🔍 Key Concepts

• Crankcase pressure and what causes it to increase • How piston rings and cylinder liners control gas blow‑by • Whether lube oil pressure or relief valves are normally connected to crankcase pressure changes

💭 Think About

• Which component, if worn or damaged, would allow combustion gases to leak past the piston into the crankcase? • Would correctly seated new rings normally increase or decrease crankcase pressure? • Does a cylinder relief valve failure change pressure in the cylinder, the crankcase, or somewhere else?

✅ Before You Answer

• Be clear on what space the crankcase is and how it is ventilated • Match each answer choice to whether it directly affects gas leakage into the crankcase • Eliminate any options that only affect oil pressure or cylinder safety but not crankcase pressure