Can A Bad Thermostat Cause A Blown Head Gasket?

can a bad thermostat cause a blown head gasket

Is there any connection between a bad thermostat and a blown head gasket? Can the thermostat’s defect destroy the gasket, or is that an unproven myth? The guide below has the answers.

Can A Bad Thermostat Cause A Blown Head Gasket?

Yes, a bad thermostat causes a blown head gasket. A thermostat can cause overheating by getting stuck in the closed position, which prevents the coolant from flowing. Once the coolant refuses to flow, the heat will increase, destroying the gasket.

Head gaskets are incredibly important despite their friendly price tags. This is what you should know about them:

  • According to this paper in the International Journal of Scientific And Engineering Research (Varunraj Varatharaj, Vishnu K R, Pavan B, Darshan K N), the head gasket sits between the cylinder head and engine blocks, from where it prevents leakages.
  • The engine relies on several vital fluids, including combustion gases from the air/fuel mixture, coolant in the hoses, and motor oil that provides lubrication. These substances typically operate within separate circuits. The gasket forms a seal that prevents them from mixing.
  • Without the gasket, coolant would flow into the oil and oil into the cylinder, disrupting the engine’s work and creating instances of overheating.
  • Manufacturers make head gaskets using robust materials that withstand extreme elements. For instance, polytetrafluoroethylene provides chemical resistance and reduces energy wastage due to its low coefficient of friction. Pyrophyllite offers impressive thermal stability and decent pressure flow attributes. Carbon fiber has a high tensile strength.

Despite these properties, head gaskets are not indestructible. They are particularly vulnerable to high temperatures. Optimal engine temperatures typically range between 190 and 220 degrees F. However, the experts at Global Cars Brands have found that temperatures under the hood can rise as high as 400 degrees F.

A paper from the Department of Mechanical Engineering at the National Cheng-Kung University in Taiwan (investigating the effects of gasket opening on engine temperature distribution) noted that a cooling system is expected to remove 33 percent of an engine’s combustion energy.

That is a significant amount of heat. Without the cooling system, you will lose the head gasket. Without a healthy head gasket, your vehicle will break down. As the guide below will soon reveal, high temperatures and bad thermostats go hand in hand.

Overheating And Gasket Stress

Most gaskets fail because of excess heat. As such, you have every reason to blame gasket stress on high temperatures, especially if the gasket blows.

How A Faulty Thermostat Can Lead To Engine Overheating?

If excess heat destroys head gaskets, how does a thermostat contribute to the high temperatures in an engine?

The thermostat regulates engine temperature by determining when the coolant flows. The thermostat has a valve that stays closed so long as temperatures are below a pre-determined threshold.

The engine requires a certain amount of heat to do its work. But too much heat can destroy the engine. The thermostat is designed to open and release the coolant when temperatures are too high. The coolant will pick up heat as it circulates through the engine block.

What happens when the coolant absorbs too much heat? The coolant will transition through the radiator, where it will cool before returning to the engine block. Naturally, a thermostat that doesn’t work is a threat because it can restrict the coolant flow, allowing the heat to accumulate.

Link Between Excess Heat And Potential Head Gasket Stress

Head gaskets are designed to tolerate an engine’s normal operating temperature. But if the cooling system stops working, the heat will exceed the gasket’s capacity. It will expand and warp.

This assumes that excess heat is the only factor at play. Fel-Pro has warned of situations where detonation breaks the rings and armor. The material will warp, allowing substances that typically stay separate to mix.

Pre-ignition is another occurrence that exposes the gasket to more heat and pressure than it can tolerate. But the head gasket is the least of your worries. The pistons and valves are more expensive to replace, and yet, they can also fail because of pre-ignition and detonation.

Stuck-Closed Thermostat Effects:

What makes the closed thermostat more dangerous than its open counterpart? Can it contribute to the gasket’s failure?

Consequences Of A Thermostat Stuck In Closed Position

New Kids Car has diagrams of a thermostat in the closed and open position. An essential aspect of the thermostat is the valve, which opens and closes in response to the engine temperature.

