2-11
FLUSHING THE HYDRAULIC SYSTEM 2.7
Contamination in the hydraulic system is a major cause of
component failure. Contamination can enter the hydraulic
system in any of the following ways.
1 When draining the hydraulic system.
2 When disassembling components.
3 Making auxiliary connections with dirty couplers.
4 Normal component wear.
5 Component failure
There are 2 types of contamination, microscopic, or non
visible, and visible. Microscopic contamination is sus-
pended in the fluid and moves freely through the
hydraulic circuits. Examples of problems caused by
microscopic contaminates include the following:
1 Cylinder rod seal leaks.
2 Control valve spools do not return to neutral.
3 Hydraulic system has a high operating temperature.
4 Components wear rapidly.
Visible contamination is foreign material that can be
found by sight, touch or odor. Some examples of visible
contamination include the following:
1 Particles of metal or dirt in the oil.
2 Air in the oil.
3 Odor of burned oil.
4 Water in the oil.
The best way to remove contaminates from the hydrostat-
ic drive system is to disassemble each component and
flush and clean thoroughly.
The hydraulic control circuits may be cleaned by attach-
ing a suitable hydraulic filter to the auxiliary couplings
and circulating the fluid through it.
General Information
Contamination Types