At 100K I installed Rusty's catback. Now at 145K I installed a much overdue catalytic convertor in front of the catback. While everything appears to be bolted up tight and solid, it now sounds like I may have a minor exhaust leak. Is there any way to definitively detect exhaust leaks easily? TIA
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Exhaust Leak
- Thread starter yardape
- Start date
outlander
NAXJA Forum User
- Location
- Columbus,Ohio
Isn't there a special die or chemical that you put in the gas that enables you to use some kind of special light to detect exhaust leaks?....maybe someone with a little more experience on this can chime in.
Maybe I'm dreaming.
Maybe I'm dreaming.
5-90
NAXJA Forum User
- Location
- Hammerspace
I usually just listen to the thing - may take a little crawling.
Check around the manifold mounting surface, and down at the collector flange and the catalytoc converter flange (if you retained the bolt flange) as the obvious starting places.
There may be some sort of UV Dye you can put in the fuel, but why would you really want to bother? It's a lot of work for a short trip.
I know about the UV dyes used in oil, coolant, and Aircon - but that makes a little more sense. Those leaks are usually pretty quiet (but the neon green antifreeze is usually easy to spot...)
5-90
Check around the manifold mounting surface, and down at the collector flange and the catalytoc converter flange (if you retained the bolt flange) as the obvious starting places.
There may be some sort of UV Dye you can put in the fuel, but why would you really want to bother? It's a lot of work for a short trip.
I know about the UV dyes used in oil, coolant, and Aircon - but that makes a little more sense. Those leaks are usually pretty quiet (but the neon green antifreeze is usually easy to spot...)
5-90
My exhaust started making a sputtering sound sort of like the sound of passing gas after installing a much overdue catalytic convertor at 145K. With that kind of mileage one might assume that a cracked manifold would be a starting point but I don't have any experience with spotting that or where on the manifold it would be. I assume it would be a hairline crack. Is welding it a permanent fix? Might the leak prevent the Jeep from passing a dynomometer (emissions) test which was the reason for the cat replacement? TIA
5-90
NAXJA Forum User
- Location
- Hammerspace
While a hairline crack is a possibility (and it would be down by the collector,) it's the sort of thing that usually shows up at 180-200K or thereabouts.
I'd have to hear it, but it would depend largely upon the frequency of the sound at idle. If it was regular, with no pauses, I'd start looking down at the collector and work backwards.
If there were distinct "pauses" between "putts," I'd check around the mounting surfaces between the manifold and the head.
It's a known issue that the manifold bolts tend to work loose, simply because they have to hold aluminum and iron - at the same time - while they're heated. Even though the aluminum doesn't get anywhere near as hot at the iron exhaust flange, aluminum also expands twice as fast as iron (1.2e-6 inches/inch/degree F vice 6e-7 inches/inch/degree F) and that will generate a "twisting" load on the bolt - which eventually starts to unscrew it. That's why I retorque once a year - eliminates one more check when something gets silly.
As far as an exhaust leak failing smog? I've gone in with exhaust leaks before and had no trouble. For the dyno test, I have a simple solution - I've told them I've converted my XJ's to All Wheel Drive, and they therefore can't be dyno'ed. There are two people who are authorised to drive my vehicles, and we're both here as I write this. Anyone else will just have to wait until one of us gets there...
5-90
I'd have to hear it, but it would depend largely upon the frequency of the sound at idle. If it was regular, with no pauses, I'd start looking down at the collector and work backwards.
If there were distinct "pauses" between "putts," I'd check around the mounting surfaces between the manifold and the head.
It's a known issue that the manifold bolts tend to work loose, simply because they have to hold aluminum and iron - at the same time - while they're heated. Even though the aluminum doesn't get anywhere near as hot at the iron exhaust flange, aluminum also expands twice as fast as iron (1.2e-6 inches/inch/degree F vice 6e-7 inches/inch/degree F) and that will generate a "twisting" load on the bolt - which eventually starts to unscrew it. That's why I retorque once a year - eliminates one more check when something gets silly.
As far as an exhaust leak failing smog? I've gone in with exhaust leaks before and had no trouble. For the dyno test, I have a simple solution - I've told them I've converted my XJ's to All Wheel Drive, and they therefore can't be dyno'ed. There are two people who are authorised to drive my vehicles, and we're both here as I write this. Anyone else will just have to wait until one of us gets there...
5-90