Spotting Intake Manifold Gasket Problems

March 20, 2025

7 min read

March 20, 2025

7 min read

Your engine is a complicated machine. But in essence, it’s just a big air pump. Air is pulled in through the throttle body, directed to each cylinder through the intake manifold, compressed by the piston, and “boom!” goes the gasoline. That combustion drives down each piston, which moves the rest of the pistons in sequence.

With all this air rushing around, everything must be perfectly and properly sealed. For the air coming in, an intake manifold gasket is used to seal the connection between the engine and the intake. When extra air gets in (or out) through a gasket leak, everything changes. Your engine can’t perform like it should.

Intake gaskets seal the intake manifold to the cylinder head. This seal is critical for correct operation. When when it fails, you need to replace the intake manifold gasket immediately. Catastrophic damage can occur if you let a leak continue.

Intake Gasket Design

A close-up view of an engine with a melted intake manifold gasket. — This intake gasket melted due to an incompatible coolant. This was very common in certain engines in the late 1980s through the 1990s. This engine had a massive coolant leak, which nearly killed it.

Before the mid-1980s, most intake manifolds had water jackets. They allow engine coolant to pass from the engine block to the radiator hose. If those intake gaskets fail, the engine can lose coolant and overheat. Most of these engines used paper gaskets, which are fine. However, many engines in the mid-1980s through the 1990s used plastic gaskets with silicone sealing rings. These plastic gaskets cause problems. The newer coolant (OAT) type eats this plastic, resulting in a potential engine failure.

Modern intakes do not have water jackets, simplifying the gasket design and reducing their effects on cooling. Most modern engines use O-rings or silicone-sealed composite gaskets, while a few others use multi-layered steel (MLS) gaskets. They also can fail around the cylinder seals.

Symptoms of Failure

A close up view of an intake manifold gasket that has begun to fail, displayed on a metal work surface. — This gasket from the same engine as the previous image was beginning to fail around the intake port seals.

When an intake gasket fails, there are clear signs. First, your check engine light (CEL) lights up on the dash. Expect to see codes that point to lean conditions, misfires, and other emissions-related codes. These codes pop up because more air is entering the engine than the car’s computer brain knows about.

Coolant leaks can also indicate an intake leak. Look for coolant around the intake or puddling on the engine cradle. You might even spot coolant under the vehicle.

You might notice issues while you’re driving. Listen for misfires, hard starts, rough idle, surging at idle, and higher than normal engine rpm. A hissing or whistling sound from the top of the engine is a sign of a failing intake manifold gasket.

A failed intake gasket can allow water to get into a combustion chamber. If this happens, you might see white smoke from the exhaust. It mimics a blown head gasket. If you have this symptom, other tests are necessary to pinpoint the cause.

Testing for Intake Gasket Leaks

An intake manifold gasket kit for a 1999 Chevrolet Small Block 350 engine, displayed on a metal work surface. — A typical intake gasket kit comes with the necessary gaskets to complete the full job. This is the replacement gasket set for a 1999 Chevrolet Small Block 350. Note that the base gasket material is steel and not plastic like the originals.

There are multiple ways to check for intake manifold gasket leaks, but one tried and true method is to use a can of carburetor cleaner. With the engine running, open the hood and locate the intake manifold. It’s on top of the engine. Find where the intake bolts to the manifold. This is the seal you need to test. Attach the supplied straw to the can and simply spray the cleaner along all the edges of the gasket seal. You don’t need to fog it; just light spray tells the tale.

Listen if the engine rpm picks up. (It will be noticeable.) If it does, then you found your leak. If the engine rpm stays the same, there’s some other problem.

The carb cleaner trick is also great for finding other vacuum leaks. Other tests include a smoke machine and pressure testing, but those require specialty tools.

Don’t Drive With a Bad Intake Gasket

A mechanic wearing black nitrile gloves stands behind an early 2000s Honda V-6 engine, with the intake manifold and left-side cylinder head removed. — This early 2000s Honda V-6 has a very complicated intake design with several gaskets. Instead of fiber, this engine uses multi-layered steel (MLS) gaskets, which are incredibly reliable.

Technically, you can drive with a bad intake gasket. But it depends on the nature of the leak. Sometimes, the leak is bad enough that the engine will not start.

In other cases, you might experience what’s called engine runaway. That’s a violent and uncontrolled rpm increase. It’s not a good idea to drive your car with a bad intake gasket. Aslo, if water gets in through that leaky gasket, there’s a strong chance that your engine will overheat. That can cause a blown head gasket or worse.

Fixing a Bad Intake Gasket

A close-up view of a mechanic wearing a nitrile glove installing teal-colored O-ring intake manifold gaskets on a modern engine. — O-ring manifold gaskets are typically replaced any time the intake is removed.

Replacing the intake gasket on most vehicles is not quite as easy as a brake job or changing oil, but it’s not hard. It’s an intermediate-level project on most engines.

Older engines with distributors that go through the intake manifold are more difficult, because you have to remove the distributor and often re-time the engine. Newer engines with electronic fuel injection don’t have distributors, so this is not an issue. Check out our article and video on how to replace an intake manifold gasket here - opens in new window or tab. for step-by-step instructions.

Most modern engines made from the early 2000s and newer use O-ring type gaskets, which are much more stable and rarely break down unless subjected to harsh conditions.

What do you need to replace the intake gasket?

Typically, the intake is at the top of the engine, making it easy to access. Intakes are on the side in an inline engine. You may need to replace a few other gaskets when you do this job, such as valve covers or throttle body - opens in new window or tab. gaskets. In some cases, you may have to remove other components to remove the intake manifold. However, for the most part, the intake is pretty easy to reach.

Don’t delay when you suspect your intake manifold gaskets are failing. Catching it quickly reduces the potential engine damage and saves money in the long run. You can find intake manifold gasket sets for your vehicles quickly by using the eBay Parts Finder - opens in new window or tab. . Enter your vehicle’s year, make, model, engine, and trim to find gaskets designed to fit your engine’s intake manifold.

About the author

Jefferson Bryant

A lifelong gearhead, Jefferson Bryant got his first car when he was two: a Fisher-Price convertible. An industry veteran for over 30 years, Jefferson started in car audio, working his way up to product designer for Rockford Fosgate. He has written nine books and countless magazine articles about automotive technology. Jefferson also produces tech videos on YouTube. His pride and joy is a 1971 Buick GS Convertible with a swapped Procharged Gen V LT1, which he used to drive his newborn kids home from the hospital.

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This article is meant to provide general guidance only. Automotive maintenance, repair, upgrade, and installation may depend on vehicle-specifics such as make and model. Always consult your owner's manual, repair guide for specific information for your particular vehicle and consider a licensed auto-care professional's help as well, particularly for advance repairs.