Why Do Exhaust Manifold Bolts Break? (Solved)

Exhaust manifold bolts can be prone to breakage because of how hot they can become due to heat exposure while running your vehicle.

They are vital for the manifold’s smooth performance, so any bolts’ breakage may have serious problems with the entire functioning of the exhaust system.

The bolts hold the exhaust manifold in place, so drivers should regularly check their manifold bolts to ensure they are in good shape and always replace any broken bolts as soon as they notice any breakage.

Today, we shall explain why exhaust manifold bolts break and how to prevent that from happening.

We shall also go deeper and expound on what happens if the exhaust manifold bolts break, among other informative topics. Let’s get started.

Here Is Why Your Car’s Exhaust Manifold Bolts Could Break

Your car’s exhaust manifold bolts usually break as a result of constant exposure to heat. The bolts are typically made to cope with very extreme temperatures. However, they cannot withstand this for a longer period due to rust and corrosion. As years go by, your manifold bolts will start to deform and finally break. That’s why it’s usually recommended that drivers should be vigilant of their bolts to prevent breakage from happening.

Car exhaust manifold bolt removal
Car exhaust manifold bolts removal

Another reason for manifold bolt breakage is that bolts made from steel may lose strength when frequently exposed to very high temperatures.

Exhaust manifold bolts are made to last longer, but eventually, they will break because of extremely high temperatures. The high heat usually causes seizing, galling, and corrosion, leading to breakage.

Other metals like titanium exhaust manifold bolts and the case of soft aluminum also may get broken when in contact with high heat, cold, and debris. That’s why it is advisable to check your manifold bolts and clean any waste for the smooth functioning of the entire component.

The two reasons are extremely risky, especially when the gasket is being replaced and the manifold bolts break because of loss of strength; you will spend more to repair the damage.


How Can You Prevent Exhaust Manifold Bolts from Breaking?

Car exhaust manifold nuts and bolts corroded
Car exhaust manifold nuts and bolts corroded

One of the good ways to prevent exhaust manifold bolts from breaking is using an anti-seize. It is a product you apply to your bolts to prevent corrosion, seizing, and galling, which usually cause the manifold bolts to break with time.

An anti-seize lubricates your manifold bolts, making them stay longer without breaking. A properly selected anti-seize will do the following to your bolts.

  • Reduces pick-up and galling when you want to assemble your manifold.
  • Prevent corrosion and any chemical attack that usually affects the manifold bolts.
  • Prevents any damage to the manifold and bolts.
  • It offers easy dismantling hence minimizing any chances of damage.
  • Lubricates and separates the bolts connecting the joints during operation, minimizing any loosening, wear and tear.
  • It provides a consistent and precise clamping force for the manifold bolts.

You have to apply a thin layer of Loctite or anti-seize to your manifold bolts using a brush, and your bolts will be secure.

Other prevention measures include:

  • Use only a little force when removing the bolts. You can use sprays or lube oil to make removal much easier.
  • Before you fix the manifold bolts, wipe the holes first and remove any debris or overstayed oil so that it does not accumulate inside the holes.
  • You can use lubrication oil to lubricate the manifold bolts before inserting them.
  • When placing the bolt, tighten it using a wrench and ensure you do not overtighten or under-tighten the bolts. Use the correct torque option.
  • If you notice the bolt is stuck, do not forcefully press it down. Use an appropriate tool to remove it well.

What Happens If the Car’s Exhaust Manifold Studs or Bolts Break?

If the car’s exhaust manifold studs or bolts break, they usually cause problems to the manifold. First, they will cause a ticking sound, especially when your engine is cold. The broken bolts generally make the manifold drive in unwanted gases, leading to a ticking sound.

When there is a temperature rise in manifold bolts, the manifold will expand and reduce the ticking noise. However, this will affect your vehicle’s performance and safety because harmful gases will leak into your cabin, leading to headaches and nausea, which are signs of carbon monoxide poisoning.

