HYDRAULIC SYSTEM TROUBLESHOOTING GUIDES
(Sheet 2 of 2)
1. High oil temperature, 2100F. (990C) or above, begins to harden and erode the cylinder wiper seals. Faulty seals allow air and usually dirt to enter the
hydraulic system. Entry of dirt and air into the system occurs at the rod end of the cylinder, because of the partial vacuum formed when lowering a load. If
the filter is clogged, or if the dirt particles are small enough to get past the filter, they will cause wear in the pump.
2. Cavitation is caused by a restriction to the flow of oil on the suction side of the pump. This causes a condition in which the pump's capacity is greater than
the supply of oil available to the pump. A small restriction causes a partial vacuum which results in bubbles in the oil. The action of these bubbles striking
the pump components is to cause erosion of the components. A large restriction will decrease the lubrication of the pump, causing friction and heat in the
components. As the temperature increases, the tolerances will decrease and the pump will seize. Cavitation is characterized by a high pitch whine that
increases in intensity as the pump rpms increase.
3. Aeration arises from the same problems as cavitation, but the small bubbles have air in them. One source of air may be a leak in the suction side of the
pump. Another source of air may be the result of high oil temperature hardening and eroding the cylinder wiper seals. Aeration is characterized by a sound
like the pump is pumping marbles.