How to Quiet a Loud Exhaust

Vehicle exhaust systems do not just exist to deaden motor noise. They provide safety to the occupants by moving potentially deadly gases away from the driver’s compartment. So if your exhaust is loud or getting louder, you should fix it now–for more than one reason. We will tell you how to find the problem–then how to fix it.

And, of course, there are state Exhaust Noise Laws you probably do not want to have to deal with. Please go to SEMA Action Network>Resources for a list of local laws.

 

Common Causes of Loud Exhaust

Exhaust noise does not just come out of the tailpipes. Your exhaust system runs from the engine (exhaust manifold) to the tailpipes (usually sticking out under the rear bumper). In a Smart car, it is probably about 4′ long; in an F150, it is could be getting towards 20′ long. All vehicles have roughly the same components in the system regardless of length.

 

Inspect Your Exhaust the Exhaust System

Unless it is obvious where the noise is coming from, you should check out the complete system. Possibly you will find more than one problem. This is a listen, look, and feel process. (Make sure you do the ‘feel’ part when the vehicle is cold. Exhaust systems can be very hot. Driving 200 miles, then grabbing your exhaust pipe could leave you fingerprint-free for the rest of your life.)

• Manifold. With the vehicle running and the hood open (and the stereo off), listen near the top of the manifold. A rhythmic ticking sound may indicate a faulty gasket or cracked manifold. (It may also be a sign of engine knock or lifter noise. If you are not absolutely certain of the source, have a professional look at it.) When driving, you will also hear much more noise coming from the engine compartment because the exhaust system is not funneling all of the noise out of the tailpipe.
• Inline Gasket. If you hear a ticking sound, but it sounds further down the line, it will more likely be an inline gasket leak–usually the gasket at the connection of the manifold and exhaust pipe.
• Component Leaks. To check the rest of the system, you will have to get under the vehicle. Up on blocks or ramps, in park, emergency brake on, keys in your pocket. (I know–probably way too safety anal–but I came very close to having a vehicle fall on me due to hurry and stupid.) Look for obvious holes, cracks, excessive rust spots, black oily-looking spots. These will most likely be on the bottom of the pipe, with some starting to reach up the sides. (Motor and exhaust residue tends to run along the bottom.) Take a wire brush with you to clean off any likely looking spot so you can see and feel it better.
• Muffler. Mufflers quite often start rusting out or get holes in them. This usually shows up on the bottom near the rear, where residue and moisture collect. Occasionally your muffler will have a ‘pregnant’ look because it has expanded due to the outlet plugging up. In either case, it should be replaced.
• Catalytic Converter. These very rarely rust out but will begin to make excessive noise if the interior element breaks up and begins to rattle. If this happens, it will have to be replaced.

To double-check what you think you have found, tape your shop vac hose to your tailpipe (with the vehicle off), reverse it to blow, and pressure up the exhaust system. If there are holes, cracks, or gasket failures, you should be able to feel air escaping. You can also spray dish detergent on any suspect areas and watch for bubbles.

Note: If you do not feel comfortable doing your own inspection, some muffler shops offer a free visual inspection. 

 

6 Exhaust Noise Repairs

Once you know the cause of the noise, it is time to fix it.

 

1) Damaged Gaskets

Broken or damaged gaskets allow exhaust gasses and noise to escape from the system. Replacing gaskets will solve both those problems and increase vehicle performance.

 

Manifold Gasket

Replacing the manifold gasket is probably going to be the least fun you have this weekend. Make sure you have lots of Liquid Wrench penetrating oil and a socket set with a breaker bar. Manifolds have absorbed a lot of heat over the years, quite often making them difficult to remove–even if you don’t break bolts. You will find lots of YouTube Videos showing manifold gasket replacement–many of the vehicle or motor specific. You will also want your owner’s manual–paper or online–handy.

The gaskets themselves are not very expensive. The job is just labor-intensive and time-consuming, but if you are capable of doing it yourself, you will save quite a bit of money in shop costs. (Unless something major goes wrong like a broken bolt that requires an Easy Out to remove. Then it just takes more time.)

 

Inline Gaskets

There are probably at least 2 of these in your exhaust system–one where the pipe is attached to the manifold and one behind the catalytic converter. (For dual exhaust systems, there will be twice as many.) If you found one leaking noise and gases, replace it with a new Exhaust Pipe Flange Gasket. (Or you can use High Temperature Silicone Gasket Maker.) When taking the nuts and bolts out, make sure you have a can of Liquid Wrench handy because there is a good chance that the exhaust heat has made them almost impossible to remove. You may also want to get an Exhaust Manifold Hardware Kit (fancy name for 2 bolts and 2 nuts) and just replace them.

Note #1: I have used both gaskets and Silicone Gasket Maker. I like them both. The Silicone will probably do 2 or 3 joints, so it is less expensive. Just have to be a little more precise.

Note #2: If I had one gasket fail, I would probably replace them all. Everything is the same age and had the same use. Why take the chance of having to do it all over again in a few months?

