap is removed while the engine and radiator are still hot.

Caution: As long as there is pressure in the cooling system, the temperature can be considerably higher than the boiling temperature of the solution in the radiator without causing the solution to boil. Removal of the pressure cap while the engine is hot and pressure is high will cause the solution to boil instantaneously -- possibly with explosive force -- spewing the solution over the engine, fenders and the person removing the cap.

Does the engine appear to be overheating, with or without loss of coolant?

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Go to Engine Overheating

Go to Step 2

Is a loss of coolant evident?

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Go to Loss of Coolant

Go to Step 3

Does the engine fail to reach the normal operating temperature?

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Go to Engine Fails To Reach Normal Operating Temperature

Go to Step 4

1. With the engine cold, remove the radiator filler cap.
2. Remove a small amount of coolant from the radiator in order to prevent overflow as the engine warms up.
3. Run the engine until the thermostat opens.
4. Verify that the coolant is circulating in the radiator.

Is the coolant circulating?

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Go to Step 6

Go to Step 5

Feel around the radiator core.

Cold spots indicate that sections of the radiator core are clogged.

Are cold spots present?

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Go to Step 7

Go to Step 6

Remove the coolant outlet. Refer to Engine Coolant Thermostat Replacement .

Is the thermostat stuck closed or is the coolant outlet blocked?

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Go to Step 7

Go to Step 9

1. Inspect the coolant passage.
2. Probe the blockage with a piece of wire and flush until clear.
3. Reinstall the component.

Is the system OK now?

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System OK

Go to Step 8

Install new parts as necessary.

Is the system OK now?

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System OK

Go to Step 4

Inspect the crossover passage at the front of the inlet manifold (the thermostat must be removed for access).

Is this area clear?

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Go to Step 10

Go to Step 7

1. Ensure that the engine is at normal operating temperature.
2. Squeeze the (upper) radiator inlet hose while accelerating the engine speed.

Did you feel a pressure surge?

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Go to Step 14

Go to Step 11

Inspect for a plugged vent hole in the water pump.

Is the vent hole plugged?

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Go to Step 12

Go to Step 13

Remove the obstruction from the vent hole.

Does the cooling system operate properly?

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System OK

Go to Step 13

1. Remove the water pump.
2. Remove the rear cover.

Is a blockage present?

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Go to Step 7

Go to Step 14

1. Remove the cylinder head(s).
2. Inspect for discoloration or other signs of a blockage.

Does the cylinder head(s) require further inspection?

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Go to Step 7

Go to Step 15

Use a penlight in order to inspect the engine block for a clogged coolant passage.

Did you find a blockage?

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Go to Step 7

Go to Engine Exhaust Leaking into Coolant or Cooling System Noise