What can cause excessive heat in a hydraulic system?

Excessive heat in a hydraulic system can be caused by multiple factors that relate to the system's efficiency and operation. When oil bypasses a filter, it can indicate that the hydraulic fluid is not being properly cleaned or that there is an obstruction causing a restriction in flow. This leads to the pump working harder than necessary, generating excess heat due to increased friction and pressure.

Additionally, if a relief valve is stuck partly open, it can cause hydraulic fluid to circulate inefficiently. The relief valve is meant to direct fluid back to the tank when pressure exceeds a certain limit, but if it remains partially open, it can lead to fluid being pumped at an inappropriate rate, again resulting in additional heat from the hydraulic components working harder than designed.

In summary, both the bypassing of oil through an unfiltered path and the malfunctioning relief valve contribute to an increase in temperature within the hydraulic system, leading to the selection that encompasses both of these scenarios as a possible cause of excessive heat.