Which statement best describes externally restricted CAC in relation to engine damage?

• A. Externally restricted CAC can cause piston crown cracks
• B. Internally restricted CAC can cause piston crown cracks
• C. Both types equally cause cracks
• D. Neither type causes cracks

Answer: (A)

When cooling performance is limited at the outside of the charge air cooler, the cooler can’t reject heat effectively. That means hotter charge air enters the cylinder. Higher intake air temperatures raise the combustion and cylinder temperatures, increasing thermal stresses on the piston crown with each heat cycle. Over time, these thermal stresses can initiate and propagate cracks in the piston crown. That direct link between external restriction and elevated piston temperatures is why externally restricted CAC is the best description for causing piston crown cracks.

Internally restricted CAC would affect cooling flow inside the cooler itself, but the impact on piston crown temperature is less direct, making the external restriction the more likely cause of cracks.