**Always follow the instructions in your repair manual when doing repair or maintenance work on Outdoor Power Equipment. Manuals can be found at the manufacturers website.**
In this video I show how to check if your lawnmower engine is creating a vacuum in the engine’s crankcase when the engine is running. When the piston moves up and down, the crankcase volume is constantly changing. This change causes the crankcase pressure to change, but because the crankcase breather valve will let gases in the crankcase escape, but not let air in, the pressure in the crankcase should be less than the ambient pressure.
If your crankcase breather valve is not working correctly, it can cause the pressure in the crankcase to rise. Also, a worn engine will let combustion gases escape past the piston and enter the crankcase. This is called “Blow By” and will cause the pressure in the crankcase to rise.
Increased pressure in the crankcase can cause excessive oil consumption as well as other problems.
Thanks for watching!