Exhaust Leak/Carbon Monoxide?

[BCBrian]

Be careful, Jen.... CO is not something you want to breathe every day.

Have either of the cat's been replaced yet? That is A LOT of mileage for them if they are original. My Dakota blew the cat at about 80k..... sometimes they will plug up with particulates and sometimes they fall apart, mine got plugged.

Check out the manifold bolts, if you can get to them. Your mechanic may be able to use a sniffer to check for leaks. With that much mileage you could have a cracked manifold or just a loose connection as well.

[JeniorNV]

Originally Posted by BCBrian

Be careful, Jen.... CO is not something you want to breathe every day.

Have either of the cat's been replaced yet? That is A LOT of mileage for them if they are original. My Dakota blew the cat at about 80k..... sometimes they will plug up with particulates and sometimes they fall apart, mine got plugged.

Check out the manifold bolts, if you can get to them. Your mechanic may be able to use a sniffer to check for leaks. With that much mileage you could have a cracked manifold or just a loose connection as well.

Neither cat has been replaced. I haven't had ANY repairs done on this car at all (just battery, belt and spark plugs). Until recently, I thought the car was unbreakable.

I had trouble checking all of the manifold bolts. I wouldn't be able to check the underside of the exhaust manifold without removing the heat shield, and that particular shield would be a PITA to remove and put back on.

I'll report back on my carbon monoxide test tomorrow. My biggest concern is that I might have a small enough exhaust leak that the levels in the car are too low for the detector to read but high enough to make me sick in the long run. Or that I might have a small exhaust leak that could turn into a larger one. It's also very possible that there is nothing wrong with my car, except maybe a loose bolt that I haven't found or a rock stuck someplace that I haven't located. But I think the only way I will have peace of mind will be to get the car looked at. It's probably a good idea to do that anyway... It's only been to my mechanic twice in its life, and its last thorough inspection was at 30K miles.

[BRUTAL]

Close your "recirc" on the ac otherwise it pulls air from outside in front of the windshield and see if you co changes. Also manifold cracks can be very hard to find till they become bad. Reason being and also would illude to your high initial reading too. Is that cracks are open till the manifolds get warm/hot then they can seal tight and never be heard and defintly harder to see. Use a piece of hose to your ear when cold and put the other end by manifolds to listen. If it is a issue you dont have long to listen.
On my racecar the headers only bolt to the engine and each pipe slips into another to form the headers. When cold they leak and slip in and out easily. Fire it up and get some heat in the metal and they not only seal tight, youre not gonna budge them till cold again

[JeniorNV]

This morning's CO test was inconclusive. The CO detector didn't give a reading in the Mazda or the Frontier...but it didn't give a reading in the Vibe either. I think I'll need to repeat the test a couple more times to be able to draw any conclusions from it.

I found a paper written by the World Health Organization discussing CO levels inside vehicles (among other things). Here is the link. The CO levels mentioned were mostly from the 1990's, but vehicle emissions should be lower nowadays than when the paper was written. The average CO level in vehicles that are commuting in urban areas seems to be 5-15 ppm. Idling vehicles in Mexico City in 1994 were found to have levels as high as 43-59 ppm (their CO levels in outside air are through the roof). This makes my 80 ppm, although brief, seem rather alarming. But it is not surprising that the number dropped after the first 4 minutes of idling. Using numbers from the 1990's again, cold starting a vehicle is the equivalent of idling for 15 minutes in terms of CO production (although this figure might be different for a car built in '05 than one built in the early '90's).

I have an additional symptom to report from this morning. When I was sitting in the car with the heater running, I became aware of a whooshing/crackling/air moving kind of noise after idling for a couple of minutes. When I turned off the heater, the sound become very apparent. I popped the hood and got out of the car to investigate. The noise quit as soon as I got out, and I thought I was screwed. So I got back in the car and revved up the engine - voila, there it was again. I think I've actually heard this noise a time or two in the past, but it's sounded fainter and I'm nearly always running the heater. So I think it's been there for a little while, it just got louder today. I got a decent video... You can hear the noise when I rev up the engine and for a few seconds afterward. Turn the sound on your computer all the way up. Does this sound like it could be an exhaust leak? I guess it could be a vacuum leak too, but I think my other symptoms seem to point more toward exhaust. I can't find any loose hoses either. The noise sounds more crackly in person than in the vid.

Vibe Exhaust - YouTube

Vibe Exhaust - YouTube

This particular noise happens when the car is cold. The buzzing/rattling happens when the car is warm.

[JeniorNV]

I have an appointment with my mechanic next week to get the exhaust system looked at.

