Hydraulics just not enough

You can easily remove the side plate where the dipstick is and check your lift piston. When under load, if you see a stream of oil coming out of it your problem is only a $10 set of lift seals and a couple of O rings for the hyd fluid ports on the side of the housing.

Clearances in the pump are on the order of .0001 of an inch (piston pump anyway, vane shouldn't be any different other than cover leaking around the ends of the vanes.) The vanes are made out of high tensile tool steel. Conversely, the lift piston seal is a rubber O ring with a leather or plastic backup washer, and it is attempting to seal against a 45year old cast iron cylinder. Which would you expect to cause the most trouble?

Now that I am thinking about it, some of these old time experts have posted solutions to vane pump problems that aren't that expensive.

I'd still get a 5000# gauge and check the pressure before I'd even lift a wrench for the pump. The're only $10 to $15 and available at good auto parts jobbers or Northern Tool carrys them. Get one that is oil filled and it will dampen pulsations, making it easier to read and save damaging it. Expect pump pressure to follow tractor rpm's until pressure is high enough to activate the press rel valve which is at about 2600 psig.

Peek at the lift cyl first. That costs you nothing but time and a little RTV to put the seal back and you don't have to go and get anything.

txblu

Question: How do you check the pressure? I'm envisioning something that threads in somewhere, but I can't figure out where that would be?

TIA ...
~ja

Stay with us till you get your problem solved. Looks like you have a good following on this post.

Best,

txblu

My local NH dealer is excellent in stocking these parts for the smaller 50 (+/-) year old tractors. Lots of 5 acre "farms" here. Examples I can recall is the lift piston repair kit is ~$10 and the 2 seals for the hyd line on the top side of the casting are under $1. I usually clean the big top gasket and put a thin coat of RTV on it before reinstalling or they have them if you need a new one. Since I keep my equip shedded I don't worry too much about water injestion.

Just a minute. Gotta go out to the shop and get my I&T manual to answer your question.

I'm back. Toward the front of the main casting, of which the lift cylinder is part, and under the this cyl is the "control valve" This valve is linkaged to the lift arm. When you move the lift arm to raise/lower implement, linkage moves this valve and it forces oil into or outof the lift cylinder.

The tolerances on this "machine tool steel" sucker are as tight as in the pump. There are no Orings in it. It is a pure friction fit and usually is coded to get the correct dimensions to mate with the casting. Reason is it is shuttling 2500 psig fluid to and from the lift cylinder.

It appears that fluid could in fact leak from the lift cylinder, around the casting and over to this valve (beneath it and slightly to the side)and appear to be coming from the control valve.

The only thing that you could do to this valve instataneously (as you said your malfunction occurred) (1)is to break the linkage btween it and the lift arm. You can inspect this linkage from your peer hole also and upon moving the lift arm you should be able to see the linkage move back and forth. If broken parts will be dangling.

(2) There is a small spring in the bottom of the casting which forces the "control valve" outward against the linkage so it will follow your movement in and out. This could be broken. But I think if it broke, the c valve would go to the most inward position and your linkage would fall off the end of the valve and just be dangling.

Looks like both problems associated with the control valve would result in visable linkage dangling.

But this is NOT the case as you said you can lift the arms up and down without a load. This c valve is not your problem.

Get yourself a set of seals for the lift piston!

That makes sense.

Yes the pump is more robust that a lot of folks give it credit (my opinion). Course 50 years of pumping crud could take it's toll if the owner didn't maintain clean fluids.

TIP. The best way to get the piston out is to remove linkages to get at the connecting rod (which just falls out of the piston). Be careful not to turn any adjusting nuts if you are happy with the lift action (other than it won't lift a load. This way you can put it back together and not have to adjust anything. When you see that it is clear that the piston has room to come out, put compressed air (about 40 psig is plenty) into the housing inlet port in spurts, where fluid would come up from the side of the casting (front hole is pressure and rear is fluid return...use the front hole) The piston will be forced out into your hand.

Once removed, there are 2 rings to be aware of. One is the Oring (about 3" in dia) and adjacent to it is a backing washer. It may be leather or recently they started using plastic. The backup washer is toward the skirt of the piston and keeps the 2500 psig from blowing the Oring out.Put the backup washer on first and the easiest way is to put the piston down on the work bench with the crown (not the skirt) up. Be careful not to score any parts with the sharp edges of the piston including yourself.

If you get a kit with leather,soak it in water till soft and pliable and get someone to help you install it. Takes 2 sets of hands as it is a snug fit. the plastic is concentric rings that just thread on like putting keys on a keychain ring.

Dry the water off the leather best you can and slop everything up good with trans/hyd fluid.

Then after reinstallation, bleed the air out.

Piston pump, remove the hex Allen screw on top of the pump and idle the tractor until solid fluid comes out. Put the plug back while fluid is coming out. Then up and down on the lift control half a dozen times or so and you should be in business.

Good luck

Mark

I believe your 860 has 3 separate compartments. Transmission,hydraulics and rear end. Did you drain and refill all 3? But check hydraulic pressure first.

steve

steve