Diagnosing a Blown Head Gasket: Symptoms and Testing

A blown head gasket can be a serious issue for your vehicle's engine, especially if left unaddressed. Here, we will look at common signs that your head gasket might be failing, as well as effective testing methods to diagnose the problem.

What Is a Head Gasket?

A head gasket is a critical component in your engine, sandwiched between the cylinder head and the engine block. Its primary function is to seal the combustion chambers and prevent coolant and oil from leaking into each other, among other sealing duties.

Signs of a Blown Head Gasket

Several symptoms can indicate that your head gasket is blown. Here are some of the most common signs:

Engine Overheating: A worn or blown head gasket can allow coolant to escape, causing the engine to overheat and showing up on the coolant temperature gauge as abnormally high. Low Coolant Levels: If your coolant level is constantly low and you keep topping it up, this could be a sign of a blown head gasket. Contaminated Engine Oil: If your engine oil contains coolant or looks frothy, milky, and brown, it's a strong indication of a blown head gasket. This contamination can be verified by draining and inspecting the oil. Advanced Compression Testing: A direct compression check will show a low reading on the affected cylinder, confirming a blown head gasket. Compression Differential Testing: By using a differential compression tester, you can pinpoint the exact cylinder that is affected. Bubbles in the coolant are another clear sign of a head gasket failure during this test. Pressure Test: Performing a cooling system pressure test can show whether the head gasket is leaking into the water jacket.

Coolant in Oil Signs and Testing

One way to detect a blown head gasket is to check the engine oil. If the oil is contaminated with coolant, it turns a milky, frothy, and brown color. In the past, Air Care technicians used gas analyzers to check for hydrocarbons in the coolant, which indicated a blown head gasket.

To perform a more accurate test, NAPA offers a Universal Combustion Leak Test Kit (Part Number BK 700–1006). This kit is designed to detect any combustion gas in the cooling system. Simply attach the tester to the radiator opening while the engine is running. If there is a combustion gas leak, the fluid in the tester will change color, signaling a head gasket problem or other combustion-related issues.

Conclusion

A blown head gasket can have serious consequences if not addressed promptly. Early detection via the signs and testing methods discussed here can save you from more extensive and costly repairs down the line. Remember, prevention and timely diagnosis are key to maintaining a healthy engine.

If you suspect a blown head gasket, it's best to consult a professional mechanic or use one of the diagnostic kits mentioned to confirm the issue before proceeding with any repairs.