loss of power steering

[Gramps in NM]

2005 Dong feng df254G relabled as taskmaster 425A. Tractor has one common sump and two hydraulic pumps, one side mount and one front driven.
Yesterday morning used machine about two hours, all was well. Parked tractor and hosed off dirt prior to parking in garage. Ate lunch and started machine to put in garage and NO power steering. Did get it inside though. Lifted front end with bucket and placed on jack stands. Engine off, the steering works with some effort but does not appear to be binding.
All other hydraulics work fine, fluid level OK. Steering cylinder connected as it should be but needs boot.
Questions:
I plan on disconnecting the steering cylinder (will oil run out with engine off-how much?) and then starting engine to check flow. Is this a good first move?
Not sure where to go from here. All help accepted with thanks

[greg_g]

Does your front pump draw fluid from the common sump (tranny/rear diff/hydraulics)? or does it have it's separate little sump up front? Like automotive power steering. If it draws from the common, gravity will force a lot of fluid forward from the common sump - unless/until you tie the hose up higher than the fluid level. If it's got it's own little sump, you'll only lose what's in the PS sump (reservoir). In the case of the former, that's a LOT of fluid. If it's the latter, you can catch it in a clean container.

And is the front pump belt-driven? or gear-driven off the crank?

//greg//

[Gramps in NM]

Hi Greg, thanks for the reply. It's shaft driven off the crank, and the shaft does turn when the engine is running. Very difficult to see in there but it does not appear to have it's own supply. In tracing the lines there is one line that goes to the common sump from the steering valve at the bottom of the column which would also indicate a common supply. I was thinking the same thing as to all that oil coming out but also was thinking it would only come out as fast as air could displace it-no.
Still not sure how to proceed.

[RonMar]

Well if the front of the tractor is up on jack stands, you can check flow by simply starting the engine and trying to turn the wheel. Flow will be represented by how fast the wheels turn from side to side, and how much force is required by your arm to turn the wheel. But since you are not getting any power steering action, I would guess you will see no flow that way

If you can turn the wheels with the engine off, it sounds like the vane pump at the bottom of the steering colum is functioning and that there is fluid in the lower parts of the system. I would start off by tracing the fluid supply line to the PS pump and look for loose fittings. If it was working during one use and did not work the next time you fired it up, it almost sounds like something allowed the pump to loose it's prime. This could really be likley if the PS pump is mounted higher than the rest of the parts and sump? It only takes a very small hole admitting air to breakdown a fluid feed system to a hydraulic pump...

[Gramps in NM]

Had a chance to dig into things this afternoon and have found the problem. The shaft that goes from the engine to the pump has 4 ball slots in each end that seem to act as splines. On the engine side it's tight and the shaft turns, but on the pump end after look ing close I could see that the coupling that covers the balls and holds them in was NOT turning. As near as I can tell at this point I'll have to drain oil, disconnect lines to pump and pull both pump and shaft. There is not enough play in shaft I don't believe to do this without pulling pump but will know better if I can get the dang roll pin out of the shaft. It's tight and no working room.
Will try to find some one with more knowledge as to how to go about this. Still need help!!!

[TTTTTT]

In a previous thread, it looked like you had a 1 pump system with priority valve (see pics). If that is the case, the priority valve may be not functioning properly and not suppling flow to your steering gear by the steering column. Just another thought.

http://www.tractorbynet.com/forums/c...inma-y385.html

Dave

[greg_g]

In a previous thread, it looked like you had a 1 pump system with priority valve (see pics).

Pics show main pump on the right side of the engine (as viewed from the operator seat). That's for FEL, TPH, etc. Shaft goes forward from crank pulley to a 2nd pump in front of the radiator. Shaft is visible in two of the photos, just no shot of the 2nd pump. No priority valve in a 2 pump system. What you're thinkin might be a PV I'm pretty sure is the hydraulic fluid filter housing.

My bet's on the pump shaft not turning. It's probably the DF equivalent of what happens so often to Jinmas; rounding off either the pump tang or the receiver slot in the drive assembly.

//greg//

[Bob Rooks]

Ironically, an identical situation was posted on CTOA.
My response is in the thread:
Hydraulic pump coupling for a Hercules tractor | Help Me Find A Part | Forum | Chinese Tractor Owners Association

[Gramps in NM]

Have had no further chance to dig into this, maybe after church. It did seem I had only one pump at one time, but as was pointed out to dumb ol me I do have two. What may be strange is I also have priority/diverter valve. PR on side of engine and constant flow pump on front.
Thanks all, keep the info coming.

[Bob Rooks]

Gramps,
Did you read Tommy's post in the CTOA thread?

"They are listed in the parts book under hydraulics DP (Double pump) according to my china supplier they have been discontinued and no parts are avaliable".