Smell of natural gas from engine cmprtmt?

My 2000 GMC has started to have a very strong odor of natural gas coming from the front. If I drive with the windows open even a
little, it comes pouring in. Windows closed with or w/o the a/c on, absolutely nothing. Really weird, it is the *exact* same smell of home gas when you turn on the stove, you know, that odor they put in it so you know there's a gas leak? We even thought at first I had forgot to turn the gas off in the trailer we were pulling, but nope that was not it.
There is nothing leaking onto the ground anywhere and the truck runs fine, recently had it all checked out and fluids changed. Any idea what fluid in the car would smell exactly like this and why it would be so strong coming in when the side windows are open? Or what part might smell like that if it was burning or something?
thanks Frenchy
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Oxagen sensor ?? My GMC stunk like that . I got lucky ,brother unpluged it as a juke. He still hasn't figured out who took his valve stem cores five years later. I have a verry good memory. BTW I did that right after his wedding.
Jerry
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The odorant they put in natural gas is methyl mercaptan...there's nothing in a vehicle's systems containing this compound. When you eat asparagus, this is the stuff that makes your urine stink afterwards. A catalytic converter at operating temperature produces small quantities hydrogen sulfide which is a powerful odorant (rotten egg smell), detectable at a few ppm by people. It's usually released and from the coverter after low temp operation when it's adsorbed by internal cat washcoat and released on high temp operation of the cat. Unless the exhaust system is leaking past the converter and seeping from under the car to the front and sides this is usually only detectable from rear. Is it possible you are smelling exhaust gasses wafting back from the pipe?
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Augustus wrote:

More likely that the battery is overcharging and boiling off sulfuric acid fumes.
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On Wed, 12 Aug 2009 23:14:27 -0700 (PDT), frenchy

I guess that you have checked and sniffed all fluids from engine compartment, checked belt tensions. Checked that there is no bearing burning out from alternator, checked that auxiliary electric cooling fans are not jammed and burning hot..
That smell could come from car battery.
Check battery water levels if you dont't have maintenance free battery. fill if necessary. Check also that there is not overfilling in any of the cells. Check charging voltage at different engine revs. 14.2V max would be ok. Usually US made alternators charge little bit higher level than EU made automobiles. Check battery voltage with engine turned off. put some load for battery, lights on and check that battery level won't drop excessively. This is to check that there is no battery cells shorted. This all is to check that there is no battery over charging at any cells or whole battery that would boil the battery water and overspill battery water thorough overspill tube or blowing boiling gases out of the overspill tube or water filling caps. (Hydrogen, Oxygen) Clean battery and check that there is no cracks or leaks. Also check that battery is in its original shape, not ballooned or otherwise disformed. Grease battery connections with oxygen free grease or battery spray. Check also battery connections and that the battery is solidly installed.
If that smell doesn't come from battery, at least your battery is now overhauled.
--
Or that smell could come from raccoon that is half
rotten and stucked in your radiator (c:)>
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Thanks I'll check out the battery levels and the voltage, the voltage gauge seems to read ok, and will check the fan. This is definitely not wafting up from the rear, that's what we thought at first since we first noticed it with the trailer back there, but even with no trailer it is exactly the same amount of stink from the windows while driving. I'm almost positive it is not some other fluid in the car as I'm familiar with their smells. Also it is definitely not that rotten-egg smell associated with cat convertors, so pretty sure it's not an exhaust leak, just doesn't smell like an exhaust, fuel or cat conv. odor. The racoon joke is almost what I thought at first, I started hunting for some dead cat under the hood. I suppose their could be an animal hidden somewhere that I can't see it, this did happen first when we left a camping area, I'll look some more. Thanks everybody! Mark
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I just went out to the parking lot... battery looks fine, all cells are filled and identical, cell caps are on good, no bulging or leaks, terminals are nice and clean, dash gauge reads slightly above 14 volts. Belts are all new and look fine and correct tightness. Man I'm really starting to think maybe there may be a critter stuck somewhere under the truck after all, time to get out the work light tonight in the garage. That's the first thing I thought of when I smelled it! Mark
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frenchy wrote:

