How to Replace the Hydraulics on a Farmall Model M
The Farmall Model M was manufactured in many incarnations from 1939 to 1952 -- all with a similar layout and four-cylinder engine. The tractor itself didn't come equipped with hydraulic cylinders. Most Model Ms came with "Lift-All" hydraulic power sources to run separate implements such as a loader. The loader would then have hydraulic cylinders that would link to the Farmall's pump. Some Model Ms had an optional two-way valve and still others had after-market valves driven by the engine, instead of the transmission. Replacing the hydraulics power take-off, or PTO, valves may be difficult due to corrosion, but it's not a complex task.
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Things You'll Need
- Replacement valve or valves
- Catch can
- Penetrating oil
- Propane torch
- Plumber's wrench
Instructions
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Purchase a new hydraulic valve based on the faulty unit. This will help you identify which valve your Model M had, and whether it was a stock or after-market unit.
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2
Drain the transmission fluid into a clean catch can by removing the drain bolt. Keep the catch can covered as you can reuse the oil, if it's not due to be changed.
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3
Apply counterclockwise pressure to the elbow-shaped hydraulic valve using a plumber's wrench. If the valve is bad, there is likely corrosion that may cause it to be very difficult to remove. If it is stuck, try a few techniques for removing stuck bolts.
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4
Spray liquid penetrating oil at the edges of the valve. Give it five minutes or so to work. Try the wrench again.
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5
Heat the valve with a torch if the penetrating oil didn't work. Using a low flame, focus the tip of the flame directly on the valve. Make sure there are no flammables on the adjacent surfaces and have a fire extinguisher at hand. Heat the valve for a minute or so, then give it at least 15 minutes to cool. The rapid heating and cooling cycle is very effective at breaking through corrosion. Try the wrench again. You may have to repeat the heat cycle many times with progressively more heat before the valve turns freely if it's extremely corroded.
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6
Inspect the threads to ensure they are still serviceable. If they are not, you will need to have some machine work done to repair them or use an automotive thread repair kit.
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Tape the new valve threads with plumber's tape.
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Thread the valve into the hole. Tighten it clockwise. You can use a smooth-jawed wrench if you don't want to mar the surface of the replacement valve. Or, you can wrap a shop rag around the valve before tightening it with a plumber's wrench.
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Repeat this procedure if there is a bad secondary valve.
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Replace the transmission oil.
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Tips & Warnings
Valves on vintage Farmall tractors are extremely tough. They are not impervious to corrosion, but most components can be rebuilt. If you must replace parts such as auxiliary hydraulic cylinders, it's generally a similar process of unbolting a threaded connection that's somewhat corroded. It's more likely you'll have to replace hydraulic hoses, which can dry and break over time.
Make certain the tractor is stationary and cannot fall out of gear or roll while you are working next to the engine near the large rear wheel.
References
- Photo Credit Jupiterimages/Photos.com/Getty Images
