1940 Farmall A Split Part 2

While this post is going up in August, everything recounted below happened in July. I’m just really bad about posting it!

To recap: The Farmall developed a coolant leak in the clutch housing. The coolant would drip out slowly and drain the engine of water over a couple of days. This is most likely due to a failed expansion plug, which we are going to replace, and that requires splitting the tractor.

The next steps are to remove the various components that connect the engine block to the back of the tractor: generator, starter, wiring, fuel tank, and steering column (more on that later).

This tractor is very easy to work on, so I just methodically removed all of those things. From there, I removed the valve train cover and brought my engine hoist into place.

If I were to do this over again, I would have removed the front wheel assembly. My older engine hoist cannot hold the engine up for long periods of time, so I wound up just re-attaching it to the bell housing between work sessions. Without the front wheels, it would have been a lot easier to rig a stand or rest the engine block on the floor.

With everything supported, it’s straightforward to remove the six bolts that mate the engine to the bell housing. Once those are removed, if everything is aligned and level, the engine should just float forward.

Once I had it apart, I could very quickly see the problem. The water jacket expansion plug on the A is a 2 inch metal disc, and this one was heavily corroded.

I quickly removed that, and discovered a lot more sludge behind it. I used a long wire that I could bend into various shapes to clean as much of it out as I could.

Installing a new expansion plug requires removal of the flywheel. This was getting a little more complex, but I pulled the clutch pressure plate and clutch plate pretty easily! From there, there are some annoying metal covers to the flywheel bolts. They’re annoying because they are bent over the bolt heads to keep them from turning. They bend back (to allow removal) – but bending them back over the heads for re-installation was a bit frustrating. I probably should have put in new ones here.

I just realized I have no photos of the new plug! Trust me when I say I installed it. I wire-brushed the hole, and applied a bead of gasket material around the shoulder – the metal, having corroded over the years, couldn’t be trusted to provide a top-notch mechanical seal.

The expansion plug itself is slightly domed; you set the plug in the hole with the dome facing outward. Then you whack it with a hammer! This causes the plug to expand and fill the hole, if you’ve done it right. I recommend using a piece of wood or something that fits well over the plug in order to plant all the force in the most advantageous spot – the center.

From here on in, the re-assembly is mostly the reverse of the assembly. The flywheel is keyed, so installation on the engine is no problem. I gave everything a cleaning with some MEK – this project generated a lot of dirty rags.

I also took the time to sand and repaint part of the bell housing and peripheral equipment. The generate and starter got a nice coat of black, while the fuel tank got an internal cleaning and sealing to prevent any future rust.

I’ve mowed three times and have had great success with everything! One thing I would (and need to) do would be to clean the block more aggressively. Since re-assembly more sludge has made its way into the radiator, which really destroys the ability of the radiator to cool the engine. I’ll be flushing the system again soon…and someday I hope to have it completely sludge free. I marvel at how much garbage could be in an engine, and yet it still worked hard week after week. Truly the raw resilience of the old iron engines is incredible!