Allis 5040 slow Hydraulics

[ametcalf]

The 3 pt lift has been slow on our Allis for several years. I have had it to two different shops for other work and told both shops to fix it if they could. Neither shop did anything to improve the lift. I told my wife the other day that I was going to get a gauge and maybe with the help available here I can find out the problem and fix it myself.
I put a 5000# gauge on one of the remotes and this is what I got.
Idle 100 psi
1000 rpm 200 psi
1500 rpm 500 psi
2000 rpm 800 psi
2400 rpm 1000 psi
The manual says that the pump should put out 6.3 GPM at 2600 rpm and 2133 psi. I don't have an easy way to check the flow but it seems to me that what I need is a new hydraulic pump. I think I can get one online for $283 and plan to go ahead unless some one has a better idea.
Any and all advice is appreciated.
Thanks, A. Metcalf

 

[ametcalf]

The 3 pt lift has been slow on our Allis for several years. I have had it to two different shops for other work and told both shops to fix it if they could. Neither shop did anything to improve the lift. I told my wife the other day that I was going to get a gauge and maybe with the help available here I can find out the problem and fix it myself.
I put a 5000# gauge on one of the remotes and this is what I got.
Idle 100 psi
1000 rpm 200 psi
1500 rpm 500 psi
2000 rpm 800 psi
2400 rpm 1000 psi
The manual says that the pump should put out 6.3 GPM at 2600 rpm and 2133 psi. I don't have an easy way to check the flow but it seems to me that what I need is a new hydraulic pump. I think I can get one online for $283 and plan to go ahead unless some one has a better idea.
Any and all advice is appreciated.
Thanks, A. Metcalf

I copied this from a response J_J gave to someone who was having a hydraulic problem and I think it is good advice for my situation.

"Pump could be weak and not pumping the potential pressure.
The 3pt valve could be leaking.
Piston seals worn.
The relief valve could have some trash in it.
The safety valve might have some trash in it.

Does the 3pt try and leak down after the lift is raised?"

In my case the 3pt does not leak down. I think the problem is either with the relief valve or the pump. I don't see any way to tap into the hard line that goes from the pump to the hydraulic control valve under the seat where the relief valve is so I can put a pressure gauge on it.
I am not sure but I think my problem is either in the relief valve or the pump. Is there a way that I can tell which it is or do I just change one and if that doesn't help, change the other?

 

[Leejohn]

How did you hook onto your remote? Did you just plug it in? Do you have a loader? By your reading you are not dead heading to get the relief valve to open.

 

[ametcalf]

How did you hook onto your remote? Did you just plug it in? Do you have a loader? By your reading you are not dead heading to get the relief valve to open.

I appreciate your response, not only are the hydraulics weak on our tractor but hydraulic knowledge is weak in my head.

I use the up side of the remote to raise the lift on a dump wagon that I have. I put a male quick disconnect on a gauge and plugged it into that side of the remote and raised the lever as if I were trying to dump the wagon.

 

[MHarryE]

Based on the numbers it really looks like 1 of 2 of J J's items is your problem. The problem is likely to be either a bad relief or badly worn pump. Do you have any idea how to get to the relief valve on your tractor to check it out? This is where having a service manual really comes in handy. Have you changed your hydraulic oil and filter? If you have and if you still have the filter, it would be interesting to open the filter and check for material. I assume your pump is a gear pump with aluminum housing - if the pump is badly worn you will find aluminum housing particles in the filter media.

 

[Leejohn]

MHarryE is right. Find your main relief if you have one, if not it's in the 3pt valve or may be the rockshaft housing.

 

[ametcalf]

Based on the numbers it really looks like 1 of 2 of J J's items is your problem. The problem is likely to be either a bad relief or badly worn pump. Do you have any idea how to get to the relief valve on your tractor to check it out? This is where having a service manual really comes in handy. Have you changed your hydraulic oil and filter? If you have and if you still have the filter, it would be interesting to open the filter and check for material. I assume your pump is a gear pump with aluminum housing - if the pump is badly worn you will find aluminum housing particles in the filter media.

