by Sally Colby
Because tractors provide power on nearly every farm, it’s important to know how to check them prior to use. Dr. Michael Pate, associate professor in the Department of Agricultural and Biological Engineering at Penn State University, says spending some time doing maintenance checks prior to heading to the field can save time and money.
Pate recommends checking PTOs and guards, both of which should be intact and in good condition. Checking the PTO includes looking for worn components, strings that may be wrapped around the PTO, the alignment of the PTO shaft with the drawbar and clearance. “There should be at least four inches between the PTO and drawbar so nothing binds,” said Pate.
The hydraulic assembly of the tractor is what allows it to be a true workhorse. The pressure in the hydraulic connection is extremely high, allows raising and lowering of implements, and sometimes provide rotational power. Pate suggests inspecting all portions of the hydraulic system for dirt and leaks. He noted that although dirt particles might be only a couple microns thick, the clearances in some hydraulic valves are between 0.0001 and 0.001 inches. “Any kind of dirt will cause wear,” he said. “It will bypass seals and cause the hydraulic system to leak internally.”
Pate added that an internal leak can cause a piston to lower slowly, which means hydraulic fluid has passed the seals due to wear or a broken seal. “If you lift a bucket up and notice that it travels slowly after the engine has been stopped, you probably have an internal leak,” he said. “External leaks are fairly easy to see — dirt and debris tend to cake up in the area of the leak.”
Check hydraulic hoses for wear. “There are multiple layers to a hydraulic hose,” said Pate. “Check for dry rot, breaks and cracks that could lead to failure. Make practical decisions but replace hoses when they start to wear. They’re under a lot of high pressure.”
Pate cautions farmers to avoid using their hands when checking for pressure leaks because the sudden burst of fluid from a worn hose can cause serious damage. “What you end up with is an injection of hydraulic fluid into your skin, which can cause gangrene,” he said. “There are very specific medical procedures to address it because the infection can become systemic very quickly.” Pate suggests wearing safety glasses and using a piece of cardboard while checking hydraulic lines. Any implements should be lowered to the ground to relieve the pressure in the system while checks are conducted.
The electrical system should be checked, including an examination of terminals for corrosion and wear. Pate suggests looking for clean connections, examining wiring supports, and checking for rubbing or binding as well as any pinch points that could cut wires. Make sure all lights are functional using the controls in the cab. Broken or burned out bulbs should be replaced immediately, especially for tractors that travel on the road.
Most tractors have some kind of ballasting system to add weight to the axle to gain traction and fuel efficiency. “If there’s proper traction when pulling, there isn’t a lot of wheel slip,” said Pate. “Wheel slip increases soil compaction and reduces fuel efficiency.”
Although wheel weights are usually necessary, they contribute to wear and tear on axles, hubs and the drive train system. Make sure there’s proper weight on the tractor based on what it’s being used for. Calcium chloride, hub weights or suitcase weights can be used to safely add weight to the tractor. Pate added that power hop can occur when tires are not properly weighted, and results in the tractor bouncing and bucking.
Although newer tractors have a wheel slip monitor, it’s possible to measure wheel slip with a tape measure and a calculator. “Know the circumference of the tires, and mark the tires,” said Pate. “Count the revolutions, drive a certain distance and multiply by the circumference of the tire and divide that by the distance traveled.”
When checking the transmission, look for overloading the transmission excessively through over-ballasting or working with too much of a load draft for the tractor size. Maintain fluid levels at the manufacturer’s recommended levels, and bear in mind that because the fluid is consumable, it’s going to wear out over time. “The additives in transmission fluid are polymers,” said Pate. “They stretch and pull back together, then start to break down, resulting in ‘cooked’ fluid.”
Always check oil levels prior to field work, and use the appropriate oil for the tractor. Each manufacture has an hour recommendation for oil replacement, but the operator should also consider type of use, dirt levels and conditions. “Wipe caps, wipe check sticks and make sure contaminants stay out,” said Pate. “Store oil where water can’t get in it.”
Pate describes SAE viscosity grades as a measure of how thick the oil is. “Multiple grade oil will act like a lower weight oil and flow easier at colder temperatures, then at higher temperatures it acts like a heavy weight oil,” he said. “So 5W-30 is a lower weight oil that flows easily in cold weather. 30W oil flows slower in hot weather — as you heat it up, it needs to be thicker so it doesn’t get squished out between the gears.”
Since brakes are used for both stopping and steering, checking and servicing brakes is a critical safety checkpoint. “Check for pedal free travel,” said Pate. “Pedal free travel is the movement of the pedal before it starts to engage. If there’s too little free travel, the brakes will ride on the drum. There should be enough free travel that the brakes engage quickly enough but doesn’t ride on the contact points.”
Tractor operators should look for loose fittings, leaks and check brake fluid reservoir. Check for uneven braking by placing the tractor properly on jack stands, then as the transmission is engaged, brake and see which wheels stop the fastest.
Tire pressure should be checked with a calibrated gauge, and inflation pressure should be set according to the tire manufacturer’s guidelines. “Don’t overload tires,” said Pate, “and don’t every exceed the tire speed rating. Use a safety cage (when inflating tires) because there’s a lot of force that can cause serious damage.”
Sidewalls should be examined for cuts, cracks or other damage. Tire tread should be checked for stubble damage, exposed cords and wear. Tires with less than 20 percent tread should be replaced. Examine valve stems for debris, cracks and corrosion, and make sure valve caps are clean and intact. Check nuts and bolts to ensure proper tightening. Check the ground contact area to be sure there’s no gap between the lugs and the ground.
While you’re behind the tractor, check to make sure there’s an SMV emblem that’s not overly faded, and properly mounted at the correct height.
Tractor work before the work
by Sally Colby