Exhaust Smell when driving

[Flying_NEB]

Hey, I got one for ya. I think this might be an exhaust leak somewhere, but you tell me. After the car has warmed up a bit (10 minutes or so) I begin to smell a hint of exhaust. I've never had this in either of the other neons I had. It's especially noticable when I'm stopped. Could this be an exhaust leake somewhere? How would I figure it out? Where is it likely coming from?

[Canada]

Start you car, take a rag and plug the exhaust pipe and listen for leaks.

If, when you left off the end after holding it for a bit, you get a large whoosh of exhaust, you probably don't have a leak...

[Frizbe]

I believe a more scientific way to test for leaks is to get a spray bottle and put some soapy water in it and spray the exhaust, then if/when it bubbles, you found your leak.

Of course this means you can only test the bottom of the exhaust, but still.

[OB]

Since you smell the exhaust, the leak is probably before the cat. Neons have very low tailpipe emissions, so a leak after the cat would be irrelevant (unless the cat is bad, of course). A leak before the cat would likely cause the car to run a bit strange, since ambient 02 is being sucked in between the exhaust valves and the cat. The 02 sensors will read unusually high 02, and will richen up the mixture to compensate. Many of the components ive referred to could also be operating poorly/broken, resulting in similar results. For example, a bad cat might allow unburnt fuel out of the tailpipe. A bad 02 could cause the car to stay in open loop longer/permanently, causing poor emissions and poor operation, along with unburnt fuel exiting the tailpipe. Simple thing to do would be to check for leaks, then check the sensors and if all else fails check/replace the cat. It could be a number of things.

[halford637]

I'm not sure what year your car is but I had that problem on my 2000 a about a year ago...There was a hole in the exhaust manifold under the heat shield where it had just rusted through. I just had it spot welded for a temporary fix, but I could smell the exhaust in the car when I wasn't moving, 'cause the fumes would come out of the engine bay right into the blower ducts. On a side note it is doing it again now but it's okay because I'm taking the whole motor out in 3 weeks anyway.

[Flying_NEB]

yeah, mine's a 2000 also. I was kind of hoping for a reason to get a header =) I'm going to be doing some work on it on Friday and I'll let you know what I find out.

[Flying_NEB]

Alright, now that it's been a year I guess it's time for me to check this out. Can someone explain a little better how to check for leaks?

I read up above about using soapy water - do I just spray that on the manifold? I'm assuming I have to take the heat shield off right?

Thanks for the input.

[jake_tim]

....if you sprayed soapy water on the exhaust manifold it would just violently fizzle and evaporate I would come up with another idea bud.

...I don't have any though, sorry.

-Jacob

[Flying_NEB]

thanks for heads up. I kind of thought it was odd that something sprayed on the outside would bubble.

[denlevi]

The idea of spraying a soapy water solution would work for a very short window of time when the engine is still cold. You would have to remove the exhuast shield then start it and quickly spray it down and check for leaks, unless when you remove your exhaust shield you find its obviously a gaping rust hole in your manifold.
My guess would be if you have a leak in that area its going to be at the union of the exhaust pipe and manifold, and usually you can hear the leak as a popping noise coming from the exhaust.

[occasional demons]

If you are removing the heat shield you would prolly see the crack anyways. If you wanted to attempt the bubble method, remove a spark plug get a 1/4 pipe nipple about 6" long with a air coupler on one end, or a compression tester with the check valve unscrewed from the end, and thread it into the hole. put some air pressure on the pipe/compressoin tester hose and check for air out the tail pipe. remove the air and turn the engine some and reconnect till you hear the air if you don't the first time. Or you could remove the VC to visually see the exhaust valves open for that cyl. if you wanted to go to that length. Didn't think so. Once you hear air from the tail pipe stuff a rag or something in it to create pressure, or have a helper put their hand over it. then spray away with no worries of the soap, (or yourself) getting burned) off.
Note: just stay clear of moving engine parts when applying air pressure to the cyl. as the air will drive the piston to the bottom if both inake and exhaust valves are closed.
If you don't have access to a decent air compressor, then obviously you can't do it this way. It would need to be at least a 5 hp or better. Those little 12 volt cigarette lighter ones ain't gonna cut it for this. You need some volume (air flow), not pressure. But if it's available it would be safer than attempting it while the engine is running.
edit: if you can't hear the air at the tailpipe. hold a candle or match (or something that smokes) near the end and check for air flow that way. Don't do this if you have a fuel leak, tho.

[Flying_NEB]

Thanks. I'm gonna remove the heat sheild and look at it...once it's nicer weather. I'll let everyone know what I find.

[Flying_NEB]

Well, I got the heat shield off and I don't see anything obvious. There's lots of caked rust that is peeling and chipping off and so it looks like a crack, but I think it's just the rust chipping off.