How to Test a Radiator for Blockage

by Gail Delaney
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radiator humor image by John Sfondilias from

If you use your car and suspect that the radiator has a blockage, then continuing to drive can compromise your car's cooling system and eventually lead to serious engine damage. If your car overheats when driving at normal speeds or upon heavy acceleration, you may have a blockage in your radiator. You can take it to the repair shop and have a mechanic check the radiator, but you can test the radiator yourself to see if there is a blockage.

Warm Engine Test

Step 1

Run the car. Go for a drive to bring the car's engine to normal temperature.

Step 2

Turn off the car and open the hood.

Step 3

Feel all around the outside of the fins of the radiator core with your hands, but not the top of the radiator, because you can get burned.

Determine if you have any cold spots. If you feel any cold places, that indicates you have a blockage in the radiator.

Cold EngineTest

Step 1

Remove the radiator cap when the engine is cold.

Step 2

Start the engine and allow it to run for three to five minutes.

Step 3

Shine a flashlight in the radiator and see if any fluid is flowing. If the fluid is not moving, or if the fluid resembles brown soup, this is an indication that your radiator is blocked.

Turn the car off and listen. If your radiator sounds like it is boiling, this also indicates a blockage.

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