Could be a cooked critter over the cat. Not a fun thing to clean up. Wasn't anyone around the campsite who had some human scent masking product? A bit of the stuff I use to hide my scent from animals while heading to the tree stand could sure make a stink. (I know it can because some A%%WIPE poured about a tablespoon of skunk musk in the window wash jug on the truck a few years ago... The only way I got rid of that was to replace the tubing, jug and pump!!!!)
--
Steve W.

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Thanks for the laugh...
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How long has it been a problem? If a dead animal is the cause, it's not likely to cause a problem, or at least one of this magnitude, for more than one or two weeks.
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Been about two months, same now as when first noticed. I whiffed it again today on the way home and by golly, maybe it *could* be the smell of exhaust. Not a rotten egg odor but I'm thinking it definitely could just be an exhaust smell. I don't smell it at all when I pop the hood open, just driving. So perhaps it is somewhere aft of but close to the engine, where it could make it up to the side windows but not be in the engine compartment. I'm going to take it to the dealer and have them take a look, I don't want to get poisoned to death, if that's what it is. If it was the exhaust, how far forward would the leak have to be for it to come in strong thru the windows at speed? I'd think it has to be a pretty big leak for all the smell I'm getting, but I don't hear any odd noise like an exhaust hole.
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-Been about two months, same now as when first noticed. I whiffed it -again today on the way home and by golly, maybe it *could* be the -smell of exhaust. Not a rotten egg odor but I'm thinking it -definitely could just be an exhaust smell. I don't smell it at all -when I pop the hood open, just driving. So perhaps it is somewhere -aft of but close to the engine, where it could make it up to the side -windows but not be in the engine compartment. I'm going to take it to -the dealer and have them take a look, I don't want to get poisoned to -death, if that's what it is. -If it was the exhaust, how far forward would the leak have to be for -it to come in strong thru the windows at speed? I'd think it has to -be a pretty big leak for all the smell I'm getting, but I don't hear -any odd noise like an exhaust hole.
Do you have a camper window? There is usually a positive pressure on the back window. Other than that I'm not sure. Might be a good idea to let a muffler shop inspect the exhaust system.
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No, solid rear window. Muffler shop is a good idea, since now I'm 90% sure it is exhaust gas, thanks, will do. When my a/c system is set to 'fresh air', does it draw the air in from the vent at the bottom of the windshield, or from somewhere else? I definitely do not smell anything when using the vents and a/c blower. Till I get it figured out I have to drive it with the windows up and the ventilation fan on, or else it's stink-a-rama.
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As far as I know, all your vent air comes from the base of the windshield. But you have a rubber strip along the back of the hood, that does a good job of the keeping engine compartment air from reaching it. All engine air leaks would be outside that seal. Lift your hood and you can easily inspect it, and it's length compared to the windshield vent.
Do you have ANY aftermarket equipment installed? Something that might effect the ventilation of the engine compartment. Maybe an oil cooler or something?
I used to have a car that whistled at highway speeds. You never heard it, unless you drove under and underpass or something. I never figured out why.
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Just wondering if you ever resolved this smell of natural gas in your car, I have it in my honda CRV,
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replying to mckeon1960, Marci M wrote: I have it in my Mazda CX-9 as well and was wondering if this was ever resolved.
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I have this in my Mazda cx-9 as well! Did you figure out the reason for the smell??
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replying to ashleymvalentine1991, yehwhatevr wrote: No, I have not received any further comments about this... The majority of the comments refer to the oxygen sensor so I'm going to ask my mechanic.
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replying to mckeon1960, yehwhatevr wrote: No, I have not received any further comments about this... The majority of the comments refer to the oxygen sensor so I'm going to ask my mechanic.
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