Oil Leak on a Self-Propelled Toro Lawn Mower

Overfilled Crankcase

• Toro’s self-propelled mower Kohler engines , namely the XT-7 series models, have oil capacity limits in their crankcases. The average capacity is between 20 and 22 ounces, depending on the model. If too much oil is put into the crankcase, excess oil will spill into the combustion chamber. Any excess oil will move into the exhaust system and leak from there into the muffler or ignite into smoke. Leakage can also happen if the mower is tipped over in the wrong direction, forcing oil out of the crankcase and into the combustion chamber or air filter.

Piston Rings

• The XT-7 engine’s pistons build up air pressure and heat from operation and combustion. The mower’s oil system cycles around the pistons to transfer heat and remove dirt and grit. The pistons have rings that keep oil from leaking inside the cylinder during operation. If these rings break or wear out over time, oil can leak into the cylinder and combustion chamber. If the oil fails to ignite in the cylinder, it will move to the exhaust and burn up there.

Breather and Exhaust

• When the oil cycles through the XT-7 engine, it passes from the combustion chamber through breather tubes and filters. The breather tube relieves air pressure while the filters remove dirt and debris from the oil. If the tube or filter becomes clogged, the oil will not pass through and builds up around the pistons and combustion chamber. This build up can cause leaks throughout the engine’s seals and gaskets.

Leak Prevention

• Sticking to the XT-7’s maintenance plan can help prevent oil leaks. Check oil levels prior to every start to ensure oil isn’t above capacity. Change the oil after 50 hours of operation or every year so that there is no contaminant buildup that can clog breathers and filters. Inspect filters every 25 hours and clean or replace as necessary. Also keep all ventilation and fill areas clean and free of debris to reduce chances of entering the engine.