smoke out of the left tail pipe.

[Lance-ftw]

Just noticed this morning that my truck is spewing some smoke out of the left tail pipe only. It isn't particularly thick and it's white in color so I'm not sure if it's steam or what but it's only the left pipe which confuses me.

I noticed while it was warm that the left pipe was spitting a little bit of white which maybe was steam and now that it's cold outside maybe it's just more obvious since it's not dispersing as quickly in the cold air.

What sort of things could be causing this? I need to put antifreeze in the truck once every couple of weeks but I'm pretty sure that's because it's blowing out on the road from the little hose on the radiator cap (I don't have a resevoir or a closed system installed yet) and we pressure tested the system and it held pressure fine.

Any ideas?