The Top 5 Symptoms of an Exhaust Manifold Leak — And What to Do about Them

You get in the car to head to work and that dreaded check engine light comes on. And what’s that you hear? It sounds like the engine is roaring. These are classic symptoms of a leaking exhaust manifold. 

While you may be tempted to ignore the problem until it’s time for your next oil change or tire rotation, an exhaust manifold leak can wreak havoc on your car  — and, more crucially, it can be dangerous for your health. Keep reading to learn how to identify an exhaust manifold leak and why you should repair it as soon as possible.

What Is an Exhaust Manifold?

The exhaust manifold part of the exhaust system. The car runs on fuel, which gives off harmful gasses. The exhaust manifold’s job is to collect these gasses as they travel through the engine cylinder head and direct them to the catalytic converter, which is responsible for converting the gasses into less-harmful gasses that will release into the air.

Exhaust manifolds are connected directly to the engine block. V-type or flat engines will have two exhaust manifolds, with one on each side of the cylinder bank. On inline or straight engines, there’s only one exhaust manifold, located between the engine cylinder head and the catalytic converter.

Top 5 Signs of an Exhaust Manifold Leak

When you get in the car, you may notice strange noises or odors, or everyone’s least favorite sign of trouble: the check engine light. 

While it’s tempting to just turn up the music and roll down the windows to delay a visit to the mechanic, an exhaust manifold leak is not something to ignore or take lightly. Don’t delay exhaust repairs. The following signs could point to a leaking exhaust manifold, so if you notice one or multiple of these symptoms, make an appointment ASAP.

1. Noisy Engine

One of the clearest indicators of an exhaust manifold leak is strange noises coming from the engine. The engine might sound louder than usual as the gasses escape, or you may notice a tapping noise. The ticking or tapping sound happens right after turning on the car. As the exhaust manifold expands, it may close off the leak, and the noise will stop until the next time you start up the car.

2. Exhaust Smells

If you smell exhaust or other gasses in the car, even with the windows rolled up, this may mean the exhaust manifold is leaking. But keep in mind that a leak may also release harmful and odorless carbon monoxide into the car. 

As you breathe in carbon monoxide, the body replaces oxygen in the red blood cells with carbon monoxide, which can cause serious, lasting damage and can be deadly. If you have a headache while driving or feel weak, dizzy or nauseous, pull over, turn off the car, and step out to get fresh air immediately.

If you notice this sign of an exhaust manifold leak, consider having the vehicle towed to the repair shop rather than driving it any farther.

3. Reduced Fuel Efficiency

If you can’t travel as far on a full tank of gas as you could last month, a leak in the exhaust manifold could be to blame. The leak causes oxygen sensors to misread the engine as having a lean mixture; the electronic control unit (ECU) then increases the amount of fuel to compensate.

4. Poor Vehicle Acceleration

Similar to the way an exhaust manifold leak can lead to lower fuel efficiency, it can also make it more difficult for your car to accelerate. It may be a subtle change at first, but the longer you wait to get your car checked out, the worse the acceleration can get. This will make driving not only more difficult but also more dangerous.

5. Check Engine Light

The leak may also cause the car sensors to trigger the check engine light, so keep an eye out for this helpful symbol that may tell you something is wrong with the exhaust manifold.

Potential Causes of an Exhaust Manifold Leak

When an exhaust manifold leaks, there are a few common reasons, all of which are due to the way the engine heats up when the car is running and then cools down dramatically when the car isn’t in use.

Thermal stress. As part of the engine’s exhaust system, exhaust manifolds put up with a lot of heat, literally, every time you drive. Then they cool down considerably when the car isn’t running. All this expanding and contracting can wear down the metal over time, causing it to crack and leak.

Worn-out gaskets. To seal the space between the exhaust manifold and the engine block, gaskets help keep gasses from leaking out. The temperature changes also cause the gaskets to wear out over time, and eventually, they will fail and need to be replaced.

Broken bolts and studs. Bolts and studs can become brittle due to those extreme temperature changes from hot to cool when the car is running versus not running. If they break, they can cause a leak.

When (and Why) to Repair or Replace a Leaking Exhaust Manifold

A leaking exhaust manifold needs your attention as soon as possible. Because this part is crucial to moving toxic gasses from the engine to the catalytic converter — and ultimately out of the tailpipe as less harmful gasses — a leak can be serious trouble. If the gasses leak into the cabin of the car, you and your family will be exposed to carbon monoxide (which can be lethal), as well as volatile organic compounds and other hazardous gasses.

Aside from putting your health at risk, the leak can cause more damage over time to other parts of the car. The exhaust valves can get burned, the leak can damage oxygen sensors, or the problem can cause the catalytic converter to fail prematurely. It may also increase your fuel consumption, meaning you spend more on gas each week.

This is a job best left to the pros since a leaking exhaust manifold can be dangerous. With multiple potential causes for a leak, a pro can quickly identify and remedy the problem.

An exhaust manifold leak is serious and can put your family’s health at risk, so you’ll want to take your vehicle to a trusted local auto repair shop for repair or replacement immediately. 

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