What this test proves

Screen coolant-system vapor for combustion-gas contamination. A negative result may miss an intermittent leak.

Tools

  • Compatible combustion-gas detector and fresh test fluid, or approved gas analyzer
  • Correct adapter and detector instructions

Preparation and precautions

  • Start with a cooled, depressurized system and install equipment by its instructions before the required warm-up. Never remove a hot cap.
  • Use ventilation and protect against hot coolant. The sampling device must not ingest coolant.

Connections

  • Sample vapor at the approved filler/expansion-tank point through the detector; maintain the required separation from liquid coolant.

Equipment settings

  • Use the specified fluid, sample duration and engine conditions; interpretation depends on detector and fuel type.

Test sequence

  1. Check detector/fluid condition.
  2. Run only the prescribed conditions and draw the vapor sample.
  3. Observe the specified indication.
  4. Repeat or corroborate suspicious results using another approved test.

Expected signal / readings

Interpret only the detector manufacturer’s specified change or gas reading; avoid a universal color rule.

Interpreting results

  • A positive result supports combustion-gas entry but does not uniquely identify a gasket, head or block defect.
  • Contamination and inadequate sampling can invalidate results.

Common mistakes

  • Drawing coolant into test fluid
  • Reusing contaminated fluid
  • Treating one negative idle test as conclusive