722 Hydraulics

[Atilathehun99]

I was plowing the drive yesterday and noticed they hydraulics getting weak. At first I didn't think much of it as they've always been slow in cold weather. Finally it essentially quit responding; no hoist, no bucket curl, no drive motors. I checked the hydraulic oil as it does have a leaky wheel seal. It took about 9 quarts to bring the level up to drip from the fill check plug. Today I went out to see if that did the trick and nothing. Little to almost no response from the hydraulic system. It will move a little bit, the hoist will raise a little bit and a little bucket curl. The unit is equipped with a petcock on the hydraulic line near the radiator. This was put in to bleed air from the system. Currently when the valve is open I get neither hydraulic fluid nor air. Do you think the main pump is shot perhaps due to running it with low fluid level?

 

[antfarmer2]

Are you sure your not filling the gear case instead of the resevoir

 

[Atilathehun99]

Are you sure your not filling the gear case instead of the resevoir

Pretty sure I'm correct. I'm filling at the same point I've done it the past to top it off or when I've changed the hydraulic fluid. Using 10W-40 just like the manual calls for.

 

[OldMachinist]

Pretty sure I'm correct. I'm filling at the same point I've done it the past to top it off or when I've changed the hydraulic fluid. Using 10W-40 just like the manual calls for.

If you loosen the drain plug does anything comes out. You may have some water in the oil tank that froze and blocked the pick up.

 

[Atilathehun99]

If you loosen the drain plug does anything comes out. You may have some water in the oil tank that froze and blocked the pick up.

Haven't done that yet. I had to refresh my memory where the drain plugs were. Seeing they're behind the back wheels it looks like I'll have to pull them to do the check. On a similar note I'm guessing the hydraulic oil never looks clear. I've always seen this oil (before and after changes) to be a bit milky. I would expect that some of that could be water but most (?) is probably just entrained air?

 

[OldMachinist]

Haven't done that yet. I had to refresh my memory where the drain plugs were. Seeing they're behind the back wheels it looks like I'll have to pull them to do the check. On a similar note I'm guessing the hydraulic oil never looks clear. I've always seen this oil (before and after changes) to be a bit milky. I would expect that some of that could be water but most (?) is probably just entrained air?

It shouldn't have air in it unless you have a suction leak. Likely its water and it doesn't take that much to freeze up a hydraulic system. Normally the filters freeze blocking the flow but on the older machines with oil tanks on the sides it sometimes gets enough in them to block the pump suction.

 

[Atilathehun99]

It shouldn't have air in it unless you have a suction leak. Likely its water and it doesn't take that much to freeze up a hydraulic system. Normally the filters freeze blocking the flow but on the older machines with oil tanks on the sides it sometimes gets enough in them to block the pump suction.

Do you have an idea how far off bottom the pump intake is? Another thing is that before I lost hydro power I had been running the machine for probably at least 20 minutes. I suppose under the ice block scenario it could have been running OK and after warming a bit a piece of ice could have loosened and moved to block the intake. Again I'm worried (and wonder about) the possibility that running the system 10-quarts low could have trashed the pump. I think it's a 28 quart system so I don't know if running at 2/3 capacity would be low enough to cause damage. P.S. After starting things up after topping off the system the FILT light stayed on for several minutes. Thanks for you help.

 

[OldMachinist]

Do you have an idea how far off bottom the pump intake is? Another thing is that before I lost hydro power I had been running the machine for probably at least 20 minutes. I suppose under the ice block scenario it could have been running OK and after warming a bit a piece of ice could have loosened and moved to block the intake. Again I'm worried (and wonder about) the possibility that running the system 10-quarts low could have trashed the pump. I think it's a 28 quart system so I don't know if running at 2/3 capacity would be low enough to cause damage. P.S. After starting things up after topping off the system the FILT light stayed on for several minutes. Thanks for you help.

Another thing I just saw in the service manual is that the pump in this model can loose prime if the fluid level get too low.

 

[Atilathehun99]

Another thing I just saw in the service manual is that the pump in this model can loose prime if the fluid level get too low.

O-machinist I truly appreciate your responses. They are very helpful. After what you've said I'm hopeful that I've just lost prime. I've located the reservoir vents; haven't touched them yet. They will be hard to access. They appear to be some sort of plug-in vent made of rubber. Do I plug them for the prime by sticking in a rubber plug or do you think the vents are threaded? I'm also considering topping of with 10W -30 instead of 10-40.

 

[ChandlerW]

O-machinist I truly appreciate your responses. They are very helpful. After what you've said I'm hopeful that I've just lost prime. I've located the reservoir vents; haven't touched them yet. They will be hard to access. They appear to be some sort of plug-in vent made of rubber. Do I plug them for the prime by sticking in a rubber plug or do you think the vents are threaded? I'm also considering topping of with 10W -30 instead of 10-40.

Hey Atilathehun I have a 722 that I'm working on too. If you want to hit me up at [email protected] I'd like to compare some notes with you.

 

[Atilathehun99]

Another thing I just saw in the service manual is that the pump in this model can loose prime if the fluid level get too low.

OldMachinist I can't express my gratitude for your suggestion. I did the prime per procedure and it worked. On another note some time I've been considering an upgrade. My needs are snow plowing and the occasion need for light excavation and hauling around the homestead. I ran into a local Bobcat salesmen the other day and he mentioned that they would be taking in an S130. It's a farm owned unit but it has a ton of hours....+/- 7000. We didn't get down deep on pricing but he thought it would be in the $7K range. With my need I probably rack up less than 100/yr. Any thoughts from anybody?