bschen

I have always had a exhaust type of smell in my cockpit when I use the heat. I used the Nighthawk CO detector and it detected a low level of CO in the car. 60 ppm. I had all my air ducts checked and they were fine. No oil leaks on the engine. Should I be concerned?

horst

Well, the obvious: coming from the exhaust system. I would first check the integrity of the exhaust gaskets / seals, make sure a muffler has not been holed. You didn't say what year your car is, but a few (mine, for one- 90C4) came thru with part mild steel heat exchangers. I replaced mine. Yhey usually are SS. One of mine was SS, the other not. I have saved the one that I had that was perfect, (the left one) and it is yours free, for the cost of shipping. (they are a bit heavy). Is the CO only evident when you use the heater?

bschen

The car is a 1991 C4, the exhaust system was checked by a mechanic and no leak was noted. The air duct was realigned and clamps were replaced. No oil residue on the heat exchangers. The problem only occurs when the heater is on.

horst

If it only occurs when the heater is on, I would be suspicious of possibly a crack in one of the heat exchangers. Where these bolt to the heads, there is a steel sealing ring at each exhaust port, perhaps one of these have failed. Has any work been done which required the removal of the heat exchangers? Could be that they were not tightened properly, or mabey other problems. Mabey others have some ideas. The offer of a free exchanger is open, in case you need it. You will have to pay for shipping, however.

Dave R.

Benjamin,

Recommend you take this problem seriously and sort it out. At least, keep a good CO detector in the car and keep an eye on the trend. Note that OSHA has established the maximum permissible CO level for continuous
8-hour-per-day exposure in the workplace at 35 parts per million. Are you going to pass out & die? No, probably not. However CO is not a Good Thing.

This issue comes up in the light aircraft world, and it kills pilots on a regular (if relatively infrequent) basis. Air-cooled piston engine aircraft provide cabin heat in the same way as our 911s, by flowing air over the exhaust system and then into the cabin, so leaks in the exhaust allow carbon monoxide into the cabin with the warm air. Worst case, pilot loses mental sharpness to a dangerous degree and even consciousness.

I would not fly in an airplane exhibiting the same levels of CO as your car. Of course, risks in the plane are greater, since coasting to a semi-conscious or fuzzy but safe stop by the side of the road is a lot harder to accomplish in an airplane than a car, and higher altitudes can increase the CO's effect.

Here is a link to an article on carbon monoxide and detectors in a light aircraft context, it is long but clearly written & has lots of good information. <a href="http://www.avweb.com/articles/codetect/" target="_blank">http://www.avweb.com/articles/codetect/</a>

Good luck

bschen

I actually did a more detailed test. The CO detector registers on initial cold start. It goes to about 60-70 ppm. I rolled the windows down for a few minutes and it goes to 0 ppm. When I am driving the car, and even at park, the detector reads 0 ppm. When I turn the car off and restart it (warm engine), the detector reads a lower level, about 10 ppm. It seams that, the CO only gets into the car on starting the engine. Especially on cold start. Could this be normal?

mikeporsche1990

I notice the smell of exhaust with the heater on when the engine is cold but it goes away once the engine warms up (either that or I am in delerium since you cna not smell CO). I would be interested in the answer to your question.

Bill Wagner

Benjamin:

Where did you get the CO detector and how much did it cost?

<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Dave R.

Benjamin,

sounds like things are OK.
When the motor is cold it is set up to run rich, which generates much CO, and also the cat is cold and is not scrubbing the CO. Probably the engine fan is sucking in a little of the exhaust as you idle in place (and also the heater blower motor which taps air from the fan shroud), so you catch a little of the smell. I notice that too at cold startup. If you are not seeing any CO readings with the heater full on and the car in motion, I would not worry further.

Bill, for information on different CO detectors and where to find them, hit the link I posted earlier in this thread.