Farmall M Carb/Manifold Condensation?

Tue May 10, 2005 9:45 pm

The M runs, just for a short time and kind of rough but it runs. While it is running I noticed moisture/condensation on the top of the carburator where it is attached to the manifold. Anybody with an informed diagnosis out there. Thanks.

Wed May 11, 2005 6:10 am

The vaporizing gas causes the temperature of the manifold to drop so that moisture in the air condenses. It will turn to ice in the winter.

Wed May 11, 2005 9:03 am


That's completely normal. Just like the condensation on your cold adult (iced tea?) beverage it's caused by the cold surface in humid air.

Wed May 11, 2005 5:06 pm

I've been having carb ice somewhat lately myself on the H. I don't think vaporizing fuel is the problem. Excellerating air through the venturi causes a drop in pressure and thus a drop in temperature. In A&P school they taught us that it is roughly 30degrees. Therefore the problem will be at its worst at about 60degrees. Colder air is not as big a problem because colder air contains less moisture. This spring time air has been ripe for the condition. Frost will form on the throttle plate and can accumulate to the point that and engine won't idle but may not be noticed above idle. What I do when mine forms carb ice is to just shut it off for a couple of minutes and let it melt. Second time I fire it up it usually is OK after that. This was a topic I brought up a few night ago on the chat forum.

Wed May 11, 2005 7:24 pm

Colder air holds less water, but the warm air that entered the system is holding plenty more. That moisture is condensing out as it cools inside the manifold so you are getting that water anyway. When it's icing on the outside, it's icing (or snowing) on the inside as well.