Other possible things you may notice if the exhaust manifold bolts break are as follows:

Exhaust Smell

As mentioned above, if there is a breakage of any of the manifold bolts, harmful gases may leak instead of flowing to the catalytic converter. So, each time you open your hood, you will sense a strong exhaust smell, especially towards the exhaust manifold.

Reduced Power

Breakage of the manifold bolt will lead to loss of backpressure, which impairs engine performance. Some drivers may notice a sudden power reduction, especially during accelerating.

Depending on your car type and the engine’s design and ancillaries, you have to check your manifold bolts keenly.

No matter how small the breakage is, it will be best to have an expert mechanic thoroughly inspect the entire manifold before the damage becomes severe.

Should I Frequently Replace Exhaust Manifold Bolts?

It is highly recommended that you replace your exhaust manifold bolts frequently. You can do this alone or with the help of a mechanic for a smooth process. You can use a wrench or spanner to help you tighten the bolts as required.

Can You Get Special Types of Exhaust Manifold Bolts That Don’t Break?

The special types of exhaust manifold bolts that don’t break often are those made from stainless steel. They do not rust easily except when using them on iron threads or stainless-steel exhausts. They function well in various conditions and temperatures.

Other divers usually use bolts made from iron, a cheaper option specially used in old manifolds. You will find steel bolts in different grades for you to choose from.

Here are the different types of bolts you can see in the market:

Manifold BoltManifold Bolt Description
12X M8 HEX Copper Manifold BoltThis manifold bolt type usually comes in 12 pieces. It is made up of carbon steel and it’s also copper plated. It has a 10mm internal thread diameter, which is convenient and durable.
Akazon M8 Manifold BoltsAkazon M8 manifold bolts are made from high-quality 304 stainless steel metal. The 304 stainless steel does not easily rust and corrode. Durability is guaranteed. In addition, you get high performance, and they are precise and worth your trust.
Kimis 1 Stainless Steel BoltsIf you want comfort, then Kimis one stainless steel bolts are good for you. They are of superior quality and give flawless performance and durability. Also, installing them is faster. You don’t have to do any modifications, drilling, or cuts.

How Much Does It Cost to Fix and Replace Exhaust Manifold Bolts?

The price usually varies between mechanics for fixing and replacing exhaust manifold bolts. There is no standard fee. It all depends on the work that has to be done and the hours the mechanic will spend fixing and replacing manifold bolts.

The replacement may take between two to three hours. Also, this depends on how fast you or the mechanic is.

The process may take longer if there is some maintenance or repair that needs to be done.

Can I Weld the Exhaust Manifold Instead of Using Bolts?

Yes, you can weld the exhaust manifold instead of using bolts. Most people usually prefer using a MIG welder for the welding process. The duration of welding will be lengthy since the temperature must be cool inside your exhaust manifold for safety purposes. Also, you will have to be careful while welding, especially in those limited access low-vision manifold areas.

Here are some pros and cons of welding the exhaust manifold. Take a look.

The Pros

  • It is relatively affordable and quicker when you have the right knowledge.
  • You get more rigid joints.

The Cons

  • You need to possess knowledge of heat transfer and welding.
  • Not 100 percent efficient.
  • It takes a lot of time to weld, from equipment setup to heating and cooling the welded part.
  • Most current engines come with dissimilar metals making welding a challenge.

The good thing about using bolts is that when you want to inspect the joints, it will be easier than welding.

The only problem is that fixing the bolts requires time and patience; in case of damage, you will have more work. However, that should not scare you. You can still weld or use the manifold bolts. The choice is yours.


The main reason for manifold bolt breakage is their exposure to high temperatures while the vehicle runs. The high heat in the manifold usually causes the bolts to corrode, weaken, and eventually break.

Luckily, we have highlighted several preventive options you can opt for to stop your manifold bolts from breaking. If they continue to fail, you can contact an expert mechanic to help diagnose and solve the problem.


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