861D Hydraulic Hickup

[MitchellB]

Today we had a load of gravel delivered and spread somewhat at our rental house driveway. I fired up the 58 Ford 861D to smooth out a couple spots in the driveway. Temperature had warmed up to about 38 degrees, and this was only about the 6th or 7th time I have started the tractor since I fixed the sheared teeth on the hydraulic pump and engine cam when I went through the engine in earlier lengthy posts. Good news is, using the heater plugs first for about 45 seconds, she fired right up just fine. The battery may need replacing before much longer (too small) but that is another story.

I noticed the lift was raising up slow. I also noticed it did not drop down as quickly as I remember it did last time I used it or fall as quick as my 8N does. It lowers slow. Odd I thought, but I barely got the engine warmed up, so I thought, maybe was the cold hydraulic fluid?

I also noticed it would hickup or burp (best word I can come up with) every 15-20 seconds when the blade was raise up and I was just sitting idling when I finished using it today. It would hickup so strong that the tractor would shake. I glanced at my hydraulic gauge I had installed on the pump and the pressure would do a quick bump up a to 80 lbs or so and drop back to the 20-30 lbs. it holds normally when implement is stationary before each hickup. Is that air in the system? Can that sudden burst of pressure be the cause of my hydraulic pump gears failure back when I bought this tractor? I have only put 2 hours on the proof meter since I did all the engine work to this, but this is the first I've notice this hickup or the slow lift and drop. Cold temperatures?

 

[Soundguy]

That very small pressure bump you see is just the system going from unloaded to actually doing something. Normally once a load is up, the check valve holds the load, and the Hyde go to unload. About 40 fish or so psi is what keeps the back pressure /unloader valve responsive. So that's your static number. When it loads the system to lift something or regenerate the circuit, there is more pressure, if you had a hay bale back there, you may see 4 digit pressures.. etc. When you have a load, even an empty implement lifted, and the 3pt handle is still up but in a neutral position, if that load leaks down, the circuit will regenerate and re lift the load.

At low rpm, pump output is lowered, however leak off will likely be load dependent. So a heavy load on low rpm may make lots of hiccups, or even leak faster than the pump can overcome. At higher rpm there is more flow, and less bumpy

Cold oil sure also can effect this. There is only so much that can pass thru the exhaust valve at a time.

Presumably you are using UTC fluid. If it is too stiff, cut it with some type f atf, or dex/merc 3 oil.

 

[MitchellB]

At low rpm, pump output is lowered, however leak off will likely be load dependent. So a heavy load on low rpm may make lots of hiccups, or even leak faster than the pump can overcome. At higher rpm there is more flow, and less bumpy

Cold oil sure also can effect this. There is only so much that can pass thru the exhaust valve at a time.

Presumably you are using UTC fluid. If it is too stiff, cut it with some type f atf, or dex/merc 3 oil.

Thanks, I think the cold was most of my problem. As you can see in the picture, the RPMs were not low (proof meter needle standing straight up) and it does have new UTC fluid in it from Tractor Supply (Traveller brand). I don't usually have much use for a tractor in winter unless the rare NC Piedmont area snow storm rolls through, so I'll probably hold off until warm weather before I try cutting the fluid with auto-tranny fluid as long as this hiccup will not harm anything for light/occasional use until then.

 

[Soundguy]

You said you noticed the 'burp' most at idle, that's where my comment came from.

UTf is generally fine, however there are cold weather UTf fluids. Since it is a seperate sump you could go with amlightnplain hyd fluid but I would not. I'd just cut with atf and sleep easy.

Neither atf cut or mild bobbing will hurt it.

 

[MitchellB]

Is that hydraulic check valve easy to change or repair? I've been using the tractor in warmer weather now and the lift bounce hiccup reset is still there and annoying. I'd like to fix it if it don't involve splitting the tractor or more removing more small parts than I can count.

 

[Soundguy]

are you sure it is the check valve?

are you getting any leakage fromt he cyl mouth? if so.. that's causing the leakdown and regen.

 

[MitchellB]

are you sure it is the check valve?

are you getting any leakage fromt he cyl mouth? if so.. that's causing the leakdown and regen.

No I'm not sure of what or where my leakdown problem is, just the symptom. No oil leakage visible on the outside of the tractor around the lift arms. I've never been into any hydraulic repairs other that to replace the drive
gear & shaft on this pump. Is this cylinder mouth internal? I'm not sure how to check it or the check valve. My limited research so far has mentioned a lot of ball valves and o-rings in this system that appear to be all internal, but I'm not sure what to check first or how. Or if I should even try to do it myself.

 

[Soundguy]

if you havn't looked inside, then you should quit guessing what you need to fix!

I didn't mention any external leaks.

the valve and cyl block is bolted to the underside of the lift cover. a dogbone rides in a cupped piston in the cyl. if the pistol oring leaks, oil passes out the cyl mouth and dumps to sump, making the lift drop, once it drops a bit, linkage regenerates the curcuit by activating the unload valve to deliver more oil to the cyl, then the system unloads and dumps oil to sump when desired height is reached. it will keep leaking an regenerating if you have a leak on the high pressure side.

 

[MitchellB]

if you havn't looked inside, then you should quit guessing what you need to fix!

I didn't mention any external leaks.

the valve and cyl block is bolted to the underside of the lift cover. a dogbone rides in a cupped piston in the cyl. if the pistol oring leaks, oil passes out the cyl mouth and dumps to sump, making the lift drop, once it drops a bit, linkage regenerates the curcuit by activating the unload valve to deliver more oil to the cyl, then the system unloads and dumps oil to sump when desired height is reached. it will keep leaking an regenerating if you have a leak on the high pressure side.

Dang, guessing is all I got at this point, or somebody else guessing before I begin turning bolts. You're right, I'd know more after I looked inside, but I've never opened up the hydraulics on a tractor before, so not even sure as to what I'd be looking at yet. So I hope you understand my confusion and stupid questions (or guessing). You mentioned earlier the check valve holds the load, so my first thought was check valve could be leaking. RPM (2000) and cold temperature (in the 80s) is not the problem now. My thinking was if I thinned my UTF with ATF as you suggested, that would just make the bleed-by worse instead of better wouldn't it if temp was not a problem???? So the internal hydraulic piston does use a rubber o-ring to seal in 861D? (I'm guessing again) that piston o-ring might be the problem? I guess, I need to figure out how to test to see if there is leak-by at the cylinder mouth as you suggested. ??? I guess I might need to wait until I got more time to take this apart. Thanks for the tips and the scolding.

 

[Soundguy]

here is a pdf of the lift cover, look at the upper right, parts 21-30, check valve area at the front of the cover

View attachment HYDRAULIC LIFT COVER & RELATED PARTS, (55_-).pdf



the 861 uses a rubber oring and a leather backup ring on the piston.

with the lift raised and under load you can then look for oil leaking out the cyl mouth.

you can go to the new holland parts site and get an expanded diagram of the valve block cyl and top cover.

a service manual, FO-20 will be helpfull as well.

Official New Holland Online Parts Store and Online Parts Catalog for New Holland and Ford Tractors.

lets see if i can attach this for you, will help you understand the check. PS. din,t mean /not trying to scold. deffinately trying to help

look at parts 21-30 if this pdf attaches