Are you planning to replace the head gasket of your engine and you want to know if you should use a copper spray on the head gasket before installing it? You’ve come to the right place, for we have researched this question, and we have the answer for you.
It depends on the type of head gasket. A type of head gasket can benefit from a layer or two of copper spray. However, it is completely useless to another type of head gasket. For example, it can be useful on a copper head gasket, useless on an elastomeric head gasket, and harmful to an MLS head gasket.
Let’s talk more about why a copper spray on a head gasket can become useless to one and useful to another in the succeeding sections. Learn more about head gaskets in the sections below.
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What Are The Different Types Of Head Gaskets?
We will look closely at the different types of head gaskets in the following sections. Knowing the properties of the different types of head gaskets will allow us to examine if there is a need for an additional sealant like a copper spray before installation or not.
A head gasket is not one size fits all. Each gasket is made for a specific engine make and model. You cannot get a head gasket that is made for a specific engine, then modify it so that it will fit into another engine.
In addition to fitting a specific engine, there are specific properties that head gaskets should have to become effective. These materials used in head gaskets have these properties, making them ideal for use as head gaskets. These properties are:
- Resistance to pressure
- Resistance to extreme temperatures
- Resistance to chemicals
Let’s look at each attribute in greater detail below.
This is the property of a head gasket to conform to the surface imperfections of the engine block and cylinder head. Conforming to the surface roughness allows the head gasket to create a tight seal.
Without this property, a head gasket will have a leak on every imperfection on the mating surfaces of the engine block and cylinder head. A material with low malleability will need a very smooth surface to make a good seal.
Resistance To Tensile Stress
One of the primary functions of a head gasket is to seal the enormous pressure that comes from combustion. The tensile strength of the head gasket must be enough to resist tensile stress from the engine.
Tensile stress is a type of force that tears a material apart. The combustion inside the engine generates forces that the head gasket must be able to contain within the combustion chamber.
The constant combustion of fuel and air inside the engine generates forces that constantly pound the head gasket. Thus, it should have enough tensile strength to resist damage from the effects of combustion.
Resistance To Extreme Temperatures
Head gaskets should be able to retain their structure and properties during extreme temperatures.
It should be able to resist below-freezing temperatures during winter. Similarly, it should also be able to resist up to 500 degrees when you drive at noon in the summer.
The cylinder head should be able to survive multiple cycles of extreme cold and extreme heat and retain its sealing properties.
This is the property of the head gasket to resist leaks from liquid and gas inside the engine.
Oil and coolant are fluids that constantly move inside the engine to keep the engine running in great condition. However, this also means that these two fluids are constantly checking every minuscule section of the gasket for a way to get out of the engine or into the combustion chamber.
The same goes for the exhaust gases that the combustion generates at the end of each cycle.
Resistance To Chemicals
All the above properties are useless if the head gasket corrodes or breaks down under constant exposure to coolant, oil, fuel, and combustion by-products. It should resist the corrosiveness of these compounds and maintain its properties to be effective as a head gasket.
What Are The Different Types Of Head Gaskets?
Composite Head Gasket
This is commonly known in the past as a “paper gasket.” It is made of fiber, bits of foil, rubber, and silicone compressed together into a thin plate. It is a cheap type of gasket that has high availability.
It has a metal ring around the cylinder area to create a better seal for the combustion area. It can accommodate rough finishes on both the engine block and the cylinder head.
However, a composite head gasket has a shorter lifespan than most modern head gaskets today. Moreover, they are effective only for low-output engines, having very limited effectiveness in keeping the combustion forces from a high-output engine.
MLS Head Gasket
An MLS or a multi-layered steel head gasket is one of the most popular head gaskets in modern automobiles. This type of gasket is made of several layers of steel sheets held together with elastomer. Its surface has a coat of corrosion-resistance layer.
Steel, an alloy of iron and carbon, is known for its strength and resistance to chemicals inside the engine. The coating of an MLS head gasket makes it even more ideal as a head gasket for engines.
On the downside, the quality of an MLS head gasket can vary greatly between manufacturers. High-quality MLS head gaskets are really good, while low-quality MLS can give you headaches.
Another downside is that it needs a really smooth surface to provide a good seal because of its low malleability. It is important to note that there should be no supplementary sealer—like a copper spray—on the head gasket or the surfaces of the block or head.
An MLS is sensitive to the smallest deviation in smoothness, and this deviation can lead to a leak in the seal. A supplementary sealer will make the surface less smooth because the layer of copper will never be a perfectly smooth layer against the engine block and cylinder head surface.
Thus, a copper spray on an MLS head gasket can lead to shorter service life and earlier leaks. It will not help improve the seal.
And this goes for any type of sealant, not just the copper spray.
A Subaru MLS Head Gasket Kit is available on Amazon through this link.
Copper Head Gasket
Copper head gaskets are cut from a solid copper sheet. This gives it more strength than a composite head gasket like the MLS.
Copper is naturally malleable. Its strength as a single-piece material and its malleability make it the head gasket of choice for performance cars.
A copper head gasket can be difficult to install, however.
A copper head gasket performs better with a stainless-steel O-ring around the combustion chambers. However, a professional must machine the engine block to create the grooves that will hold the O-rings in place.
The same machining should be done on the cylinder head to match the grooves for the O-ring. The combination of a stainless-steel O-ring and a copper head gasket creates a strong seal against high pressure that other types of head gaskets are unable to match.
The complexity of the installation of a copper head gasket makes it popular only with professional drivers and high-performance cars.
Another downside to the copper head gasket is the water leak. A water leak is almost always inevitable with a copper head gasket. Thus, you should apply a layer or two of copper spray on both sides of a copper head gasket.
Leave the copper spray layer to dry for 15 minutes to half an hour before applying the second coat. Allow the second coat to dry for the same amount of time before you install the copper head gasket.
Elastomer Head Gasket
An elastomer head gasket or elastomeric head gasket is similar to an MLS head gasket. The only difference is that an elastomeric head gasket has only one layer of steel, while an MLS head gasket has two to five.
An elastomeric bead is then applied to the surfaces of the steel core. The elastomeric bead helps create a tight seal between the engine block and the cylinder head.
The layer of elastomeric bead is thicker than the layer of an MLS head gasket and it is on the surface layer. This gives the elastomeric gasket high elasticity. They compress very well and conform to any imperfections in the surface of the engine block or cylinder head.
One of the properties of an elastomeric head gasket is its ability to maintain its elasticity even when under compression, below-freezing temperatures, extremely high temperatures, and exposure to chemicals.
Its elasticity is its greatest attribute, allowing it to create a seal with an irregular shape or smoothness in the mating surfaces.
Its molecular structure prevents it from becoming brittle or from melting under extreme heat. This is the same material on airplane doors and windows.
Using a copper spray on an elastomeric head gasket would be pointless since the elastomeric layer already does everything that a copper spray seal would do. Moreover, the copper spray might even hinder the effectiveness of the elastomeric seal of the head gasket.
The usefulness of a copper spray on a head gasket is dependent on the type of head gasket that is being installed. It can be useful on a copper head gasket and useless on an elastomeric head gasket while being harmful to an MLS head gasket.
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