How to Seal Exhaust Leak

Let’s face it: you don’t even think about the exhaust system unless there’s something wrong with it. That’s just how it is. Strange sounds, a funky smell, smoke coming out of the tailpipe – those are the things that instantly grab our attention. And what about a leak, you might ask? What are you supposed to do when there’s a leak in the exhaust?

Can this be sealed locally, with a basic set of tools? Or should you get ready for a steep auto shop check? I’ve got great news: even if the leak is pretty severe, there are some tried and true ways to fix the exhaust system. So, join me in this short, yet detailed guide, and let’s check out the most effective techniques for sealing an exhaust leak!

What does the Exhaust System Do?

The #1 job of the exhaust is to remove the gas fumes from the combustion chamber. It accumulates the vapors in the exhaust manifold and transforms the highly toxic fumes into something less harmful in the catalytic converter. Next, it dials down the engine noise in the resonator and the muffler and releases the gases through the tailpipe. Without a proper exhaust system, the fumes will escape into the cabin and the atmosphere unfiltered.

The Most Common Symptoms of an Exhaust Leak

The Most Common Symptoms of an Exhaust Leak

Before we move on to the “How to seal an exhaust leak” guide, it’s important to know about the common side effects of a leaking exhaust. Now, if there is, indeed, a leak, the first thing that you’ll probably notice is a strange noise coming from under the car (like puffing or ticking). Or, there’s gonna be a specific odor that resembles burnt fuel. The dashboard can also give signs that the exhaust is faulty, by the way.

The most obvious one is going to be a drop in fuel efficiency. This may not be very easy to notice right away, but if you know your car’s average mileage, you’ll definitely see the difference on the MPG display. The overall performance may take a hit as well; yet, it won’t be a dramatic decline, unless you’ve got a gigantic hole in the exhaust.

Adhesive Tape, Sealant, or Clamps?

Adhesive Tape, Sealant, or Clamps - Sealant

So, the more important question is – what are you going to use to seal a leak? You could, of course, use tape, but it should be an adhesive one. The most commonly-used brand is the 3M adhesive tape. What’s so special about it? First of all, it can withstand extreme temperatures (up to 300 degrees F, or more). Secondly, it lasts for a long time and is available for cheap.

Adhesive Tape, Sealant, or Clamps - Clamps

Right now, you can get it for 10-15 bucks, and it will be more than enough to fix the leak. Another frequently used remedy is the sealant (AKA exhaust putty). At its core, this is a filler product, an adhesive sealant, but specifically designed for “handling” leaks. It can seal out fumes at temperatures up to 2K (that’s two thousand) degrees. It’s commonly used on mufflers, converters, tailpipes, joints, and resonators.

The putty is available for $5-10, depending on the size of the package. Last, but not least, some experts recommend using clamps. However, in my experience, they’re a bit tricky, and you’ll need to get the exact right size for this to work. On the other hand, if you’re dealing with a large hole and not a tiny crack, a clamp will be the best solution.

Getting Right to Fixing

Getting Right to Fixing

Ok, that’s enough theory! We just figured out what the exhaust system does, talked about the most common symptoms, and made a list of the required tools/equipment. Now it’s time to get to work and figure out how to seal an exhaust manifold leak, or any other leak, for that matter. But wait: don’t forget to put on a pair of protective gloves! Say, the putty gets hard pretty fast, and that can hurt your hands unless you’ve got proper protection.

Eye goggles are also mandatory as all the debris that you’ll be scraping off can get into your eyes. That reminds me: make sure to get a wire brush or a grill brush to clean the pipes. That way, the tape or the sealant can “stick” to a smooth, even surface. Some sandpaper will come in handy as well. Don’t overdo it: you want the pipe surface near the leak to be nice and flat – nothing more, nothing less.

Sealing Regular Exhaust Leaks

The best thing about fixing a leak using tape or putty is how simple and straightforward the process is. All you’ll need to do is locate the leak, apply the tape or the exhaust putty product, and give it some time to “sink in”. For the putty, 30-60 minutes should be enough. For the tape, I recommend leaving the car’s engine idle for at least a day. Next, start the car and heat it for 5-10 minutes.

Don’t drive the vehicle; instead, keep your eye on the exhaust and make sure your fix is holding up. That’s pretty much all there is to know. Even if the crack in the exhaust pipes is rather big, it can still be fixed with a respectful amount of tape or sealant. Now, you will have to lift the car to get easy access to the exhaust, of course. For that, use a jack with a set of jack stands that will hold the vehicle up while you’re fixing the leak.

What about a Flange Leak?

What about a Flange Leak

Basically, an exhaust flange is a round device that is used to connect the different components of the exhaust system. Say, the muffler to the pipe, or the pipe to the converter, etc. So, as you can imagine, over time, a flange gets a bit rusty, grimy, and maybe even cracked by all the tiny rocks on the road. Sometimes, the flange loses its original grip, and that can also create a leak.

Alright, let’s learn how to seal an exhaust flange leak. Well, the concept is the same as with the regular leaks. But, you might have to remove the flange completely, seal up the leak, let it “breathe” for a couple of hours, and then put the flange back on. The 3M tape won’t be a very good solution for this problem. A gutty, in contrast, is exactly what we need. Apply it evenly, and make sure it covers both pipes.

Handling Exhaust Manifold Leaks

Technically, the manifold is an integral part of the exhaust system, even though it is located in the engine bay. So, go ahead and pop the hood. The factory manifold is usually one big tube (often kinda rusty), covered by a big shield. If it’s an aftermarket header, you’ll see multiple pipes instead. Visual inspection is the way to go here. Even the tiniest cracks, dents, or holes tend to cause a leak.

Some experts recommend starting the engine and looking for smoke. It might be coming out of a crack in the manifold, or any other part of the exhaust. Good news: the manifold is just another piece of metal, like the rest of the exhaust system. That means you can treat it using the same tools: tape/sealant. Give the car some time to rest before you start it up, and that should do the trick!

Conclusion

Summing up, I want to say once again that sealing an exhaust leak isn’t rocket science. If you’ve got the right sealant, know your way around the car, and can spend at least an hour on fixing this, you should be done with it in the blink of an eye. Today, we learned how to fix an exhaust leak on the flange, exhaust manifold, pipes, and also figured out how to seal the leaks using cheap, yet highly effective products.

Mechanics and auto shops charge quite a lot for identifying and fixing issues with the exhaust system. So, if you manage to pull it off on your own, that will save you a lot of money!

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