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View Full Version : TECH: Exhaust Leaks


TROLL
12-16-2005, 11:43 PM
No one likes to admit it, but we've all had them at one point or another. Sometimes they go away on their own, sometimes not. Its embarassing, yes, but its something we should all learn about so we can do what we can to prevent this whenever possible...

EXHAUST LEAKS...

An exhaust leak is caused when the flanges of two exhaust pipes dont mate up properly to create an airtight seal when they are bolted together. A gasket is used in between these flanges to help them seal, but things dont always go as planned. Either from the start or over time, you might get an leak.
Exhaust leaks not only rob your engine of power, but can cause premature wear on components near the leak, and even leak dangerous carbon monoxide inside the cabin.

If you listen carefully, you can normally hear an exhaust leak. It will sound like a muffled exhaust note but the source of the sound will be the area that the leak is coming from. If you hear something like this you can put your hand near the questionable area while the car is running (without touching the hot exhaust) and you will be able to feel air if there is any escaping.
You can also know for sure that you are getting a leak if you take a look at your gasket when its off the car and it has carbon buildup in one section. This is the exact spot where the exhaust is not sealed properly.

In order to avoid exhaust leaks it is important to use high quality gaskets which will not only seal properly the first time, but they will not disintigrate too much over time and will continue to do their job for years to come.
It is also important to use a proper torquing sequence on exhaust bolts and also to torque them to spec. Not tightening the bolts enough can lead to a leak, but what a lot of people dont realize is that tightening them too much can also cause a leak. With this in mind, make sure to check the factory torque specs and follow them.

example of a gasket indicating an exhaust leak
http://www.bryantroll.com/other/gasket1.jpg

old and new gasket
http://www.bryantroll.com/other/gasket2.jpg

I just wrote this up quickly and of course it only has general information but if anyone else has any quality content to add to this please do... eventually posts like this will be reviewed and organized into a general technical reference with both basic and more advanced general car info.

Bryan

On Sale
12-17-2005, 12:01 AM
Another form of a Exhaust Leak can be caused by a "hole" or "crack" in the piping.

A hole in the exhaust can be caused by a few things. Rust can cause a leak, over time the heat and pressure can cause the rusted metal to break off, opening a hole in the exhaust. It can be the size of a nail head, to the size of a gold ball, heck i have even seen rusted exhaust's fall straight off a car, with no prior warning (as stated earlier by troll, exhaust leaks sound like a muffled exhaust.) Another way a hole can show up, is if your car is extremely low and you hit something in the road, punchuring the exhaust. As it isnt as common as the rusted hole, i have seen it happen many a times.

Another form of exhaust leaks, can come from where the exhaust is welded. If you, or the person who welds your exhaust, doesnt do a good welding job. The weld will eventually break down over time and crack, causeing exhaust to leak through it, this happened to me 3 times in my 240sx. The damn welds woudnt hold for some reason. So , if you hear a exhaust leak, check the welds, which is usually the #1 source for a exhaust leak on a welded exhaust.

I think this pretty much covers exhaust leaks, between me and troll, i dont think there is any of forms of exhaust leaks.

joe tom
12-17-2005, 12:33 AM
its funny that this topic came up, i had a small exhaust leak about 3 weeks ago, and had it welded. the only problem is that i don't know how long the weld will hold so i'm sorta in the market for a new cat-back system. i just don't know what i want. :(

TROLL
12-17-2005, 12:44 AM
what was leaking that you got welded? what catback and whats it made of?
bryan

the mike
12-17-2005, 01:15 AM
I have one now, jerk. I hope you are happy.


Seriously, I need one of those gaskets.

TROLL
12-17-2005, 01:19 AM
that gasket came off my car last week. one of three i replaced trying to find the strange noise. no luck...
bryan

99SL2_Modder
12-17-2005, 02:47 AM
I have a leak at a weld from my DP to my cat.

I may have one at my cat flange to cat-back, but I can't tell with the bigass leak in my dp. Wish I knew someone that could weld.

2point4DSM
12-17-2005, 12:00 PM
Bryan,
If you think your internal gate might be leaking you can always get another flapper installed. They don't go for much. DSM enlarged flappers go for like $12 and are easily installed.

On Sale
12-23-2005, 12:41 AM
I have a leak at a weld from my DP to my cat.

I may have one at my cat flange to cat-back, but I can't tell with the bigass leak in my dp. Wish I knew someone that could weld.

I can weld it for you. Depending on the time and work i put into it. I would charge you anywhere from $20-$50. but once again, it all depends on the damage that needs to be repaired. PM me for more info.

mostasteless
12-23-2005, 09:36 AM
that gasket came off my car last week. one of three i replaced trying to find the strange noise. no luck...
bryan

If you get someone to cover your exhaust tip with an old shirt it will make the leak louder and easier to pinpoint.

S4toSTI
12-23-2005, 09:40 AM
No you cover it with your hand... when its cold is better. EIther way i have one that comes and goes every so often when it is real cold out. I should probably check the gaskets at some point.

mostasteless
12-23-2005, 04:22 PM
This thread is jinxed, on my ride home from work I developed a rather loud exhaust leak. Turns out my egt sensor fell out :screwy: