DTC DTC Diesel Engine Lubrication Systems 1

Question 1

What is the primary function of the engine oil pump in a diesel engine's lubrication system?

Accepted Answer

To circulate pressurized oil to all engine bearings, journals, and moving components

Answer

The oil pump creates the pressure needed to force oil through the entire lubrication system, preventing metal-to-metal contact on bearings and journals.

Question 2

A diesel engine's oil pressure warning light illuminates at idle. What is the FIRST diagnostic step a technician should take?

Accepted Answer

Verify actual oil pressure with a mechanical gauge to confirm the reading is accurate

Answer

Always verify low oil pressure with a mechanical gauge first, as a faulty sending unit or gauge can produce a false low-pressure warning.

Question 3

What does a diesel engine's oil cooler primarily do?

Accepted Answer

Removes excess heat from the engine oil to maintain proper viscosity and protect components

Answer

The oil cooler uses coolant to remove heat from the engine oil, preventing viscosity breakdown and protecting bearings and seals from thermal damage.

Question 4

Which viscosity grade of engine oil is most commonly specified for heavy-duty diesel engines in warm climates?

Accepted Answer

SAE 15W-40

Answer

SAE 15W-40 is the most widely specified viscosity for heavy-duty diesel engines in warm climates, providing proper film strength at operating temperatures.

Question 5

What is the purpose of the oil pressure relief valve in a diesel engine lubrication system?

Accepted Answer

To limit maximum oil pressure and protect bearings and seals from excessive pressure

Answer

The pressure relief valve opens when oil pressure exceeds the maximum rated value, bypassing oil back to the sump to prevent damage to gaskets, seals, and bearings.

DTC - Diesel Technician Certification Practice Test

DTC - Diesel Technician Certification Practice Test

DTC DTC Diesel Engine Lubrication Systems 1