Blog Car Care Advice 5 Symptoms of an Exhaust Manifold Leak (+ ls It Safe to Drive?)
Car Care Advice

5 Symptoms of an Exhaust Manifold Leak (+ ls It Safe to Drive?)

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Troubled by unusual sounds, reduced engine performance, or sluggish response to the gas pedal input?

It could be an exhaust manifold leak.
But how can you be sure?

Let’s explore the main symptoms of an exhaust manifold leak, how to deal with it, and whether it’s safe to drive with the leak.

This Article Contains:

Let’s go!

5 Common Symptoms of an Exhaust Manifold Leak

Here are some evident signs that your car’s exhaust manifold may be leaking:

1. Unusual Noises

You may hear a ticking or tapping sound that can seem like a strange engine noise. However, it’s likely due to gases leaking through the exhaust manifold.

These sounds will be more prominent when the engine is cold than when it warms up. This is because a crack in the manifold gets smaller when exhaust gases heat the metal, expanding it, and the leak gets reduced.

2. Exhaust Smell in the Engine Bay

A damaged exhaust manifold or gasket will leak exhaust fumes, leading to an exhaust smell in the engine bay or cabin. These exhaust fumes can be harmful as they contain toxic carbon monoxide. 

You may also notice a burning smell if the hot exhaust gas burns a plastic part or wire in the engine bay.

Note: Exhaust gas leak from a point before the catalytic converter will contain higher concentrations of carbon monoxide than what’s emitted from your vehicle’s exhaust pipe. This contributes to environmental pollution.

3. Sluggish Acceleration

A leaky exhaust manifold can negatively affect the removal of exhaust gases from a cylinder (exhaust gas scavenging), causing a buildup within the engine. This will reduce the combustion efficiency and result in reduced engine performance, evident as sluggish acceleration when you press the gas pedal.

4. Poor Fuel Efficiency

A cracked exhaust manifold can allow air to enter the exhaust system, affecting the readings of the oxygen sensor (O2 sensor).

The oxygen sensor may incorrectly prompt the Engine Control Unit (ECU) to inject more fuel into the engine. This disturbs the air-fuel ratio required for efficient combustion, lowering the vehicle’s fuel efficiency.

5. Illuminated Check Engine Light

The ECU activates the Check Engine Light (CEL) if the oxygen sensor’s output is beyond the expected range. If the exhaust leak is large and the ECU injects way more fuel than required, engine misfires can occur, triggering the CEL and registering a fault code.

Now, let’s see why you shouldn’t ignore a leaky exhaust manifold.

Can You Drive with an Exhaust Manifold Leak?

You shouldn’t drive your vehicle with an exhaust manifold leak since harmful gases such as carbon monoxide can enter the car’s cabin and make you sick. In fact, high enough concentrations of carbon monoxide can be fatal.

And that’s not all.
The catalytic converter can get damaged due to excessive misfires caused by an exhaust manifold leak. Plus, a leaking manifold can cause a rich condition, resulting in malfunctioning oxygen sensors fouled by fuel.

So, if you suspect an exhaust manifold leak, get your car inspected by an auto repair professional soon to ensure your safety and prevent damage to your vehicle.

Next, we’ll explore the primary reasons for a leaking manifold.

What Are the Possible Causes of an Exhaust Manifold Leak?

Exhaust manifolds generally go bad due to:

A. Frequent Expansion and Contraction

Thermal stress from expansion and contraction as the engine warms up and cools down can result in a cracked exhaust manifold and a failed manifold gasket.

B. Loose Exhaust Manifold Bolts

If a nut or bolt (stud) securing the exhaust manifold to the engine block has come loose or is missing, the exhaust gases can leak out. An improperly installed bolt can also warp the manifold and cause it to crack.

Replacing a cracked manifold or a failed manifold gasket may be obvious. However, a mechanic will first inspect the exhaust system to find the source of the leak.

Let’s see how.

How to Diagnose a Leaking Exhaust Manifold

Here are the steps an automobile technician may take to diagnose a leaky exhaust manifold:

  1. Start the engine (it should be cold).
  1. Raise the vehicle using a jack or a car hoist.
  1. Listen for ticking or similar exhaust noise coming from under the car and try to locate its source.
  1. Spray soap solution on the exhaust manifold or any other area suspected to have a leak.
  1. Observe if the sprayed solution on the exhaust piping shows signs of the exhaust stream rushing out.
  1. Look for soot deposits or melted electrical wires around the exhaust manifold.
  1. Check if the exhaust manifold bolts and nuts are in place and not loose.

The mechanic may also remove the exhaust manifold from the vehicle to inspect it closely:

  1. Check the exhaust manifold surface, which seals up against the engine block through a gasket. If the surface is irregular with raised areas or has soot deposits, you may have an exhaust leak.
  1. Check the exhaust manifold gasket for damage and soot deposits.
  1. Check for hairline cracks on the manifold tubes and bends.
  1. Check the donut gasket between the exhaust manifold and downpipe for damage.

Note: Diagnosing and fixing exhaust leaks may require technical expertise and special tools and should be best left to a trained mechanic.

Have more unanswered questions about the exhaust manifold?
The following section can help you.

3 FAQs about an Exhaust Manifold

Here are answers to three common questions about the exhaust manifold:

1. What Does an Exhaust Manifold Do?

An exhaust manifold collects the exhaust gas from multiple cylinders, after which it passes through the catalytic converter and finally exits the vehicle through the exhaust pipe. Exhaust manifolds are designed to allow good scavenging of the burnt gas when the exhaust valve on a cylinder opens. This helps attain efficient combustion. 

Since this exhaust system component can get quite hot, it’s sometimes coated with ceramic or heat-resistant paint.

2. How Much Does it Cost to Replace an Exhaust Manifold?

Exhaust manifolds can vary in price depending on the make, model, and year of your vehicle.

Replacing a cracked manifold usually costs between $300-$2,260, with the part priced at $50-$1,210 and the labor charges ranging from $250-$660. If you only have an exhaust manifold gasket leak, you can get a new manifold gasket for $35-$75.

3. How Is an Intake Manifold Different from an Exhaust Manifold?

The intake manifold evenly supplies air to the intake ports of the engine cylinders. Its vacuum operates different systems on a vehicle, like the Positive Crankcase Ventilation (PCV) valve and brake boosters. The exhaust manifold helps with exhaust gas removal. 

The intake manifold is located at the top of the engine, directly above the engine’s cylinder head, whereas the exhaust manifold is usually attached to the engine block on the side or bottom of the engine. 

Wrapping Up

Symptoms like unusual exhaust noise and burning smell can indicate a leaky exhaust manifold on your vehicle. In such cases, get your car inspected by a mechanic soon to protect yourself from harmful gases and your vehicle from damage.

Looking for a convenient and effective way to get the exhaust leaks fixed?
Get the job done by a qualified technician from AutoNation Mobile Service.

We are a mobile auto repair service that can cater to exhaust system problems and other issues with your car right in your driveway. 

Contact us for a top-notch service experience and get a 12,000-mile or 12-month warranty on the repair.