Having a weird issue, noticed a few times hydraulics were jerky on my Volvo 210 mostly when boom down sometimes there is pressure in the tank others times not. I checked it about 5 times yesterday and it had pressure everytime except for the last time? I just hit the button for a half second to hear if air is going to come out to check. Issue just started after I replaced the filter in the breather, i've taken it apart and compared it to one on my mini and everything looks fine. I was going to try swapping it with the one from my mini but I don't get why it would hold sometimes and not others it doesn't make any sense?
Good day The pressure is self generating from the differeing displacement of the hydraulic cylinders, by fully stroking the arm and bucket you should get about 14 p.s.i. Attached may be helpful. Jerky hydraulics only on the boom down suggests that is where the issue originates, testing iin "F" mode when the problem is active my give a clue as to the source. Kind regards Uffex
When I deliver a new machine to a customer I would tell them that before putting the machine to work and when the oil was cold to cycle the boom and stick functions to the ends of their stroke. The would charge the tank air pressure. The pressure cap is the only thing I can think of that would affect the residual air pressure in the tank.
That's what I figured it was just confusing the way it would be pressured then the next minute not. Like friday at end of day it wasn't, but this morning it was? But after running it for an hour it wasn't pressured anymore. I'm 99% sure it's just got to be something wrong with the cap and it's not holding pressure, dealer wants $150 for a new one will take it apart again and see if anything looks wrong.
Good day That is a very common part to many excavators may be wise to research the price. Kind regards Uffex