Exhaust Manifold Leaks – Function, Failure symptoms, Potential damage.

Exhaust Manifold Leaks - Function, Failure symptoms, Potential damage.
Exhaust Manifold Leaks - Function, Failure symptoms, Potential damage.

Exhaust manifold leaks can be dangerous, as well as cause other costly problems.

So, the function of the exhaust manifold is to; collect the exhaust from each cylinder and combines it into one pipe.

Because, it is bolted directly to the cylinder head; it is the first line of defense, from hot and dangerous gases. Once these gases exit to the rest of the exhaust system, the exhaust manifold has done its job.

But, if there is a crack or any exhaust manifold leaks, the whole exhaust system is affected. When gases come out of the engine, they are extremely hot. But, they do cool gradually, as they reach the tailpipe at the back of the vehicle.

Visual Crack On Exhaust Manifold
Visual Crack On Exhaust Manifold

So, if you smell exhaust from the engine compartment and hear a ticking noise; you could have a leak. Over time, the gases leaking from a manifold, will damage surrounding components.

If you think you have a leak, always start with a visual inspection. Look for black soot around the manifold and downpipe connection.

Exhaust Manifold Leaks, Will Produce A Few, Failure Symptoms:

  • Excessive, engine noise.
  • Decrease in power, acceleration, and fuel efficiency.
  • Burning smell, coming from the engine bay.

Exhaust Manifold Leaks, Can Be Caused By:

  • A cracked manifold.
  • Leaking gaskets.
  • Loose or broken bolts or studs.

Cracked, Exhaust Manifolds

Leaks in a manifold are often cracks in the metal, due to the intense temperatures of the engine. Cracks may start out as small as a hairline crack; which may be noticeable, when the vehicle is first started. Once the manifold heats up quickly; the crack, might self-seal, as the metal of the manifold expands.

Visual Crack On Exhaust Manifold
Visual Crack On Exhaust Manifold

As a result, the noise coming from the crack, then becomes less noticeable. However, over time; the hairline crack will begin to increase in size, due to constant heating and cooling.

Leaking, Manifold Gaskets

The gasket is another area of concern, that has to sustain the expanding and contracting of the heated metal. Its failure symptoms, are similar to the cracked manifold and could inevitably become a larger problem.

Exhaust Manifold Gasket Leaking
Exhaust Manifold Gasket Leaking

Exhaust manifold gaskets are very important; as they are the main gasket, that seals the entire exhaust system. So, when the exhaust manifold gasket; or gaskets fail or have an issue; it can cause problems, with the performance and drivability of the vehicle.

Loose Or Broken, Bolts Or Studs

Sometimes an exhaust manifold starts to leak, because a mounting bolt or stud has broken. Exhaust manifold bolts and studs, both suffer the same fate; of getting brittle from too many heating and cooling cycles. Along with expansion and contraction of the whole system, something has to give.

Broken Bolts In Cylinder Head
Broken Exhaust Manifold Bolts In Cylinder Head

Consequently, making broken bolts or studs, a fairly common problem. Not to mention, the repair for this, can be a nightmare as well. The good news today is, there are better tools and techniques, for making this repair easier.

Potential Damage, Caused By Leaks Include:

  • Burned, exhaust valves.
  • Improper fuel trim  (as the leak introduces extra oxygen that is picked up by the (O2) oxygen sensor ).
  • Slow warm-up time  (which also causes, high fuel consumption ).
  • Catalytic converter to fail prematurely.
  • Sensors ((O2) oxygen sensors).
  • (EGR) Valve function.

So, these factors all depend on, where the leak is located in the exhaust. The further away from the engine and the catalytic converter the leak is; the less chance damage can happen.

Leaking Gasket
Leaking Exhaust Manifold Gasket


So, if your exhaust manifold has a leak; it will have an impact on, the pressure in the exhaust system. As a result,  reducing fuel economy and leading to, higher emissions. Finally, if a leak develops in the exhaust close to the engine; this can have a, big impact on fuel economy.

Thank You !