Exhaust leaks are obnoxious and can be a real pain in the butt if you don’t know how to find them and repair them quickly.
Exhaust leaks can be bad for your car but also bad for your health.
Read this article to see how driving with an exhaust leak can turn bad real quick.
Not sure what an exhaust leaks sound like? Watch this:
Or this clip of a Dodge Ram Hemi with a loud exhaust leak:
Exhaust leaks sound like a car is farting in a sense as it goes down the road. It makes them louder in a way that doesn’t sound good (like a well tuned exhaust). Usually you can hear it coming from under the engine bay or the middle of the car, whereas with an exhaust system you typically hear it further back.
A tuned mechanic’s ear can hear an exhaust leak coming from a mile away.
I always point them out to friends, and then quiz them the next time we hear another car with an exhaust leak.
Goes like this (Me) “What’s wrong with that car?” (Them, annoyed) “An exhaust leak! Stop asking me!”
People spend way too much money paying a shop to diagnose the exhaust leak and install new parts.
When really the parts could be repaired by you, without spending any money on new pipes, exhaust, or mufflers. You simply need to find the leak first, then figure out what method will be best to repair it.
This guide is assuming you do not know how to weld, and do not want to learn how to weld to repair the exhaust leak.
First. Lets see if you have an exhaust leak and where it is:
There are a couple of easy tips and tricks to help you find exhaust leaks.
1. We Need To Create Back pressure in the Exhaust System:
We want to make the exhaust leak worse temporarily so we can find it easier. This can be done by making it harder for the gases to flow out the exhaust (by clogging it) or by putting a leaf blower / vacuum in the exhaust and blowing it the opposite direction (while car is off).
Easiest Starter Method:
The method I personally like that is the easiest to do quickly only take a rag or something to clog the exhaust with.
Start the car and let it run with the rag stuffed in the exhaust. It doesn’t need to be perfectly air tight. Here is Eric The Car Guy showing how to do it (video is cue’d up to exactly when he stuffs the rag– I know no one likes watching a 5 minute video for the 10 second part they need).
This will create a backpressure in the exhaust and the leak will become much much louder and easier to find.
Once you find the general area that the leak is in, go fill a spray bottle with dish soap and water.
Spray around the leaky area (on as cool of an engine as possible) and see where the bubbles are formed. This is where you have an exhaust leak.
The Best Method / Safest:
Grab a shop vac or leaf blower and put in the exhaust.
Reverse the hose on the shop vac so it is blowing air out (like a leaf blower). Put it in the exhaust (use tape to hold it in airtight).
Then turn it on and this will create a backpressure system inside the exhaust.
This allows you to work on the car while it is cold, and spray as much dish soap water around to find the leak.
This method means you won’t have to worry about burning yourself, and can take your time under the car without breathing in a ton of exhaust fluid and burning yourself on the hot exhaust.
Here is ChrisFix using this method to find exhaust leaks on a mustang (video cue’d up perfectly):
Listen for hissing noises then spray the water and check for bubbles.
Be thorough. Quite often there is more than one leak in an exhaust system.
The most important places to check are near welds, flanges, and anywhere pieces are bolted onto the engine (headers etc.)
Anywhere where there is a gasket is a common spot for a leak, and two metal surfaces being mated together.
Look for rusty spots and focus on those. The dish soap solution and a spray bottle will be your best friend here.
Second: Now That You Have Found An Exhaust Leak How To Repair It?
This depends on where exactly is the leak. This will change your approach for fixing it. There are a couple things on the market to fix exhaust leaks and they each work well if they’re used for the correct purpose / application. (All links go to Amazon)
Before using any of these methods it is important to understand some basic concepts that apply to all car repair.
The surfaces where any sealant, adhesive, or tape will be used must be extremely clean.
For exhaust surfaces this means cleaning the rust and junk off with sandpaper and rubbing alcohol.
You want the surface to be really really clean, otherwise no product will work correctly and you will be disappointed.
That is why a lot of these products don’t have good reviews. People do not understand how to apply them, and specifically how to prepare surfaces for them.
You will need sandpaper and rubbing alcohol to clean the spots where you will be applying any of these substances. You should also have a wire brush as well to help with scraping the initial rust off.
If you skip this step or do it poorly I promise you will be disappointed in the fix. Even if you were going to weld it, the first thing a welder would do is make sure to clean it up properly.
Here is ChrisFix showing us how to apply each of these products and showing us how to clean it up correctly.
The Best Way To Repair Exhaust Leaks Is To Weld Them
Hands down. If you can afford it or do it yourself then weld the exhaust leaks.
If you want to save money on the exhaust leaks then find the leak first and call a local welder and ask if they will do it.
It will save you money if you already found the exhaust leak and all they have to do is weld it.
Or if it is a part you can easily take off the car, just remove it, clean it up for them and take it to them. They will happily weld something fast for you where they don’t need to get under the car or do any diagnosing.
That means too you don’t have to go to a strictly automotive type welding shop, you can go to anyone that can weld anything!
However, if you want to give those products a try I listed above if you do it right they should last you awhile. If you don’t follow the instructions or don’t clean anything before applying, they are useless!
Hopefully that helps you feel more confident in how to find an exhaust leak, diagnose it, and your options for repairing it.
Couple last things to remember about working on exhaust stuff:
Also remember that there are gaskets that sometimes degrade, and it may just be as simple as replacing the exhaust gasket. They usually are pretty cheap, but whenever you’re working on exhaust stuff you are definitely bound to run into rusty and bad bolts.
Best to use penetrating oil first on exhaust bolts, and I wrote a how to article where you can make your own penetrating oil for cheap (that works better than all the name brands out there).
Products I mentioned in the article / are good to have for diagnosing exhaust leaks (check links to see if you already have them at home):
For The Repair Part (You Probably Have A Lot Of These):
- Exhaust Putty
- Tape For Exhaust
- Exhaust Clamp
- Wire Brush Set
- Isopropyl Alcohol
- Good Shop Rags
- Nitrile Gloves
To Diagnose Exhaust Leaks (You Probably Have Something That Will Work):
- Cheap Electric Leaf Blower
- Or a sweet shop vac that also has a detachable leaf blower (click here)
- Good Shop Rags (or an old t-shirt to clog the exhaust)
If you want to see how to make your own penetrating oil, read my article here.