Failure due to dieseling can occur in hydraulic systems. Dieseling occurs when air becomes trapped in the hydraulic fluid. Problems arise during high pressure situations when the gas becomes compressed, with a resulting increase in temperature.

If the hydraulic fluid (or lubricating fluid) is flammable, the increasing temperature can reach the combustion point, setting off a series of miniature explosions. As a result of these explosions, the seal is burned, leaving it with a black, charred appearance and burned surface pits. Figure 130 is an illustration of O-ring failure due to dieseling.

“The seal is burned, leaving it with a black, charred appearance.”

Figure 130