How to Test for a Head Gasket Leak

by Dianne Christensen-Herman
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External coolant leaks from your car can be easy to determine because the green or brownish liquid -- depending on the type of coolant -- is visibly leaking from hoses or other engine components onto the ground. However, coolant leaking internally can be more difficult to diagnose and usually means a blown head gasket. If your car is overheating and the coolant levels are decreasing, there is a radiator cap test, or what is sometimes referred to as a champagne test, you can administer. This test can determine if coolant is leaking in the head gasket and if it is blown. This will take just a few minutes of your time and no tools.

Step 1

Turn off the car and let it cool overnight. Open the hood.

Step 2

Locate the cap toward the front of the engine bay with a warning message imprinted on it, "Do not open when hot." This is the radiator cap. Twist it counterclockwise to open it, and set the cap in a safe place.

Step 3

Climb in the driver's seat and start the car once the cap is off. If the car has head gasket leaks or a blown gasket, you will see bubbles forming in the coolant when you look into the radiator filler neck. If your vehicle tests positive for a head gasket leak with this test, you should take it to be inspected by a licensed mechanic.

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