How To Fix Exhaust Flange Leak – Top Tips For You

In general, common drivers do not pay as much attention to car details as car enthusiasts unless something unusual happens to their vehicle.

This is very dangerous because they tend to overlook small problems like leaking or weird sounds in the deep interior that ultimately lead to bigger problems.

In this article, we will focus on a particular leaking issue: How to fix exhaust flange leak.

The exhaust errors are usually the most neglected and difficult to identify due to internal leaking on the flange and suppressed noises from inside the exhaust pipes.

Scroll down this article and learn how to fix exhaust leak at flange, as well as flange repair, in full detail.

What Is An Exhaust Flange & How Does It Work?

How To Fix Exhaust Flange Leak

An exhaust flange is a pair of small metal sections that connect exhaust pipes underneath the interior of the exhaust system.

It includes two metal bands with 2 to 4 bolts that seal the exhaust gasket to prevent leakage from the metal pipes.

Modern car manufacturers use 10mm bolts for 2-bolt flanges or 8mm bolts for 3-bolt flanges in a ball-type socket.

Each of them is about 8.8 tensile or higher in order to protect the exhaust gasket from stretching or cracking. Spring washers, Loctite, or locking nuts are also used to prevent vibration.

Exhaust flanges are found in many types of exhaust, including exhaust manifolds and tubular headers.

They serve as a donut-shaped gasket to prevent exhaust leaks by sealing the exhaust sound, heat, and fumes.

Some flange bolts come with a heavy coil spring to balance the pressure in case other bolts are loosened.

If there is a leak in the exhaust flange, you should replace the old muffler flanges with new ones as soon as possible because it is a sign that they can no longer contain extreme temperatures.

They often wear down after two or three years, depending on personal driving habits such as gas pedaling, keeping the engine running for an extended time, etc. So how to fix exhaust leak at flange?

Signs Of Exhaust Flange Leak

check for exhaust leaks

The best way to check for exhaust leaks is to start the engine and let it run for a minute. There are several signs of an exhaust leak that you may find in the process:

Unusual Noise

Bad flanges will make particularly unusual noises, unlike any other parts of the car. In addition to metal clanging, you will hear hissing or tapping sounds of leaking liquid deep inside the system.

The sounds get louder the faster you drive, especially on rough terrains. It is even more irritating with some loud exhaust systems.

Fuel Inefficiency

There are many reasons for fuel inefficiency, and exhaust leak is one of them.

If the liquids are constantly leaking, the engine has to work harder to compensate for it, and you might notice that your car uses more fuel than factory new.

Foul Smells From Exhaust

Another leak indicator is the smell from the exhaust. Instead of flushing to the back, you will find a lot of fumes floating as you start the engine, with a scent of nitrogen and dust.

Occasionally, debris may be found inside the mid pipes and combusted from the extreme heat, resulting in a plastic or wooden burning smell.

Lowered Exhaust Pipe

Once the exhaust pipe is lower than usual, it is likely that the bolts are loosened or the flange is rusty and leaked.

Traveling with a lowered exhaust pipe can be dangerous because it can fall off at any time and cause accidents for other drivers.

Causes Of Flange Leak

Heat Cycles

There is a specific amount of water and vapor inside the engine bay.

The main cause of flange leaks is high temperature from 4-5 heat cycles, which constantly evaporates water from the inside of the exhaust system and releases vapor to the outside.

On chilly or rainy days, the evaporation rate is low, resulting in water stuck within the exhaust system.

The extreme heat boils the remaining water and stretches the wet exhaust flanges, leaving cracks on the surface of the pipes. Trash and debris can also get caught in these cracks and expand further.


Another reason for exhaust leaks is corrosion. After driving for two or three years, the iron forms a chemical reaction with carbon monoxide, water, and heat, resulting in iron oxide, or rust.

ust is the greatest enemy of the exhaust system.

Humid weather and muddy terrain may damage the corroded pipes even further. When the moisture in the pipes transforms into a liquid shape, the corrosion speed is even faster if the liquid cannot escape.

