Lawn Tractor: Blows White Smoke From Exhaust

If the engine is liquid cool, the main cause of white smoke is a blown head gasket. The head gasket creates the seal between the engine block and the cylinder head for compression and provides a tight seal for oil and coolant passages. To check for a blown head gasket simply remove the spark plug. If the spark plug is bright and shiny, you have coolant entering the cylinder. The coolant burns off at a high temperature, acting as a steam cleaner inside the combustion chamber. The head gasket at this point will need to be replaced. To do this, begin by draining all fluids. Next, remove the engine cover, fan, and fuel pump. Remove the carburetor and muffler from the cylinder head and remove the valve cover bolts and cover. Now you can pull the valve cover off. Remove all the bolts holding the cylinder head to the engine block, remove the head, and pull off the old head gasket. Clean both the surfaces of the engine block and cylinder head with a soft brush. Be careful not to damage these areas, as you will need a tight seal for the gasket. At this point, you can install the new gasket and reassemble. It’s best to replace all the cylinder head bolts with new ones as they are usually designed for one-time use. Replacing the cylinder head bolts will help you avoid a second blown head gasket. You will want to check your manufacturer’s specifications for the bolt-tightening sequence, and how tight they must be for the head gasket to provide even compression. These bolts must be torqued for a proper seal. Once this has been completed, you can re-install the carburetor, muffler, and valve cover with a new valve cover gasket, fuel pump, fan, and cover.