Hydraulic Pump

[bazman82]

It's time I tackle the hydraulic pump on my Farmtrac 795dtc. I am not getting the rated psi on my pump (2600). It maxes out at 2000 before dropping back down. I've narrowed the issue down to the pump because it seems like its leaking and I assume its leaking when I hit 2000psi. I can see the hydraulic fluid on the pump around the screws to the in and out pipes that lead to it. With modifications to some allen wrenches I was able to tighten down the 3 screws connecting each pipe to the pump. Then I would test again and to 2100PSI and would hold steady at around 2000. This only worked for awhile because after a days use of the hydraulics I would see the fluid build up again on the screws. The pipes are metal on metal connection to the pump.

Right now, I have a heavy weight hydraulic oil in there and while it does make an improvement when I first start, I lose the pressure when everything heats up. I was thinking the pump is warn out even though its not that old(it actually looked like someone had the pump off at one point because it looks like its been in a vice, marks on the flat side). Less than a 1000 hours on the tractor. Any ideas? I was looking at ordering the pump ($700 shipped) and having it on hand when I take everything apart so that I can just install the new one and be done with it. The other option I was thinking was to pull the pump off, clean everything up the best I can and put the pump back on with new allen screws and some locktight (would have to order). If the second option doesn't fix the solution then I'm back to option 1 with more downtime and doing the work a second time.

 

[RNeumann]

Wow I’d be checking the pressure regulator before I replaced the pump. If the pump couldn’t make pressure because of a leak I’d think it would be dumping a few gallons a minute on the ground......

 

[bazman82]

I've checked the pressure relief valve and made adjustments there. The max I could get it up to and stay steady was 2100. I was able to achieve 2200 but then it would drop below 2000 right after.

The transmission and hydraulics all work off the same tank, open center I believe is what its called (could be wrong). There is a screen in the line between the tank and the pump according to the diagrams. Then it goes from the pump to the rear scv regulator. From there it branches off back to the front of the tractor for the loader scv. I have been testing the relief at the first scv the pump lines go to. Should I try replacing the first scv regulator that the pump line goes into? I priced the parts for the relief valve and well....it would cost more than the new hydraulic pump. Also, why would the screws on the pump have the buildup of hydraulic fluid on them after using. I can try and get some pictures of everything to help make it easier to explain and hopefully using the right terminology as this is definitely not my field of expertise.

 

[RNeumann]

What is the pressure before the relief valve? Does the relief valve require shims or can you simply tighten down the spring? Can you buy just a new spring for the relief valve- I’m thinking that part shouldn’t be too expensive?

 

[oldnslo]

bazman,
Does the hydraulic pump housing get hot quickly compared to the inlet and outlet lines when you are attempting to build pressure? If no the pump is not your problem since a pump leaking close to full flow will get hot very quick. Leaking around the bolts that hold pipes could be O-rings that have hardened and taken a set. These are easily changed if you can get the steel lines lose at both ends.

 

[bazman82]

What is the pressure before the relief valve? Does the relief valve require shims or can you simply tighten down the spring? Can you buy just a new spring for the relief valve- I’m thinking that part shouldn’t be too expensive?

I've only checked the pressure at the rear ports. Not sure if that is considered before the relief valve or not. The valve can be tightened down and loosened and I've achieved different psi pressures doing this. When I tightened it to much the psi wont even reach 2100 psi if I remember correctly from my testing. There was a sweet spot during the testing to get the best usable result and thats what I have it set to now. I would have to try and find the paper that I wrote down the info on for the price on the parts.

 

[bazman82]

bazman,
Does the hydraulic pump housing get hot quickly compared to the inlet and outlet lines when you are attempting to build pressure? If no the pump is not your problem since a pump leaking close to full flow will get hot very quick. Leaking around the bolts that hold pipes could be O-rings that have hardened and taken a set. These are easily changed if you can get the steel lines lose at both ends.

I never felt the housing pump but I do remember that one of the lines off the rear scv was really hot to the touch when in use for awhile. I would have to take a look at that line and see where it is going too or coming from. I will be using the loader tomorrow so I will try to remember to check.

