I Have an Oil Leak in My Lawn Mower

A Clean Machine

• Accumulated grime can cover a leak source and overheat the engine. Heat that is normally dispelled through the engine case can be trapped by the buildup. Overheated engine parts can expand and contribute to leakage. Use rags to clean large engine surfaces, and plastic cutlery, like spoons or knives, to dig grime out of tight spaces without damaging paint or engine components. Any screw or bolt heads uncovered may be instrumental in leak detection or repair.

Nuts and Bolts

• Check all engine bolts and screws for tightness, using light force. Oil seepage uncovered by cleaning may help provide a focal point. Any fastener that turns easily may be the cause of the leak, but consult the mower manufacturer's torque specifications before applying much pressure on a fastener. Certain bolts may snap off if overtightened, while others may need to be tightened in sequence with associated fasteners. Still other bolts, such as engine mounting bolts, thread into nuts under the deck.

Maintenance Issues

• Improper oil or oil levels can generate leaks, and so can clogged filters or breathers. Service any maintenance items that require attention, and start the mower. Observe the mower while keeping hands and feet clear of the blades at all times. Once a leak is spotted, shut off the mower and trace the leak to its source. Remove engine covers or shrouds that conceal leak sources. Leaks that persist when fasteners are tight may indicate a failed gasket.

The Deck

• Most push mowers, and some rider mowers, have an engine oil drain plug under the deck or frame. Remove the spark plug(s) to safeguard against the engine starting by accident. Get under a rider, or lay a push mower on its side, to view the drain plug. Plugs that leak need to be removed for repair or replacement, and most or all of the engine oil will drain out. Replace a stripped plug, but slightly worn plugs may seal well after the threads are wrapped in plumber's tape.