Why Does My Riding Lawn Tractor Leak Oil?

The Source of the Leak

• As with any machine, there is no substitute for good maintenance practices in keeping a ride-on lawn tractor operational. On a clean, well-serviced tractor, the source of a leak can almost immediately be determined with the naked eye: Simply look above the ponding oil to see where it is coming from, be that the engine, the braking system or the transmission. If this is not possible, the machine must be cleaned before diagnosing the fault. If cleaning the machine inadvertently removes all trace of the leak, also, then check all fluids are fully topped up before running the engine again to create a trace, and operate it only as long as it takes to once again see leaked oil.

Engine Lubrication Oil

• Because ride-on lawn tractors generate a lot of atmospheric contamination -- dust, blown leaf particles and the like -- during their normal operation, oil leaking from the engine can be hard to spot. Make a habit of checking the oil level on your engine before every use; you will soon learn how much, if any, oil the engine burns in the regular course of its duties. If this varies, or if a leak becomes visible, simply trace it upward to discover the source. As the engine lubrication oil is effectively a sealed component, there are typically no hoses or pipes through which it is channeled, so the cause of the problem will very probably be a failed gasket.

Hydraulic Brake System

• Lawn tractors are almost universally equipped with a hydraulic braking system very similar in design to a car’s: They consist of a fluid reservoir with a filler cap, a pump, a system of high-pressure hoses, connectors at both ends of each hose and a braking mechanism on either two or all four wheels. Make checking the reservoir level part of your start-up procedure; under normal operation the level should never drop. A drop always indicates a leak. Visually inspect the system to discover the fault, then rectify it by replacing damaged parts before using the machine.

Hydrostatic Transmission

• According to the experts at Today’s Mower, hydrostatic transmission -- comparable to automatic transmission in a car, as opposed to the clutching and gear-shifting of more traditional tractors -- is the most popular form of transmission in use on lawn care equipment. As with the brakes described previously, the system operates with pressurized hydraulic oil. This oil can leak from joins and ruptures in pipes, and from damaged components. All hydrostatic transmissions consist of a reservoir, a pump and a system of hoses; all have seals that can potentially leak.

Oil Below the Air Filter

• In one circumstance, apparently leaking oil is not a problem. If, as a result of a mistake during an oil and filter change, there is too much lubrication oil in the crankcase, many ride-on lawn tractors have a vent tube -- properly called a crankcase breather -- that expels the excess oil into the air filter housing. This oil can then drip out of the housing and appear to be a leak, although it is not. In the case of engine oil dripping from the air filter housing, it is typically safe to continue operating the machine. Carefully monitor the level in the engine lubrication oil reservoir until the apparent leak stops.