Practice question

During in-chassis valve service on a school bus diesel, a valve is found with a burned, eroded face. The MOST likely cause that should also be investigated is:

  1. Too much valve lash and a cold-running engine
  2. A new air filter
  3. Insufficient valve lash, poor seat contact, or excessive combustion temperature preventing the valve from sealing and cooling
  4. Fresh engine oil

Answer: C — Insufficient valve lash, poor seat contact, or excessive combustion temperature preventing the valve from sealing and cooling

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Practice more: ASE S2 Diesel Engines (School Bus) Practice Questions - ASE S2 - Diesel Engines (School Bus) Certification Exam →