TM 5-3810-300-24 & P2
Air in Oil Circuit.
Air in the sircuit can be due to low oil supply in the reservoir which will cause pump to suck air in with the oil.
It can be due to air leaks into the circuit elsewhere.
A leaky pump shaft seal can allow air to enter the system.
If installation has "separate reservoir"--look for "kinked" intake hose. This will cause excessive vacuum pull on pump intake
seal.
For bleeding the air from the oil, see bleeding instructions.
If the air cannot be bled out, the cause of the air in the circuit must be determined and corrected.
Filling and Air Bleeding Procedure for Power Steering Systems.
Most power steering systems today must in essence be self-bleeding of air, provided sufficient oil is available in the system
so that the air may be replaced by oil without further air entering the circuit. Some systems in use will eliminate air much
more rapidly than others with no special precautions or aid. The following suggestions are intended to expedite the filling
and air bleeding of the circuit.
1. If the system has been completely drained of oil (or the cylinder empty):
a. Fill reservoir "full"
b. Start engine but be ready to add oil as soon as the engine is started and is running at idle.
c. Maintain a "full" reservoir by adding oil as necessary for a minute or so without turning the steering wheel. This
allows the large air bubbles in the lines, etc., to escape.
d. Slowly steer the wheels avoiding any abrupt changes of speed or pressure. (To be done with engine idling). Add
oil as necessary to maintain a "full" oil level. Four or five turns of the road wheels (stop to stop) are generally
enough to eliminate most of the air from the cylinder.
NOTE
AT THIS POINT, SOME SYSTEMS WILL HAVE ELIMINATED PRACTICALLY ALL THE AIR FROM
THE SYSTEM, WHILE OTHERS WILL RETAIN A GREAT DEAL OF AIR IN THE OIL, GENERALLY IN
FORM OF VERY SMALL BUBBLES AS EVIDENCED BY CLOUDY OR CREAMY APPEARANCE TO
THE OIL. IF THE OIL IS CLEAR AND THE STEERING IS NORMAL, ADJUST OIL LEVEL IN
RESERVOIR TO RECOMMENDED LEVEL AND SECURE THE SYSTEM. IF THERE IS ANY DOUBT
OR IF THE OIL SHOWS AIR TO BE PRESENT, PROCEED AS FOLLOWS:
e. Allow the engine to run at 1000 to 1500 rpm's for a few minutes, steering the system from stop to stop about once
every minute. (Intermittent steering action allows the air to form rather large bubbles in the cylinder which are
easier to expel from the oil when they reach the reservoir). Continue this procedure until the oil is clear, adjust oil
to recommended level and secure system.
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