🔍 Key Concepts

• Lube oil system flow path: sump → pump suction → pump discharge → cooler/filter → lube oil header → engine bearings • Effect of air leaks on pump suction vs. discharge pressure • Difference between a restriction in discharge and a loss of suction on system pressure and flow

💭 Think About

• Trace the lube oil from the sump through the pump and into the header: where would a problem cause the entire header pressure to drop unusually low? • Think about what happens to pressure if a valve is stuck closed: would that make pressure higher or lower upstream of the valve? • Consider how air entering the system before the pump affects the pump’s ability to build and maintain pressure in the header.

✅ Before You Answer

• Identify whether each choice would affect system pressure upstream or downstream of the problem point • Decide which condition would cause a general loss of pressure throughout the header, not just at one local component • Check which option would most likely cause the pump to lose prime or cavitate, leading to low header pressure