🔍 Key Concepts

• purpose of diesel engine test cocks on cylinder heads • what happens inside a cylinder after a long shutdown (condensation, possible liquid accumulation) • effect of trying to start an engine when there is liquid in the cylinder (hydraulic locking)

💭 Think About

• Ask yourself: What are test cocks actually opened to check for before starting—fuel system issues, air system issues, or something inside the cylinder? • If liquid has accumulated in a cylinder and you try to start the engine, which part of the engine is most at risk when the piston moves and cannot compress a liquid? • Which option directly relates to the dangers of hydraulic pressure inside the cylinder, rather than normal combustion or fuel/air problems?

✅ Before You Answer

• Verify what test cocks are connected to: fuel lines, air system, or cylinder space? • Consider which components (from the options) are physically inside the combustion space and exposed to high pressure when the piston rises. • Eliminate any choices that deal mainly with fuel system bleeding or valve timing/lift, since that is not the primary purpose of test cocks.