Priming an empty hydraulic system

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Tazza

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Ok, i am pretty close to finishing my third restored/painted 743. One thing i thought others may be interested in is re-priming the hydraulic system. When i removed all the parts i drained ALL the oil from the pumps/hoses/tubes and cylinders. One idea i came up with was when i re-attached all the hoses and the lift cylinders is to fill the oil tank then pull the rods on the lift arms out and activate the pedal (this requires 2 people). It will draw up oil from the tank, i did it back and forth a few times full stroke to try and get as much oil in as possible. I even noticed that rolling the machine around it would get stiff from the motors filling with oil too. Started it up and i had instant hydraulics available, full of air but it shows the oil made it to the pump.
Just something others may find useful.
 

TriHonu

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Thanks for the tip!
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I just got back home from an engine/hydrostatic install. The hydraulics were not totally drained but had significant air in the system. We blocked the machine up off the floor pulled the sticks forward and turned the wheels until we has so much pressure two of us couldn't turn them.
When we fired the engine we had instant drive power and upon cycling the lift/tilt two complete cycles there was almost no noise in the hydraulics at all. There is still some foam in the hydraulic tank so there is still a little air in the system but not enough to affect operation.
 
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Tazza

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Thanks for the tip!
I just got back home from an engine/hydrostatic install. The hydraulics were not totally drained but had significant air in the system. We blocked the machine up off the floor pulled the sticks forward and turned the wheels until we has so much pressure two of us couldn't turn them.
When we fired the engine we had instant drive power and upon cycling the lift/tilt two complete cycles there was almost no noise in the hydraulics at all. There is still some foam in the hydraulic tank so there is still a little air in the system but not enough to affect operation.
It took a while for my arms to move smooth. I have cycled them 2-3 times a day each for say 5 minutes for the last 4 days. They seem rite now but when i attach the tilt ram i need to purge it too! My oil is still a little foamy too, it will clear up in time. You were lucky you got the oil through so easily. Thats the beauty of not draining the whole system..... Its still easier working when there is no oil pouring out of everywhere.
 

skidsteer.ca

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Jan 20, 2006
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3,853
Thanks for the tip!
I just got back home from an engine/hydrostatic install. The hydraulics were not totally drained but had significant air in the system. We blocked the machine up off the floor pulled the sticks forward and turned the wheels until we has so much pressure two of us couldn't turn them.
When we fired the engine we had instant drive power and upon cycling the lift/tilt two complete cycles there was almost no noise in the hydraulics at all. There is still some foam in the hydraulic tank so there is still a little air in the system but not enough to affect operation.
Both good ideas.
Anything that can be done to make the functions move easy will lower the pressure required to pump the oil through the system. Less pressure less wear from cavititaion while the air to escapes to the reservoir.
I have done the reverse with cylinders when repacking them. Lift the boom to the top and chain it up with the hoist. Pull the pin on the rod end of the cylinder, unhook the hose on the top of the barrel and use compressed air to push the rod back in while holding the boom function in lower.
Then when you take the cylinder apart it is almost empty. Much less mess.
Ken
 
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Tazza

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Both good ideas.
Anything that can be done to make the functions move easy will lower the pressure required to pump the oil through the system. Less pressure less wear from cavititaion while the air to escapes to the reservoir.
I have done the reverse with cylinders when repacking them. Lift the boom to the top and chain it up with the hoist. Pull the pin on the rod end of the cylinder, unhook the hose on the top of the barrel and use compressed air to push the rod back in while holding the boom function in lower.
Then when you take the cylinder apart it is almost empty. Much less mess.
Ken
I like that way too, saves al the time getting the air out!
My main concern was no oil was in the pumps. With me drawing the oil into the rams meant oil MUST pass through the pumps to reach it.
 
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