An open thermostat allows the coolant to flow. This is good if the engine is too hot. It only poses a threat when the engine temperature is still within the optimal range. A thermostat that sticks in the open position will force the engine to run colder than necessary. A thermostat stuck closed will produce the opposite results, attracting the following consequences:

  • The engine will overheat.
  • Hoses will rapture.
  • Radiators will sustain damage.
  • Coolant levels will fall.
  • The engine will lose power.
  • The temperature gauge will go into the red.

You can tell that a thermostat is stuck in the closed position because the valve will refuse to open when you place the component in a pot of hot water.

How Restricted Coolant Flow Can Cause Overheating And Gasket Concerns?

If the gasket sticks in the open position, the engine will take longer than you would like to warm up because the coolant flows continuously. It keeps taking the heat away. A closed thermostat stops the coolant flow.

Temperatures under the hood will skyrocket because there’s no coolant to draw the heat away. This is why a thermostat stuck closed threatens the gasket. By restricting the coolant flow, a closed thermostat will expose the gasket to dangerously high temperatures.

Pressure Buildup And Gasket Weakness:

Like the temperature, gaskets are expected to withstand significant pressure. Can high temperatures from a bad thermostat influence the pressure?

How Overheating Leads To Increased Cooling System Pressure?

  • Cars have a radiator cap set to 15psi. The component includes a pressure release valve.
  • When you expose a trapped liquid to heat, the pressure climbs as the liquid in question expands.
  • The cap waits for the pressure to reach 15 psi before opening the valve and allowing the coolant to escape. This protects the cooling system from the destructive effects of the skyrocketing pressure.
  • The pressure valve reverses its function when temperatures fall, and the pressure reduces. A vacuum opens a spring-loaded valve and draws coolant from the expansion tank to replace what was lost.

As you can see, heat is your biggest threat where the pressure is concerned. Have you noticed that experts discourage you from removing the radiator cap when the engine is hot? The coolant will explode from the radiator’s opening to burn you because of the considerable pressure in the cooling system.

A thermostat stuck in the closed position will add to that pressure by allowing the engine’s temperature to climb dramatically. However, the cooling system pressure can also rise because of a bad radiator cap.

Influence Of Pressure On Head Gasket Integrity And Possible Failure

Motor Trend expects cars to record cylinder pressures of 1000 – 2,200 psi. Gaskets have studs that secure them in place. Without those studs, they will fly away whenever a cylinder fires. The pressure can easily exceed 3,500 psi because of a detonation.

A head gasket can warp or break because engine misfires have exposed the part to uneven pressure. This outcome is more likely in cases of improper installation.

Symptoms Of Head Gasket Issues:

While you can drive with a blown head gasket, the practice is discouraged because of the damage it does to the engine. Therefore, you should learn to identify the symptoms of a blown gasket. This allows you to park the car and seek professional assistance before it’s too late.

Identifying Key Signs Indicating A Blown Head Gasket

  • The engine will overheat. The temperature gauge will let you know. Although the engine can overheat for various reasons. Look for other signs before blaming the gasket.
  • White smoke will billow from the exhaust because the coolant is invading the combustion chamber and burning. You will notice a sweet scent. Antifreeze has a sweet fragrance. The smell will confirm that antifreeze has infiltrated the oil.
  • Coolant levels will fall because the coolant is leaking. But again, the coolant can leak for numerous reasons. Don’t point the finger at the gasket until you’ve, at the very least, inspected the hoses, water pump, and radiator for leaks.
  • The oil will take on a milky texture because of the coolant.
  • You will observe a reduction in power because of a loss of compression.

Correlation Between Symptoms And Thermostat-related Overheating

The gasket will blow because of excess heat. The question is whether the excess heat originates from the thermostat or other factors. A thermostat can cause overheating by getting stuck in the closed position, which prevents the coolant from flowing.

Once the coolant refuses to flow, the heat will increase, destroying the gasket. However, thermostat-related overheating manifests similar symptoms to overheating that occurs for other reasons.

For instance, the gasket can blow because of low coolant levels, worn-out belts, a broken water pump, a corroded radiator, etc.

To prove that a bad thermostat is at fault, test it with a multimeter.

You can also retrieve the thermostat to determine whether the valve will open in hot water. If it refuses to open, the thermostat is stuck in the closed position. You should replace it.

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