That is why you should clean the tips and pipes regularly to avoid any leakage.

How To Fix Exhaust Flange Leak

fixing an exhaust leak

How to fix an exhaust leak on flange? When a leak happens, you should address it as soon as possible. If you can’t take your car to a mechanic, here is a step-by-step guide to sealing exhaust leaks.

You will need a pair of gloves, glasses, sandpaper, acetone, exhaust tape, and toolkit to stop exhaust leak.

Shut Down The Engine

Turn off the engine when you hear constant strange noises or foul smells coming from the exhaust system.

If you are driving on the road, try to get to a safe place and let your car cool down for at least half an hour because the exhaust pipe is much hotter than the car’s engine.

Clean Leakage

Put on your rubber gloves and glasses to protect your eyes and hands. Use a piece of sandpaper to remove the leak on the pipes and apply some acetone to clean the damaged area.

Seal Exhaust

Depending on the hole size, you can apply exhaust tape, and it’s a quick fix exhaust leak. However, suppose the gap is too large; you will need to replace the exhaust flange in the garage.

Most exhaust flanges come with additional parts like the exhaust manifold, mufflers, and converter.

Some come with adhesive sealant to improve sound-suppressing capabilities and leak prevention. To install new flanges, you will need to remove old ones.

Inspect Pipe

Open up the car and identify the leak among the pipes. The front pipe is connected via the gasket on the exhaust manifold flange, while the rear pipe joins the exhaust pipe.

Remove Bolts & Screws

Use a ratchet or a wrench to unscrew all bolts and screws except for the ones on the sides of the header. If it’s difficult to see, use a flashlight to avoid them.

Separate Flange

Find a hanger to provide support for the exhaust pipe, so it won’t fall off while you are replacing the flange. Don’t forget to detach all connections in the manifold and the tubes.

Clean Flange Connector

Clear all residue on the surface with a piece of clean cloth. If there is rust, use a piece of sandpaper to scrub away and unclog the converter for better fuel efficiency.

Remove Old Flange

Should the old flange be stuck between the metal pipes, use a sharp metal piece or a knife to remove the blockage.

Remove the dirt from the interior. Apply sealant to both sides of the gasket before connecting the new flange to the system.

Install New Flange Gasket

After clearing the surface, carefully insert new flanges into the system so the sealant won’t overflow.

Use a ratchet or a wrench to reconnect the pipes, screws, bolts, and make sure to seal them tightly to avoid leaking.

Last but not least, start the engine to check for leakage. If you are still hearing sounds or feeling foul smells, it is likely that you haven’t sealed them properly.

Keep in mind that some gaskets require welding, so you should take your automobile to a professional mechanic for assistance in fixing an exhaust leak.


How Much Would It Cost To Replace The Gasket?

If you know how to seal exhaust leak, you would need some exhaust tape for about $20.

When you want to replace the gasket properly, you should take your car to a mechanic, which might cost you between $100 and $400, including the service charge and new flanges.

Cheap flanges cost about $2 – $5, while expensive ones are above $20.

Is It Safe To Drive With Exhaust Leaks?

No. Driving with an exhaust flange gasket leak is hazardous since the vapors include carbon monoxide and other toxic substances such as nitrogen oxides and phosphorus.

They can pollute your cabin faster than the surrounding environment.

How Long Do Exhaust Flanges Last?

A cheap exhaust flange may last 1 to 5 years, but more expensive ones could last up to 20 years, depending on driving habits and environmental conditions.

It is unnecessary to waste a lot of money on expensive exhaust gaskets since some may outlive your car’s expectancy.

Final Verdict

With this article, we hope you have learned how to fix exhaust flange leak conveniently.

Although it seems like a minor engine part, the exhaust flanges are crucial in keeping your car clear of harmful fumes and intoxication.

To avoid leakage, you should have your vehicle checked regularly to address issues on time.

Thank you for reading!

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