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Car Care Advice

How to Detect a Head Gasket Leak: 9 Critical Signs

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A head gasket leak can be catastrophic for your engine if ignored. Luckily, there are often signs that appear before the damage becomes irreparable.

So, how do you spot a head gasket leak in your car?
And what’s causing this issue in the first place?

No need to worry. 
We’re here to help you detect a leaky head gasket and share tips to prevent this headache.

Let’s begin.

This Article Contains: 

What Does a Head Gasket Leak Mean?

The head gasket is a vital seal between the engine block and cylinder head. It keeps combustion chambers, coolant passages, and oil channels separated and sealed. 

When the head gasket fails, coolant or antifreeze drips into the cylinder areas and oil passages, compromising the engine’s function. If left untreated, this can lead to costly engine repair costs.

The most effective way to prevent such a catastrophic situation is by identifying the warning signs early. 

Let’s explore these symptoms. 

9 Common Signs of a Head Gasket Leak

If you’re concerned about a blown head gasket, keep an eye out for these signals:

1. Lit Check Engine Light 

An illuminated check engine light is an early warning sign that something is wrong with your vehicle. However, to identify the issue accurately, you’ll need an OBD scan tool to read the trouble code stored by the Engine Control Unit (ECU). If you see error code P0300, it points to a head gasket failure.

2. Discolored Engine Oil or Coolant Contamination

Milky colors or ‘cloudiness’ in your motor oil indicate that coolant has entered the oil passages. To check this, use the dipstick to inspect the motor oil residue for any milkshake-like appearance or unusual coloration.

Similarly, if oil floats on top of the coolant, it suggests an oil leak into the coolant passage, often caused by a head gasket failure.

3. Loss of Power 

In severe cases, a blown head gasket or gasket failure can reduce engine power. This happens because leaked coolant can block the smaller openings in the engine, hindering oil flow and affecting combustion needed for proper engine function. 

4. White Smoke 

Head gasket leaks or a blown head gasket can cause white smoke from the tailpipe or exhaust, which indicates that water or coolant runoff has reached the cylinders and burned. This can also cause a sweet or classic ‘head gasket scent’ because the coolant mixes with the oil.

Common signs include wet spots, puddles, or dried coolant residue around the engine, particularly near the cylinder head and engine block.

5. Engine Overheating 

A head gasket leak may allow oil or combustion gasses to enter the coolant passages. These contaminants can create deposits or sludge that block coolant flow through important channels. As a result, the coolant’s ability to dissipate heat effectively is compromised, leading to a rapid increase in engine temperature.

6. Low Coolant Levels

Coolant can leak out of the engine when the head gasket seal is ruptured, leading to low coolant levels and a sudden hike in your engine’s temperature. You can identify external leaks by inspecting the ground beneath your vehicle for puddles or stains, especially near the front of the engine or radiator. 

If you notice a gradual decrease in coolant levels without any visible external leaks, it could indicate an internal leak. 

7. Knocking Noises from the Engine 

Hearing a knocking noise from the engine can be a sign of engine failure, as this can occur when the engine isn’t properly lubricated. A head gasket leak or blown gasket may allow oil into the combustion chamber, causing incomplete combustion or carbon deposits on the piston or cylinder walls. These deposits create hot spots within the combustion chamber, leading to premature ignition of the air-fuel mixture and causing knocking or pinging noises.

A bad head gasket or gasket failure can also reduce compression in one or more cylinders in more severe cases. Loss of compression leads to inefficient combustion and uneven engine operation, resulting in knocking or rattling noises as the engine struggles to maintain smooth operation. 

8. Bubbling Coolant 

When the engine coolant overheats, it boils and forms bubbles, visible in the radiator or reservoir (AKA overflow tank).

A faulty head gasket can also allow engine combustion gasses to enter the cooling system. These gasses can gather in the coolant, creating air pockets or bubbles.

9. Misfires 

Misfires are one of the most noticeable signs of a blown head gasket. Coolant mixed with the air-fuel mixture in the cylinder can lead to incomplete combustion or spark disruption, resulting in misfires. This can lead to a lit check engine light, sudden loss of engine power, and rough idling, all of which can indicate a misfire or other engine trouble.

With a clearer picture of what to watch out for, let’s uncover the underlying causes that can lead to this issue.

3 Major Causes of Head Gasket Leaks

Here are three common reasons behind a faulty head gasket:

1. Engine Overheating

When your car’s engine overheats, the metal parts inside expand excessively, potentially warping the head or cylinder block. Warping or damage can lead to coolant or oil leaking into the cylinders.