I decided to help rule out a vacuum leak by jiggling the vacuum hoses with the engine running to see whether the sound changed. I popped the hood, started the engine, and immediately went around to the front of the car and opened the hood. I noticed a strong exhaust odor in the engine bay that lingered for a bit. It reminded me of the odor that you get when you put gas in your car and the pump doesn't shut off and gas starts pouring down the side of your car. This wasn't a cold start either - the engine had been started and warmed up recently. I was able to reach all but one hose without getting too close to any moving parts. No change in the sound. The hose that I couldn't reach with the engine running passes a visual/jiggle inspection with the engine off. Doesn't seem to be a vacuum leak. The crackly air noise was present while I was doing this, and it seems to be coming from near the firewall of the car.

I went back to my control vehicle (the Frontier) and popped the hood, started the engine, walked around to the front and opened the hood in exactly the same way that I did with the Vibe. This was a cold start. There were NO exhaust smells whatsoever coming from the engine bay of the truck.

Time to quit ****ing around. I'm going to leave this one to the pros. Thanks for all your input, guys.

[BCBrian]

Just wondering if you got this fixed.....

[JeniorNV]

My mechanic has the car right now. He didn't get it finished by Friday afternoon, so I told him to keep it over the weekend. He started trying to track down the buzzing noise but couldn't figure out where it was coming from. He seems confident that he can find it; it's just a matter of how long it takes him. It sounds like he wants to fix the buzzing noise before he investigates the hissing noise (the one I posted)...partly because it's hard to hear the hissing over the buzzing, and partly because he's not sure whether the two sounds are coming from the same source. He doesn't seem to think the car has an exhaust leak, but I don't really think he's checked for it.

[JeniorNV]

This story has a frustrating conclusion.

In the first post, I had stated that messing with the heat shields made the loud buzzing noise get quieter, but that's actually not correct. Shortly after I posted that, the noise came back in full force and sounded exactly the same as when it originally started. Anyway...at first my mechanic was sure it was a problem in my exhaust system (he was thinking heat shields or catalytic converter). He removed all of the heat shields and did a thorough inspection of the exhaust system. The noise was still there and he couldn't find any other problems. So he spent a lot of time messing with various things on the car...moving and jiggling a bunch of things, hitting stuff with a rubber mallet, etc. while someone else held the RPM's at the right spot. He realized the sound wasn't coming from the exhaust or inside the engine bay anywhere... It was coming from in the firewall. He spent a total of 5 hours between Friday and today before he came to the conclusion that the noise had to be coming from inside the dash somewhere. He quit looking because it was "getting ridiculous" (his words), and the only way to figure out where the sound was coming from would be to tear apart the dash and go through it with a fine tooth comb. He thinks there is probably a loose bracket or something in the dash somewhere that's contacting another piece of metal in much the same way a loose heat shield would contact the exhaust. He said that he feels bad for not finding an answer because the sound is obnoxious, and he can imagine that it must drive me crazy when I'm going up a hill and hit the right RPM's (and he's right). I told him that he could quit looking.

I asked about the air escaping/hissing noise and the possibility of a small exhaust leak. He said it's possible, but the exhaust system looks fine and he doesn't see any other symptoms of a leak. He told me that if the car has an exhaust leak, it will get worse...so if and when that happens, I'll just take the car back to him. He said that if exhaust was getting inside the car (I told him that I had noticed exhaust fumes occasionally; I decided not to be up front about my CO detector tests), it might not necessarily be from an exhaust leak. The seals on the rear hatch might be compromised and allowing exhaust from the tailpipe to enter the car. I haven't been able to take the car through a car wash for a couple years because my doors leak water now...so that theory is certainly plausible.

As of right now, his opinion is that the car is safe to drive and mechanically sound. So that's the good news. The bad news is that I might have to live with the buzzing noise forever, which irritates the **** out of me. But I'm already being charged for 3 hours of labor, and it's really not worth it to have him rip into the dash if the car is safe and reliable in its current state.

P.S. For anyone who is curious, I repeated the CO detector tests several times on all 3 of my vehicles. I never got a reading in the truck. I got one reading in the Mazda while sitting in traffic in an industrial area, right behind an old Buick and with 3 semi trucks nearby. But I got multiple readings of CO in the Vibe, and the peak level was 340 ppm on an open road at the edge of town with no other cars around. So between that and the hissing noise, I'm not totally convinced that the car doesn't have a small exhaust leak. But it's safe enough to drive, so I'll just wait and see if it gets any worse. The positive readings on the CO detector have all been brief (1-2 minutes max).

[BCBrian]

I'd keep the detector in the car for now but since you already have leaking door seals, I bet the rear seal is toast as well.