What you are describing sounds like an obstruction somewhere between the suction tube in the tank and the inlet of the pump. If so, then blowing air back through that path might not have sufficient force to dislodge the obstruction. 12:25 As much as you loosened that nut, I would expect the hydraulic fluid to be spraying out at high pressure not dripping out. If it does not have an adequate volume of hydraulic fluid flowing then the problem is before the valve control body. I would also make sure that you have the correct hydraulic oil filter. I'm not an expert but that's my $0.02.
I see below you found the issue but I'm still going to pass on what I know about these as I have a 371 and have been through the entire machine multiple times. There is a very large flaw in the design of the hydraulic system, being that its a single gear pump without an integeral precharge section to consistently provide flow to the high pressure side. It will be very sensitive to even the slightest restriction on the inlet. Filter maintenance is of absolute importance on these as the oil is also used to lubriate the entire chain and clutch drive system and there is a never-ending supply of contaminants. The hoses used on the inlet side of the pump must also be vacuum rated as they can collapse end cause cavitation which will destroy the pump in minutes. Most guys fit in pieces of hard tubing on the inlet side of the pump and just use hose and clamps as couplers. These things are known for killing pumps in hot weather when the hoses go soft and continuously starve the pump.
I would check the vent cap on your hydraulic tank it sounds like it's creating a internal vacuum like it's not venting and that could be causing your lack of hydraulic it's just a guess on my end
Tank has a item suck in suctions hose at fitting, eather in side tank or outside, if it had a crack or pin hole it would not suck in hose Remove tank filling cap and try it Also locate and clean tank vent
Regarding the suction tube inside the hydraulic oil tank, is it possible that you have a pin hole inside the suction tube (above the hydraulic oil level) causing it to suck a lot of air?
Check psi and psi relief valve You need gauge to check system Was the old pump destroyed ?? If so there’s metal in tank, line and hose Surely you drain the tank and cleaned it out ??? Remember hyd psi can kill and go thru a hand or body
If the concern is foreign material running through the system, it might be a stuck directional control valve. might be worth it to take it apart and re-seal. they have little to no tolerance for even the smallest bit of Grit. and if its old and worn out might not be traveling back and forth Straight anymore and may become lodged halfway between its intended directions and if the o rings are bad in them that maybe the jerking part.
Good call but yes. I drained the whole sump area out. There was a little bit of sludge in the bottom but not to bad honestly. Once I cleaned it out I put diesel in it to finish cleaning it. I also blew air backwards through the screen as best as I could. Then I dried it out and put the clean oil back in.
I know what it is!!! Its the Filter change out the filter again and all those problems are fixed. I know its a new filter but it must have sucked something through the lines and clogged the new filter
The wires broke off of my clutch magnet and they were only held on by the insulation sometimes touching and making it pulse the hydraulic pump like that
It actually turned out to be the brand new hydraulic filter. I opened up the new old one and didn't see anything clogging it. But put a new filter in and it's been working perfect since then.
I have one as well kinda had same problem i rebuil my jacks and fixedvit thwre held and never leaked either not ahure if one was bypassing or what maube adjust pedels to oush or pull rod farther
Also changed my filter as well it had a new one on too I got my 310 all tore apart lk urs was put to gether and had similar prob so either jack rebuilding or filter or may e just air in system fixed mine gd luck
