High CO levels on the ground in a PA28-180

[flyzone]

I have a 72 Cherokee 180 with a portable CO meter and during ground ops I regularly get pretty high readings of 50 or more. In the air the readings are zero or maybe 1. The airplane has a new exhaust system and my A&P says there are no leaks. I guess the leaks are coming in from less obvious places, but where? It would be nice to know the most logical entry points of the CO into the cabin. If I open the small vent window the reading drop like a rock. I would think the prop would blast this stuff away but I guess not. I lean the mixture way down on the ground but this doesn't seem to help much.

Has anyone done any testing for this or know of ways to reduce these cabin leaks in Cherokees when the plane is on the ground?

 

[Sinistar]

Maybe just another data point. With everything buttoned up in the winter and idling for a bit first to warm it up, I have seen the CO monitor read as high as 32 during run up. That is well within short term limits. During the summer it is always really, really low (0..2). In the winter in cruise we see about the same. Its like the less than perfect door seals along with all that prop wash blasting by the doors at high speed creates a slight vacuum inside the plane and the exhaust is then drawn in since the plane isn't moving through the air. Just my theory anyway.

 

[Radar Contact]

It is normal to see a high CO while on the ground. The prop/wind can easily swirl the exhaust into the cabin. As long as you see a 0 reading in the air (especially while using the heater) then you have nothing to worry about.

My $0.02

 

[MooneyDriver78]

Try leaning it, leaning it will reduce CO emissions.

 

[flyzone]

I lean it aggressively on the ground but it doesn't seem to lower the CO to an acceptable range. The low cabin pressure comment is interesting. When I open the vent window perhaps the pressure must get equalized and the CO level drops significantly though still not low enough. I thought it just might be fresh air but perhaps it's more than that.

Even though the readings are zero or 1 in the air I always had a nagging feeling about safety.

Thanks for the feedback.

 

[flyingron]

The Navion can get high CO in the cockpit while sitting stationary on the ground with the canopy open with no wind. It's all a matter of where your pipes are with regard to the cabin airflow. Getting a little forward movement typically gets rid of that.