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5 Signs of a Cracked Exhaust Manifold and What You Can Do to Solve This Problem

Even though most exhaust manifolds are made of cast iron or stainless steel, they are not indestructible. Over time, they can crack due to constant, extreme temperature fluctuations, leading to unpleasant symptoms or even permanent engine damage.
Exhaust Smoke 7 photos
Photo: Matt Boitor on Unsplash
Ford GT TailpipesGM OEM Exhaust ManifoldGM OEM Exhaust ManifoldCracked Exhaust ManifoldExhaust ManifoldBMW M1 Engine with Visible Manifold
As an important component of an internal combustion engine, the exhaust manifold diverts gasses from the cylinders to the exhaust system. Depending on the arrangement of the cylinders, an engine may have one or two of them. In-line engines, for example, usually have one, while V-engines have two.

Cracks in these components occur, especially in older vehicles that are already heavily worn. When this happens, the engine can overheat, which can cause permanent damage. In addition, the exhaust gasses that escape through the crack can have harmful effects on the environment and your health, because in some cases they make their way inside the cabin.

We spoke with several experienced mechanics and compiled a list of symptoms that are associated with a cracked manifold. We also discussed whether a crack can be repaired, and whether it's worth it in the long run.

Strange noises - If exhaust gasses are escaping through the crack, you will hear strange noises while driving. Depending on the pressure under which the gasses are escaping and the severity of the crack, you may hear a whistling or clicking sound. Often, these noises are more pronounced when the engine is cold. So raise the hood, start the car, and listen carefully.

Cracked Exhaust Manifold
Photo: L.C. Nøttaasen on Flickr
Exhaust Smell - As mentioned earlier, if there is a crack in the manifold, some of the harmful exhaust gasses can enter the passenger compartment instead of being directed downstream to the catalytic converter or particulate filter and out the tailpipe.

When you open the hood, you will often notice a strong exhaust smell, especially around the manifold.

Loss of power - A crack will result in a loss of backpressure, which will noticeably affect engine performance. In most cases, there is a sudden loss of power, especially when accelerating.

Increased Fuel Consumption - In addition to the noticeable loss of power, the loss of back pressure can also have a negative impact on fuel consumption which can increase exponentialy.

Visible Cracks - Depending on the vehicle and the arrangement of the engine and ancillaries, you may be able to inspect the manifold(s) yourself. Usually, cracks are found in the area of the bolts that connect them to the cylinder head. This is the area that is exposed to the highest temperatures.

However, small, thin cracks are almost invisible to the naked eye, so it's best to have the component inspected by a qualified mechanic.

GM OEM Exhaust Manifold
Photo: ACDelco

What To Do

First of all, some of the symptoms may also be caused by a damaged gasket, in which case you obviously do not need to replace the entire manifold. That's why it's important to have the problem diagnosed by a professional. However, if you go to a dealership, they won't bother with repairs regardless of how small the crack is and will suggest an OEM replacement part that may cost more than your car.

To avoid this, we strongly recommend that you visit a garage that specializes in exhaust system repairs, where experienced mechanics can assess if the crack is fixable or if the manifold really needs to be replaced. They have the experience and ability to braze or weld the manifold if the crack is small.

This will solve the problem for less money, but do not expect the patched part to last as long as a new one. All mechanics agree that the best long-term solution is replacement, and you can opt for an aftermarket component that usually costs much less than an OEM part.
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About the author: Vlad Radu
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Vlad's first car was custom coach built: an exotic he made out of wood, cardboard and a borrowed steering wheel at the age of five. Combining his previous experience in writing and car dealership years, his articles focus in depth on special cars of past and present times.
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