Jinma 254 hydraulic Question

[freetrapper]

Ok, I have rebuilt all 4 lift cylinders on loader, replaced the steering cylinder and rebuilt the 3point lift cylinder, cleaned and flushed the systen put on a new filter, all went good and worked perfict after that for about a week. Did quite about of work with the loader and even mowed for about 4 hours one afternoon, it rained for three days so it set for about four days now the last two times I have used it has belched fluid out of the over flow lost maby a quart both times. Anyone have any Ideas? Also might mention the last time I used it before it started this I noticed it dripping a small amount of oil from the pump housing so I snuged up the pump mounting bolts and that stoped the leak don't know if that had anything to do with this or not. HELP!

 

[RonMar]

The system has a certain total volume. If somehow air is replacing fluid anywhere in the system, that air being pumped thru the system could cause the reservoir to overflow untill the air is purged. Is it jerking or operating erratically at any point? That is an indication of air

Tell me about this filter? Is it a spin-on cartridge down on the right side of the tractor between gas pedal and hydraulic pump? If so a better term would be a strainer as it is on the suction side of the pump I am guessing...

Also what type fluid are you running in this hydraulic system? Should be AW-32 in most cases unless you are in some temperature extreme environment.

Hydraulic pumps are great at pushing fluid, not so great at sucking fluid. IF that "filter" is as I described, you need to be carefull of the specifications for it. It should probably be a mesh strainer core(#100 mesh) specifically designed for suction side applications. If it is too restrictive, it will cause the pump to cavitate(does damage) and to also pull air in thru any weak spot in the system like the pump O-rings or the O-ring seal on that spin-on cartridge. IF the pump got noisier after the filter change, and/or under load, that is one giveaway that the filter may be wrong...

So what could be happening, upon startup when the fluid is it's coldest/thickest, is that the pump cannot suck it thru the filter, and is drawing in air from somewhere along the line or a cracked pump housing/bad seal(you mentioned an oil leak on the pump?). It is pumping air instead of fluid and that air bubble is pushing all the oil in the pipes hoses and control valve and diverter ahead of it into the reservoir without drawing any fluid out which causes it to overflow untill the system starts to draw from the sump then you are low(minus the fluid you burped). Of course if you operate a control lever while this is happening, air will get cent to that cylinder causing erratic/jumpy operation untill that air is purged thru operation...

 

[quicksandfarmer]

Have you been operating on a hill? Some people report that the overflow overflows when the tractor is tilted.

 

[freetrapper]

I should have said strainer its the stock screen in the tank, I am using aw-32 fluid, it is a little jerky when at an idle but not if you rev it up a little. Does it have o rings or a gasket at the pump mount? Its funny though it was not doing this before I tightened up the pump.

 

[freetrapper]

Not really its pretty level where I have been useing it

 

[RonMar]

Is there a pipe union between the sump and the pump? That is a prime place for a suction side leak. There should be an O-ring seal where the suction pipe attaches to the pump. The pump housing seals are inside the pump housing between case and end cover, there is just a gasket between the pump and the gear case where the pump mounts as it is only sealing in motor oil at that point. Oh and there is a shaft seal on the front of the pump...

 

[freetrapper]

No pipe unions and I have checked the strainer to make shure it is still tight also replaced the o ring at the pump still acting up. thanks for all the suggestions guess I need to order a pump its the only thing left I will take it off and tear it down today to check it out.

 

[freetrapper]

Pulled the pump the other day and found the front seal cocked and about ready to fall out should have put new seals in it when I done the rest of them all is good now. Thanks again guys for all the help and If it had not been for the guys at Affordable I would have spent a ton of money on a pump and only needed to put a seal kit in it they are the ones to call.

 

[RonMar]

Glad you found it.

With the seal in front gone, did you "grow" any motor oil?

 

[freetrapper]

It was about half a quart over full when I drained it and changed the filter I think it was mostly pumping crank case pressure into the hydraulic system that is why it kept belching all the fluid out.