What Are the Symptoms of a Blown Head Gasket?

A hot gauge changes the plan

When several clues appear together, we'd give a rising temperature gauge priority, because overheating can signal gasket trouble and can also damage the seal. Once the engine is off, the other observations will help you describe what happened.

White exhaust and disappearing coolant

The head gasket separates the cylinders from coolant and oil passages. If coolant gets past that seal into a cylinder, white smoke may come from the tailpipe at startup or while driving, and coolant may disappear without an obvious leak. White smoke isn't present in every case.

Bubbles you already noticed in the radiator or coolant reservoir are another clue. A leak from a combustion chamber into the cooling system can raise pressure there, leading to a failed hose or leaks at a water pump, radiator neck or cap. Note where you saw the bubbles and whether coolant loss appeared with them.

Changes in oil and exhaust

Look for a milky-white change in the oil's color or texture. A milky-white film you already noticed beneath the oil filler cap is worth reporting too: a leak between coolant and oil passages can let the fluids mix. Describe the appearance you saw without taking anything apart to investigate it.

Blue-gray tailpipe smoke paired with increased oil consumption suggests a different possible path through the gasket, from an oil passage into a combustion chamber. Note whether the exhaust looked white or blue-gray and whether oil consumption changed. Those details help distinguish the observations you made.

Changes in how it runs

If starting has become difficult, note whether it happened after you first noticed the other symptoms. A failing seal can let cylinder compression fall, making the engine hard to start. As coolant enters a combustion chamber, misfires and faster coolant consumption can follow.

Lost power can fit a leak between neighboring cylinders because compression falls there too. If the change followed overheating, record whether a malfunction indicator light appeared with reduced performance. Tell the technician which change you noticed first, along with any white exhaust or coolant loss you saw at the time.

What overheating can mean

Overheating can be a sign of gasket trouble and can also cause it. Low coolant, a failed water pump, radiator fan or coolant hose, or extreme temperatures can raise engine heat enough to warp the surfaces the gasket seals. That gives the temperature reading a useful place in your account of when the symptoms began.

Think back to whether the temperature kept rising, a malfunction indicator light came on with reduced performance, or white smoke appeared from the engine compartment. A sweet smell from the engine compartment or exhaust may also have accompanied the overheat. Record what you noticed before shutting the engine down.

The parked leak check

With the engine off, look for oil or coolant streaks down the outside of the head gasket and for visible fluid near hoses, seals or a water pump. A leak at one of those places is useful to locate, but a cracked head can produce symptoms similar to a damaged gasket. The observations tell the technician where to investigate, rather than naming the failed part.

Put a large piece of paper beneath the parked vehicle overnight to see where fluid falls. In the morning, note the position and color of any spot. Green, orange, blue, pink or yellow fluid could be coolant from a radiator, hose, water pump, gasket or seal.

Coolant can also land on a hot engine and burn off without leaving a spot on the ground, sometimes leaving a white deposit. If coolant has been disappearing with no obvious leak, a technician may pressure-test the cooling system for an external leak or use dye to trace one. Write down the paper check's result alongside the oil appearance, exhaust color, warning lights and when each symptom appeared.