A blown or failing head gasket can produce a few distinctive sounds that can alert drivers to the issue. In this article, we’ll discuss the common sounds produced by a bad head gasket and what causes them. We’ll also provide some background on what the head gasket does and why it can fail.
What is a Head Gasket?
The head gasket is a crucial component that seals the engine block to the cylinder head. Its main functions are:
- Creating a tight seal between the engine block and cylinder head to contain combustion pressures
- Sealing coolant and oil passageways
- Providing proper compression in the cylinders
The head gasket endures tremendous stresses from heat cycles, combustion pressures, vibration, and clamping force. Over time, these stresses can cause the head gasket to fail. Common reasons for head gasket failure include:
- Overheating – Repeated overheating episodes can warp or crack the head and block surface, preventing a tight seal.
- High mileage – The head gasket material degrades over time.
- Improper torque – Incorrect tightening or uneven clamping force can result in localized failure spots.
- Physical damage – External impacts can distort the head or block surface.
When the head gasket loses its ability to seal the cylinders, several symptoms can appear. The most common signs of a blown head gasket are:
- Overheating
- White exhaust smoke
- Coolant leaks
- Oil contamination
- Loss of power
- Unusual noises
In this article, we’ll focus specifically on the sounds produced by a bad head gasket and what causes them.
Hissing or Ticking Sound from the Engine
One of the most common sounds of a blown head gasket is a hissing or ticking noise coming from the engine. This sound occurs when combustion gases escape through the compromised gasket seal and enter the cooling system.
As cylinder pressure increases during the combustion stroke, some of this pressure can leak past the damaged gasket and push into the cooling passages. This creates air bubbles in the coolant, which collapse shortly after when cylinder pressure decreases. The rapid collapsing of air bubbles produces a ticking or hissing noise from the engine block.
The noise is often most noticeable at idle, when the engine is running but cylinder pressures are lower. The sound may disappear as engine RPMs increase. Drivers typically describe the noise as:
- Ticking or tapping
- Intermittent hissing
- Bubbly churning
This sound can come directly from the cylinder head area or radiator as combustion gases permeate the cooling system.
Bubbling Sound from the Radiator or Reservoir
In addition to cylinder head ticking, a blown head gasket can cause bubbling noises from the radiator or coolant reservoir as excess combustion gases accumulate in the system.
With a compromised head gasket, the entire cooling system can become pressurized by gases blowing by into the passages. These gases get trapped in the radiator and coolant reservoir and manifest as bubbling or percolating noises.
Drivers may notice the coolant reservoir boiling more vigorously than usual. The radiator cap may also release built up pressure in bursts.
If the head gasket damage is severe enough, the bubbling and release of pressurized gases can occur constantly at idle or while driving. This noise indicates a significant amount of combustion gas is entering the cooling system.
Knocking or Pingling from the Engine
Engine knocking or pinging can also be a sign of a blown head gasket. This noise occurs when abnormal combustion takes place in the cylinders.
Several things can happen when the head gasket fails between cylinders:
- Coolant can leak into the cylinders. Coolant does not compress like air, which causes erratic combustion.
- Compression can leak between cylinders, causing pre-ignition and detonation.
- The open gasket can cause the cylinders to overheat, increasing the chance of knock.
The result is premature ignition of the fuel-air mixture which causes a loud pinging or rattling noise from the engine. This abnormal combustion often worsens under acceleration.
Knocking sounds from a damaged head gasket may be most noticeable at specific engine operating points or loads. Some drivers describe the noise as:
- Metallic pinging, clicking or rattling
- Popping or snapping sounds
- Noise that changes with engine speed
Knocking noises point to erratic combustion and high stresses caused by the blown gasket, which can quickly lead to engine damage if left unchecked.
