790 dlc excavator

Hey I have a 790d lc excavator, and when i try to lift the main boom slowly my lever vibrates. When I pull the lever all the way it stops vibrating. It usually starts while I'm operating more than one control at a time, also it seems it gets worse as oil heats up

Deere/Hitachi had a solution years ago that mentioned if a pilot hose was replaced with an incorrect type hose it could cause normal vibrations to be felt in the handles -- If someone used a standard high pressure 4wire 5000 psi 1/4" hose instead of the recommended cloth braid 1000 psi rated hose it could cause this issue as the normal pulsations in the lines are normally absorbed by the more flexible hose. Maybe look if any of the pilot lines look to be different -- if so, you could swap at both ends with another function (boom down?) and see if the symptom migrates to that function.

They are called Synflex lines I recall. I heard it also said not to use the regular high pressure hoses 20 plus years ago . Hopefully the hydraulic tank is full, that would be the first fear. The pilot system only pushes 400psi through it.

JonathanMA said:

Deere/Hitachi had a solution years ago that mentioned if a pilot hose was replaced with an incorrect type hose it could cause normal vibrations to be felt in the handles -- If someone used a standard high pressure 4wire 5000 psi 1/4" hose instead of the recommended cloth braid 1000 psi rated hose it could cause this issue as the normal pulsations in the lines are normally absorbed by the more flexible hose. Maybe look if any of the pilot lines look to be different -- if so, you could swap at both ends with another function (boom down?) and see if the symptom migrates to that function.

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I've seen single wire hose do it, needs to be synflex.

Thanks for the advice, ill check that out. I did replace two hoses but not with synflex just with standard hose. Although, my problems are now progressing, I overhauled the motor in my excavator and so I had to take the pumps off. When I had everything back together I just filled my hydraulic tank with oil and figured gravity would do its thing and fill the pumps with oil, didn't no to prime them. I ran it for a week and found out I was supposed to prime them. So I took the plugs out and there was almost no oil in the pump so I filled it up and cycled the hydraulics. Then, I took the plugs out again to see if they were empty and they were. Are they always supposed to be topped off with oil or is that normal. If not normal, any idea what the problem could be. They seem to be chattering at times too ( it comes and goes), especially as the oil warms up.

The reservoir oil level is higher than the pumps so those pumps should always be full. Has the suction screen in the tank been checked? The vent filter inside the fill cap? Those machines build pressure in the reservoir under normal operation. When they cool from sitting the fill cap allows air in, hence the filter.

I did have the suction filter out seemed to be in good condition and clean. No, I haven't checked the filter in fill cap Ill check that out.