Which of the following are typical signs of a blown head gasket in a diesel engine?

• A. Exhaust smoke is black only.
• B. White exhaust, coolant loss without external leak, oil-coolant contamination, or reduced compression across cylinders.
• C. Radiator leaks oil.
• D. Engine runs perfectly.

Answer: (B)

A blown head gasket lets coolant or oil slip into the combustion chamber or mix with the oil, and that shows up in several clear ways. White exhaust indicates coolant entering the combustion chamber and flashing to steam, which creates visible white smoke from the tailpipe. Coolant loss without any external leak happens because the coolant is escaping internally rather than out of the radiator or hoses. Oil–coolant contamination means coolant is mixing with the engine oil, which can be seen as a milky appearance on the oil dipstick or filler cap and can clog bearings if not addressed. Reduced compression across cylinders occurs because the gasket breach prevents the cylinder from sealing properly, so each affected cylinder shows lower pressure and lost power.

Other scenarios, like exhaust that’s only black, usually point to other issues such as an overly rich fuel mixture or excessive soot; radiator leaks oil aren’t typical indicators of a head gasket problem, and an engine running perfectly would not align with a gasket failure.