Valve seats should be inspected for cracks before they are serviced.

Valve seats should be inspected for cracks before they are serviced.

• A. False
• B. Only after service
• C. Only if the engine overheated
• D. True

Answer: (D)

Before you service valve seats, it’s important to check for cracks because the seating surface must be solid and continuous to seal properly. A cracked seat can leak the combustion chamber and may grow worse if you grind or reseat it, leading to valve leakage, loss of compression, or burnt valves after repair. If a crack is present, the proper repair route may change—you might need to replace the seat or head rather than just reworking the seat, and attempting to rework a cracked seat can cause further failure. Cracks can hide under built-up carbon, so cleaning well and using a non-destructive test like dye penetrant or magnetic particle inspection helps reveal hidden damage. Identifying cracks upfront ensures you choose the correct repair method and achieve a reliable seal.

Before you service valve seats, it’s important to check for cracks because the seating surface must be solid and continuous to seal properly. A cracked seat can leak the combustion chamber and may grow worse if you grind or reseat it, leading to valve leakage, loss of compression, or burnt valves after repair. If a crack is present, the proper repair route may change—you might need to replace the seat or head rather than just reworking the seat, and attempting to rework a cracked seat can cause further failure. Cracks can hide under built-up carbon, so cleaning well and using a non-destructive test like dye penetrant or magnetic particle inspection helps reveal hidden damage. Identifying cracks upfront ensures you choose the correct repair method and achieve a reliable seal.