Ask the Mechanic

Misted Engine

(Steve Thompson)

Water in the wrong place in an engine usually means trouble. The accompanying photo of the rocker arm assembly on this 850 Ford tractor reflects a couple of stuck valves. The engine was rebuilt two years ago, and recently, after not running for a long period of time, it lost compression on two cylinders. What caused this was a stuck valve on both dead cylinders.

I noticed the oil bath air cleaner was leaking out the top of the cup. When I removed the cup, it was running over with mostly water. What I believe happened is that as the water, rather than the oil, rose up from the vacuum in the screen above it, the engine was forced to breathe through the water-soaked screen.

Normally, after the engine is shut down and no more vacuum is holding the oil in place (with oil in the cup), it drips down in the cup along with the particles, which sink to the bottom of the cup. Instead, this water solution was slightly misting the engine as it was running. The carburetor had problems because of water, too.

When the tractor was not run for a while, the valve stems became stuck to the valve guides. I tapped on them after soaking with Marvel Mystery Oil and Sea Foam. Both of these products have been around forever and are great additives, especially for engines that are not used frequently or only for short periods. Little by little, the valves started closing slowly and finally became free.

An exposed oil bath air cleaner, like on this model Ford tractor, if left outside can easily take on water around the clamp that secures the cup to the body of the air cleaner.


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