 

[oldnslo]

is the rear scv the valve assembly with the valve you have been adjusting? If yes then I would suspect tank line is getting hot due to a leak path in the valve assembly. Some valves have a power beyond plug with O-rings on them. These O-rings have been known to fail which allows the pressure line to connect to tank like an orifice limiting system pressure.

 

[bazman82]

is the rear scv the valve assembly with the valve you have been adjusting? If yes then I would suspect tank line is getting hot due to a leak path in the valve assembly. Some valves have a power beyond plug with O-rings on them. These O-rings have been known to fail which allows the pressure line to connect to tank like an orifice limiting system pressure.

Correct. The rear scv valve is the one with the valve I have been adjusting.

 

[bazman82]

The blue circle is the line that gets hot and the white circle is where the relief valve is. This is the only picture I have on me atm.

 

[ptsg]

That might be one of the relief valves. There are usually more before that but I'm not familiar with the hydraulic diagram of your tractor.

 

[RNeumann]

I don’t know if that relief valve needs more or less shims to adjust the pressure. But if it is the shim style you will need to add or subtract shims to change the pressure.

Something like this......


BX2200 hydraulic shim installation 10 14 2018 v2 - YouTube

 

[bazman82]

That might be one of the relief valves. There are usually more before that but I'm not familiar with the hydraulic diagram of your tractor.

None before this valve as far as I know. When I follow the line that leaves the pump it comes straight to this unit in the back. From there it goes to the loader controls.

 

[oldnslo]

looks like the line circled in Blue connects to a low pressure hose held on with a hose clamp. If that is true then that is the tank line from that valve assembly.

 

[bazman82]

Well, I'm biting the bullet on this one and taking it to a heavy machinery shop that is within driving distance with the tractor. I am not that confident with messing with the hydraulics and I can't keep the tractor in my shop for an extended period of time either to try and learn my way through it. It isn't all that cheap (110 an hour) but right now I would rather have full use of my hydraulics sooner rather than later and the benefit will outweigh the cost of the repair (hopefully). I'll update on what they find etc etc.

 

[wdchyd]

Might want to call ahead and make sure the repair shop has a flow/test meter setup to properly diagnose your system. Without the proper gauges it will be a guessing game and with the right flow meter they will be able to tell in minutes if and what your pump is putting out for gpm at rated pressures.

 

[bazman82]

Might want to call ahead and make sure the repair shop has a flow/test meter setup to properly diagnose your system. Without the proper gauges it will be a guessing game and with the right flow meter they will be able to tell in minutes if and what your pump is putting out for gpm at rated pressures.

They are a pretty decent size heavy equipment repair shop. I would believe they have a flow meter but I will mention it when I drop it off on Monday. It'll take me about 20 mins to drive the there with the tractor which isn't all that bad. Repair Services | Lacey Heavy Equipment Repair | Western New York

 

[RNeumann]

Thx for the update

 

[bazman82]

So I got an update on this. The repair is saying the pump is no good. They did the pressure test on the line directly from the pump and were only getting readings of max 2400psi at full rpm and then would lose pressure. They then did a flow test on the pump and it failed. $210 for the diagnostic testing. He had 3.16 hours logged but knocked it down to 2 hours which is probably the actually work time they put in on it.

So far so good. I ordered the parts for them since they do a % increase if they order. So my total for parts is $654 (should be there next week sometime). He estimates 3 - 5 hours to replace and 5 hours being if a lot goes wrong. If that stars align and everything is perfect, I may have my tractor by end of the day next Friday. Reality, I'll probably be picking it up sometime the week of the 16th.

I did, however, ask about swapping my loader control valve for one with a 3 third function. He had something coming in today for an excavator that is new to him that he is trying out. Supposedly its a 3rd function control and only cost $295 (part only). He was going to let me know how it worked out for him and if it was something we could do for the tractor. I would like the 3rd function to be at the joystick instead of behind me and to the right.

 

[RNeumann]

It will be interesting to see what he is quoting at nearly $300. Typically folks get an electric over hydraulic valve and then put a switch on the joystick. Some switches are built into the a new joystick handle.