I have the operator's manual and the service manual and the relief valve is real easy to get to. I just don't know what I should be looking for when I take it apart. The filter is a metal screen type of filter and over the years I have changed fluid and cleaned the filter as well as having a shop change the fluid. I assumed that when they changed the fluid that they also checked the screen. I don't remember seeing great amounts of metal in the screen but I don't know about what the shop may have found. Communications is not their strong suit. The tractor is at least 30 years old and as far as I know the pump nor the relief valve have never been changed. I can't remember how many hours it had on it when I had the engine overhauled quite some time ago. When they overhauled the engine I had them put a fix tach and in now reads 3600 hours so my guess is the pump and relief valve have at least 5 or 6 thousand hours. I didn't know that the pumps had aluminum housings. With that in mind my guess is that there has been alot of wear with that many hours and the tractor probably deserves a new pump. I think I will pull the relief valve when I get a chance and see if there is anything obvious. If anyone has any suggestions of what I should be looking for I would appreciate their wisdom.
Thanks

 

[MHarryE]

Some relief valves can get a bit complicated but it is likely that on your tractor it is a direct acting relief which means a spring is acting on a poppet. Hydraulic pressure pushes on the poppet until it overcomes the spring pressure. The poppet will lift off its seat allowing oil to flow directly back to tank. If it is this type of relief, it can be as easy as disassembly and inspection to make sure nothing is caught in the relief and there is no wear on the seating surfaces. Then the trick is to get everything reassembled correctly and to the right pressure setting. You have a pressure gauge - the gauge and wrenches should be all you need to set the relief if you disassemble it, find a problem, and solve it. When I talked about cutting open a filter and checking the media for wear particles, I had in mind a spin-on type filter element with a pleated fiber media. With just a strainer, its not possible unless you find big chunks. If the oil is changed properly, it is warmed up and drained so all of the wear particles will be in suspension and go out in the drain bucket. I worked in Engineering for Allis-Chalmers from 1967 - 1989 but on combines. We used Cessna hydraulic pumps exclusively but I do not know if tractors also used Cessna. The Cessna gear pumps were a simple and robust pump but at 5,000+ hours with only a strainer for filtration, I would not be surprised to find the pump worn out. We used a paper filter on combines but even then we didn't figure on even a 5,000 hour life for our gear pumps.

 

[ametcalf]

MHarryE,
Thank you very much, you have been very helpful. This tractor was made in Romania so I am not sure where the hydraulic pump was made. If I am understanding the manual right, there is no adjustment for the relief valve. If it is out of specs you replace it. Here is what the trouble shooting section of the manual says:

"E. Poor lifting capacity, less than estimated. 1)Probable cause--Wrong pressure relief valve setting. Remedy--Replace it. 2)Probable cause--Low pump efficiency (normally accompanied by a considerable increase of the lifting time). Remedy--Test pump performance and overhaul it, if necessary.

My thinking now is that I will take out the relief valve and look it over and if there is nothing obvious that I can see I will put it back and replace the pump and see if that helps. I will let you know what happens.
Thanks again.
A Metcalf

 

[MHarryE]

I hadn't realized this is a tractor sourced in Romania until you mentioned it. Definitely not a Cessna, nor any other US built pump. I did find this comment from another person who owns a 5040:

Mine runs great and everything works however, I am having troubles finding parts (relief valve, fender, front grill). Does anyone have a good site for parts? v/r Marty

Interesting that this person is looking for a relief valve. Not sure if that indicates a common problem.

The statement you have from the service manual indicates a cartridge relief that is not adjustable and cannot be disassembled to clean and inspect, but you might be able to spot something unusual like a cracked part or piece of metal stuck in the valve. I'm a bit confused by the "overhaul" comment in the service manual. If it is a gear pump like I suspect, the solution is the one you mention - replace. That's what the major gear pump manufacturers I have worked with over the past 20 years, Bosch-Rexroth and Sauer-Danfoss have said. Pump output not up to specs, replace the pump.