Blown Head Gasket: Signs, Causes, and What to Do Next

When your engine starts acting up—overheating, losing coolant, or blowing white smoke from the exhaust—you might be dealing with a blown head gasket, a sealed joint between the engine block and cylinder head that keeps coolant, oil, and combustion gases separate. Also known as a head gasket failure, this isn’t just a minor leak—it’s a critical breakdown that can destroy your engine in days if ignored. The head gasket takes extreme heat and pressure, and when it fails, everything gets mixed up: coolant enters the cylinders, oil mixes with coolant, and combustion gases escape where they shouldn’t.

This kind of failure doesn’t happen out of nowhere. It’s usually caused by engine overheating, when the engine runs too hot for too long, warping the cylinder head and crushing the gasket. Maybe you drove with low coolant, ignored a warning light, or had a faulty thermostat. It can also come from a poorly tuned engine, detonation (knocking), or even a manufacturing defect. Once the seal breaks, you’ll start seeing coolant leak, a telltale sign where coolant drips from the engine or pools under the car, often near the cylinder head. You might also notice milky oil—like chocolate milk—because coolant is mixing with your engine oil. Or worse, bubbles in the radiator when the engine runs, meaning exhaust gases are leaking into the cooling system.

Some people try to fix this with sealant additives. Don’t. Those products rarely work on a true blown head gasket—they might slow a tiny leak, but they won’t fix the underlying damage. You need a proper diagnosis: a compression test, a block test for exhaust gases in coolant, or checking for hydrocarbons in the radiator. If the head gasket is gone, the cylinder head may be warped. If it’s warped, it has to be resurfaced or replaced. And if the engine ran hot for too long, the pistons or valves could be damaged too. Replacing a head gasket isn’t cheap, but it’s cheaper than a new engine.

Below, you’ll find real-world guides that show you how to spot these symptoms before it’s too late, how to test for a blown head gasket without a shop, and what parts you might need if you’re planning a repair. Some posts cover related issues like low oil, fuel pump failures, or radiator problems—all of which can lead to overheating and eventually, a blown head gasket. This isn’t just about fixing a part. It’s about understanding how your engine works, why things break, and how to avoid the big repair bills that come from waiting too long.