Loss of Power and Performance
In addition to unusual sounds, a noticeable loss of engine power is common with a blown head gasket. Several factors contribute to reduced performance:
- Compression loss – Leaking seal causes low cylinder compression
- Overheating – High temperatures lead to lower output
- Misfires – Coolant leaks and detonation disrupt combustion
- Knock sensor retardation – The knock sensor detects detonation and retards ignition timing
Drivers may experience a lack of power during acceleration, decreased engine RPMs, and an inability to achieve high speeds. The engine may feel sluggish overall.
If coolant leaks into the engine cylinders, white smoke may also come from the exhaust as the coolant burns. This condition is most noticeable on acceleration as cylinder pressures increase.
Identifying the Location of the Noise
Determining if the unusual sounds are coming from the cylinder head area or elsewhere in the engine can help diagnose a blown head gasket.
Here are some tips for locating the source of the noise:
- Open the hood with the engine idling to listen for the location of knocking or hissing sounds.
- Carefully use a mechanic’s stethoscope or long screwdriver to isolate the noise by placing the tip on different engine components.
- Feel for vibration or movement on the suspected area.
- Remove engine covers and accessories if needed to get closer to the source.
- Have an assistant rev the engine during diagnosis to change the noise.
Focusing your inspection on the cylinder head, valvetrain, and timing components can help determine if the noise is related to the head gasket failure.
Other Head Gasket Failure Symptoms
In addition to strange sounds, here are some other symptoms of a blown head gasket to look for:
- Overheating – Coolant leaks cause rapid overheating and fluid loss.
- Milky oil – White deposits in the oil indicate coolant mixing.
- Visible leaks – External leaks around the head gasket surface.
- White exhaust – Burning coolant produces white exhaust smoke.
- Check engine light – Sensor faults trigger error codes due to overheating or misfires.
Noticing several of these warning signs in conjunction with unusual noises points strongly to head gasket failure.
Preventing Blown Head Gaskets
Here are some tips to help prevent premature head gasket failure:
- Maintain proper coolant levels and change it per the maintenance schedule.
- Keep an eye on engine operating temperatures and don’t let it overheat.
- Replace the head gasket and get the head checked for warpage if it has overheated.
- Use only approved coolants and don’t mix incompatible types.
- Check for external leaks and get them fixed promptly.
- Don’t rev the engine excessively or overload it.
- Install quality parts and don’t reuse old head bolts.
- Keep oil levels stable and change it regularly.
When to Repair a Blown Head Gasket
Driving with a blown head gasket can quickly lead to additional engine damage. Overheating, coolant loss, and contamination will degrade internal components.
Unusual noises from a damaged head gasket indicate combustion gases or coolant are leaking into areas they shouldn’t be. Even if the vehicle seems to be running normally, the underlying problems will persist and worsen.
Head gaskets should be replaced as soon as possible once you confirm the failure. Continued driving risks further damage to the head, block, pistons, bearings, and other critical engine components.
Head Gasket Replacement Cost
The average cost for a head gasket replacement at a repair shop is typically between $1,000-$2,000. Here are some of the factors that affect the overall repair cost:
- Labor time – More complex engine designs take longer.
- Parts cost – Premium gaskets and hardware is more expensive.
- Machine work – Resurfacing the head or block if damaged adds to cost.
- Location – Prices are higher in some geographic areas.
- Engine size – Bigger motors cost more to service.
- Garage hourly rate – Varies between repair shops.
Getting quotes from a few different mechanics can help find the best value. Also ask what is included with the head gasket service, as some shops provide a limited warranty on parts and labor.
Conclusion
Unusual ticking, knocking, bubbling, and hissing sounds when paired with other symptoms can indicate a blown head gasket. This failure allows combustion gases to enter the cooling system or liquid coolant to leak into engine cylinders and mix with oil.
Left unchecked, the compromised seal leads to further overheating, contamination issues, performance loss, and internal component damage. Have your vehicle inspected as soon as possible if these sounds arise to prevent exacerbating the problem. Getting the head gasket replaced quickly reduces the chances of requiring more extensive engine repairs down the road.