2. Wear and Tear Over Time

The cylinder head gasket wears out from exposure to high temperatures and pressure cycles over time. This can cause the gasket material to degrade, become brittle, or lose its ability to seal properly.

3. Poor Installation or Quality Issues

Sometimes, head gaskets fail because the head bolts aren’t installed correctly during engine assembly or maintenance. If the gasket isn’t placed or tightened properly or made from low-quality materials, it may not be strong enough to handle the heat and pressure inside the engine.

Next, let’s assess how a blown head gasket impacts your vehicle’s overall safety and reliability.

Is It Safe to Drive with a Leaking Head Gasket

It’s not safe to drive with a blown head gasket. If you continue to drive without servicing your vehicle, you risk total engine failure. 

If you’re driving and you encounter signs that could indicate a blown or cracked head gasket, be sure to pull over and call your local tow service or contact a mobile automotive repair shop like AutoNation Mobile Service. We’ll be able to advise whether you need a gasket sealer for head gasket repair or a head gasket replacement

Typically, stop-leak products like a head gasket sealer can provide a quick and cost-effective way to address minor leaks. 

But what if you have no option but to drive?
If there’s no option for a tow, watch for signs of an overheated engine or power loss in the engine, and drive as cautiously as possible to avoid engine strain.

Ultimately, properly diagnosing a blown gasket is crucial for effective repairs, vehicle safety, cost savings, and minimizing environmental pollution.

How to Diagnose a Bad Head Gasket

For an accurate diagnosis of a cylinder head gasket leak, it’s best to have your vehicle inspected by a skilled mechanic or automotive technician. Mechanics have the necessary tools and expertise to identify head gasket issues correctly. 

But if you still wish to know how it’s done, here’s a general know-how on the different diagnostic tests a mechanic will undertake:

A. Coolant System Pressure Test

During this test, a specialized tool is connected to the radiator or coolant reservoir, and the system is pressurized with air. Here’s how: 

  1. Attach the pressure tester to the coolant reservoir or radiator.
  1. Pump it to the pressure level specified in your vehicle’s service manual. 
  1. If there is a rapid pressure drop, it suggests a coolant leak.

B. Compression Test

This test helps evaluate the condition of an engine’s internal combustion chambers, particularly the piston rings, cylinder walls, and valves. For this, a mechanic will: 

  1. Disconnect the spark plug wires and remove the spark plug
  1. Then, attach a compression gauge to each cylinder one at a time and crank the engine several times to measure the compression in each cylinder. 
  1. Compare the compression readings between cylinders. 
  1. Significant variations in compression levels, especially between adjacent cylinders, can indicate a failed head gasket affecting compression.

C. Combustion Leak Test

This diagnostic procedure is used to detect leaks within the engine’s combustion chamber. The mechanic will: 

  1. Place the tester’s fluid over the coolant reservoir or radiator opening.
  1. Watch for any color changes in the fluid.
  1. If the fluid changes color (especially to yellow or blue), it indicates the presence of combustion gasses, typically due to a failed head gasket. 

While diagnosing and fixing issues like head gasket leaks is important, focusing on preventive measures to avoid these problems entirely is even more crucial. 

6 Effective Ways to Prevent a Head Gasket Leak

Here are some steps you can take to help prevent a head gasket leak:

  1. Follow your vehicle’s maintenance schedule for engine oil changes, coolant flushes, and inspections.
  1. Use the recommended engine coolant and maintain the correct coolant-to-water ratio.
  1. Keep an eye on the temperature gauge to prevent overheating.
  1. Fix cooling system problems promptly to avoid stress on the head gasket.
  1. Drive within the recommended RPM (Revolutions Per Minute) range to reduce stress on engine components.
  1. Use original manufacturer parts when replacing the head gasket. 

Fix Head Gasket Problems Effortlessly with AutoNation Mobile Services

A head gasket problem is a serious issue that can cause significant engine troubles. That’s why it’s crucial to recognize the signs early to prevent severe damage and expensive repairs. 

However, if you face head gasket issues that need immediate attention, remember that AutoNation Mobile Services is here to help.

We’re a mobile auto repair and maintenance company that offers upfront pricing and a 12-month, 12,000-mile repair warranty on all services.

Contact us for a blown head gasket repair or any other automotive problems like brake repair, radiator cap issues, etc.