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Mustang Gasket Tech Guide

Written By: Connor MC

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Finding oil in your engine bay or on the ground isn't the best way to keep your Mustang looking good or running well. Fix all of your Mustang leaks, spills and drips with new gaskets and gasket sets!

Shop Mustang Gaskets

Gaskets, despite being very light and inexpensive pieces, play an important role in regards to the overall health and functionality of your engine. The purpose of a gasket is simple – mate two surfaces together and provide a leak-free seal.

American Muscle

What are Mustang Gaskets?

A gasket is a thin, compressible, sheet-like piece made from various materials (could be cork, metals, copper, fibrous, rubber etc). The keyword is ‘compressible’ because it's this property that makes a mechanical gasket so effective at sealing two surfaces. In the automotive manufacturing world, there will be a difference between mating surfaces. This difference is typically between hundreds-of-an-inch to thousands-of-an-inch, which although very little makes a big difference during the strains and stresses of combustion engine. When you throw a gasket in between these surfaces and bolt them together, the gasket is squeezed and compresses to fill in gaps that are present. When working on an engine, make sure you adhere to the torque specs so the gasket can do its job how it was designed.

Gasket material and construction play a role as well. As mentioned, gaskets can be made of cork, multiple layers of thin metals, rubber or silicone based, fibrous, or any combination of the above. Gaskets can be one piece, two-piece, or more. A simple analogy to think of is a grilled cheese sandwich. When the cheese warms up, I press down on the top of the sandwich with a spatula. The result - the cheese compresses and fills all the space between the two pieces of bread making a delicious lunch! This isn’t the most scientific of analogies, but it should give you the right idea.

Mustang Exhaust Pipe Gasket

Where are these gaskets, and how do I tell if they need replacing?

We know what a gasket is, but where are they? Frankly, they are all over your Mustang’s engine! Pretty much every metal-to-metal mating component uses a gasket, as well as any place where fluid transfer occurs. The gaskets that you should familiarize yourself with are

  • Oil pan gasket 
  • Cylinder head gasket 
  • Valve cover gasket 
  • Intake manifold gasket
  • Exhaust gaskets

There are numerous others, but all on that list above are on the should-know-basis. Let us examine each one a little more closely.

Mustang Shifter Gasket

Oil pan gasket

This gasket seals the oil pan (where the oil is contained) to the bottom of the block. Without it, oil would seep or spray out as the engine runs. Older Mustangs used a 2-piece, combination cork and rubber gasket, whereas later model Mustangs use a one-piece design.

Diagnosing this gasket is pretty easy. If it is no longer sealing, you’ll clearly see oil around the edges of the pan, on the pan, even on surrounding parts (k-member). You may even wake up to find a nice puddle of oil under the car. In the event you run into any of these symptoms, unfortunately, swapping the gasket is not easy. Usually, the motor at a minimum needs to be lifted off the mounts to give enough clearance, but if you’re going that far, you might as well have the entire motor lifted out.

Oil Pan Gasket

Valve cover gaskets

These gaskets are located underneath the valve covers and prevent any oil from dripping out from under the valve covers and onto the block. They are a one piece, metallic design. Oddly enough, some oil weeping from the valve covers is acceptable, particularly on older engines (pushrod engines). If you need to replace these due to excessive oil leaking, luckily valve cover gaskets are one of the easier ones to replace. You just need to get the valve covers off (sometimes, this may include taking the intake off as well), and presto, you have immediate access.

Valve Cover Gasket

Intake manifold gasket

The intake manifold gasket fits between the lower intake manifold and the cylinder heads. Its purpose is to seal the intake manifold to the head, prevent coolant from entering into the combustion chambers, and also to prevent excess air from entering the engine. If you hear a whistling sound near the intake, see residue around the intake manifold or have coolant loss, the intake manifold gasket could be shot. Replacing it involves removing the entire manifold, cleaning the surfaces, and slapping the new one back on.

Mustang Intake Gasket

Cylinder head gaskets

Often referred to simply as head gaskets, the cylinder head gasket plays a major role in the overall functionality of your motor. The head gasket seals the cylinder head to the block, but it also helps maintain compression and prevent oil or coolant from entering into the combustion chamber. A broken head gasket can greatly affect your engine. Depending where it is broken, it can greatly lower compression on a cylinder or multiple cylinders, it may lead to the introduction of coolant and oil into your cylinders (not good!), or even cause backfiring. Excessive smoke out of the tail pipes (blue or white), poor engine performance are common symptoms of a blown head gasket. Simple diagnostic tests involve a compression test, or even better, a leak-down test.

Replacing these is a chore, but crucial to engine performance. The entire top end of the motor has to come off to access these, and picking the right replacement can be tricky as well. Depending on your motor setup (compression ratio, naturally aspirated or forced-induction), stock head gaskets may not be for you. You may need some that are stronger in relation to the type of motor you have built. 

Mustang Cylinder Head Gasket

Exhaust manifold gasket

The final gasket to be examined is the exhaust manifold gasket. It seals the exhaust headers to the exhaust port on the cylinder head. This gasket is one of the few dry gaskets, meaning it does not seal against liquid (there are no fluids flowing between the headers and the exhaust ports). It ensures that no exhaust escapes between the exhaust port and the header flange. A leaking gasket will be immediately noticeable, as your exhaust note will greatly change (usually very raspy and loud), and you may notice more powerful exhaust fumes in the cabin.

Exhaust Manifold Complete Gasket Set

Gaskets A Plenty

All being said, the gaskets that are installed all throughout your Mustang have an important role. Some are more pivotal than others (like the head gasket), and despite being a cheap part, have a very tough job. Like all components, as they age and the heat cycles and build up increase, engine gaskets deteriorate and begin to leak. There isn’t a definite period to say when this will happen, unfortunately. The best way to keep everything under control is to do a regular visual inspection.

Mustang Gaskets
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