 

2) Patch the Leaking Components

If you have found a hole or crack in the pipe, here are 3 options and their  uses. Follow the manufacturer’s directions to get the best result. They all take up to a few hours to harden, although some need heat to fully cure.

Note: None of these products work on rust. So make sure you use a wire brush to clean whatever part you are repairing. Shiny is best.

• Small Holes and Hairline Cracks. JB Weld High Heat Epoxy Putty
• Bigger Holes and Bigger Cracks. Yale Muffler Cement
• Any Hole or Crack (Within reason. If the hole is bigger than a quarter, there is a good chance your pipe is about to disintegrate.) Fiberfix Heat Wrap Tape

Full disclosure: I have never used any of these products, but from what I have read and the reviews, it appears they will do a very good job. As long as you do not ask them to do more than they are designed for.

 

3) Replace the Muffler

Muffler replacement is usually not complicated, but quite often, it can be hard work. If they are clamped onto the pipe, you are dealing with dirty, rusted, possibly immovable U-bolt clamps. If welded, you will be hacksawing a hard metal pipe while hunched up under the vehicle. Or you can use an angle grinder to cut both pipe and clamps. (Even if you can get the clamps off with Liquid Wrench and much swearing, you should just get new ones.)

Note: Angle grinders run at 11,000 rpm and cut like a damn. I use mine (the Makita I linked to) for cutting steel siding/roofing and stone veneer–among other things. It requires very little inattention to get into trouble while using one. If you have never used an angle grinder, this may not be the place to practice.

Once you have the old one off and have chosen your new quiet muffler (like the Walker Quiet Flow), you may need or want, all of, or some of, the following parts to get it all back together and working again. 

• Exhaust Hangars. You may not need new hangars, but unless the old ones are in great shape, I would replace them. (You have everything apart anyway, and they are just as old as the muffler.)
• Exhaust Pipe Adaptor. You can use these–if the exhaust pipe and muffler inlet are the same size–to eliminate welding.
• Exhaust Muffler Clamps. Needed to replace old clamps. Specially if you do not want to have to weld your components together.
• Exhaust Pipe Extension. May need to extend exhaust pipe to allow hangars to line up.

When installing the new muffler, follow your manual’s directions, re-assemble the system in the reverse order it was removed–make sure you read the instructions that came with the new muffler. (It is usually best to have the exhaust flow through the thing in the proper direction.) There are also plenty of YouTube videos about muffler replacement.

Note: Make sure you consult your owner’s manual (or go online) to find the type of replacement you need. Not only are there way too many choices, you have to deal with pipe diameter, muffler size, and compatibility. Also, hangar type and clamp type. Your manual should be able to give you the information you need to make informed choices.

 

4) Install an Exhaust Silencer

Install an exhaust silencer into the end of your tailpipe to reduce exhaust noise. These fit into the end of your tailpipe, reducing the size of the outlet (example: 4″ diameter to 2″ diameter) and reducing the noise somewhat. They are easy to install and inexpensive. Does not seem to be much information on exact decibel reduction. There does seem to be disagreement about the loss of performance because of extra backpressure. 

I fall in the camp of more back pressure is not good. So these would be among my last options to reduce the noise level. You might want to buy a decibel meter to measure noise before and after installation. This would give you some indication of how effective they are.

 

5) Soundproof the Floor

This option may appear to be selfish and uncaring about others. But if you have done everything you can to quiet the exhaust system and make it legal, it might be time to ensure that you can still hear your music. After all, no one is closer to the noise.

By using Noico 80 Butyl Sound Deadening Mat on the cabin floor, firewall, and trunk floor, you can eliminate or greatly reduce exhaust noise along with excess road noise and vibrations. The product is for interior use only. You will need a Noico roller to install it properly. One carton contains 36 square feet, which should be enough for your needs.

Warning: This stuff is addictive because of its effectiveness. You may find yourself putting it on the roof, trunk lid, and door panels to enhance your travel.

 

6) See a Professional

There is obviously a need for exhaust repair; otherwise, Midas Muffler would not have over 2000 outlets. If you cannot figure out what is causing the noise, or you do not enjoy lying under your car with dirt falling in your face, take it to a muffler shop. Having your exhaust system repaired professionally c/w parts and labor warranties can be a fairly attractive option. At least consider getting a quotation. Then you can compare costs of a professional to ‘Do-It-Yourself.’ And make an informed decision.

 

Other Things to Consider

 

Warranty

Usually, not much will go wrong with a new vehicle exhaust system in the first few years. But things happen. Just check out all of the various auto recalls. If you still have a warranty left on your vehicle, and you think that it is making more noise than it should, take it to the dealership and have it looked at. Can’t hurt, and they may find something needing repair–at no cost.

 

End Notes

I have maintained my own vehicles for years, and I am as much mechanic as I am a Covid expert. But I am convinced that most people can perform a great amount of their own vehicle maintenance. Usually, it is accomplished with about equal amounts of common sense, patience, time. And the owner’s manual and beer (after, not during).