871 Hydraulic Problem

robojox · Apr 23, 2009

Okay guys a extra opinion never hurts. Well a little back ground bought a one owner 61 871 with SOS dont cringe either they work bad or good I seem to have a good one, the tractor sat for like 20 years in a barn and I have never seen condensation rust under a valve cover like that before but anyways, through a lot of work and going thru things and about 1000 worth of parts got it running and it runs good, wanted to run it around awhile before any painting to pick apart the bugs and I have one.
The 3 point was working fine and then would not work at first then quit all together, i disced with it several times no problems, well after it quit I checked prime on the pump fine, then I pulled the pump opened it maybe blockage or something only thing i found was some wear on the wobble shaft from the seal. With hyd. guage on the pump wont read anything. Tonight after work next thing is pull the bottom cover and check the pressure relief.
Any pearls of wisdom ? The only thing I thought is maybe my hyd. guage is bad and that is sending me down the wrong path.
Has anyone ever had a bad relief, I mean even it is sending everything back to tank then it seems like I would at least see a few hundred pounds on the guage or something.
Thanks ahead of time.

Soundguy · Apr 23, 2009

IMHO.. you are looking in the wrong place.

Remember.. that system uses an unloading valve.

when the 3pt lift lever is down, oil passes from the pump thru the valving right back to sump.

My guess is that your unloading valve is stuck / sticky.. probably from dirty oil.

Normally you could check pressure by chaining the 3pt lift arms down to the axles, plumbing in a gauge at the option cover ( 3x5 cover with a big ole pipe plug in it ) and then rais the lift lever and see wht pressur ethe pump was making at relief.

with yor results of no pressure, then that makes me think oil is going right back to sump.

If it was me.. I'd drin the oil, flush with some diesel and work the 3pt handle, then refill with clean oil and see what you have.

If that didn't do it, I'd pull the lift cover... just pull the bolts around the edge and disconnect the 3pt linkage and she pops right off. The kit of orings and the gasket costs about 13 bucks at your dealer or online.

Up until a year ago I had only 'helped' do one 00/01 hyd cover, and then had to do the top cover on my 660. With a lil info from the smart guys like RickB, and a couple other posters, it was really.. no problem, way easier than i was expecting. I've rebuilt 9-2-8N covers and pumps before no problem.. but the 00/01 cover is different.

In any cases.. it just wasn't a real bad job.. mostly cleaning and reoringing .. etc.

if you are fast and the 3pt linkage doesn't fight you coming apart.. i figure a 2 hour job start to finish.

Hopefully the flush and refill will get you going..

post back what you find after the flush.

soundguy

robojox · May 4, 2009

Well sorry it took awhile to get back to you all had to go to Lansing for Gm.
Did what you suggested Soundguy, I had already changed the oil twice but it was still a little milky so a good suggestion on the diesel fuel, did that and got the system to work on diesel fuel ran it that way, just sitting no load or anything everything worked fine, I also pulled apart the valve under the seat and cleaned it pretty dirty. Drained the fuel and refilled with fresh hyd. oil worked but was jerky coming up then let it sit for a day and it did not work again. Well gonna go back to the fuel again and the relief valve maybe it isnt as clean as it needs to be.
Soundguy if I understand you correctly the hyd system is a meter out system? And does anyone know system pressure I read somewhere that the relief doesnt work till 2000 psi is the correct?