Possible pump failure on Mitsubishi 2050

[MarcusCarr]

pump face

 

[MarcusCarr]

pump face 3

 

[MarcusCarr]

I was using ther term crankcase before...what I meant was the section of the tractor that contains the hydraulic fluid.

Marcus

 

[Soundguy]

Sounds like it could still be a leaky relief valve.. and the higher RPm developed a flow rate fast enough that the relief could not dump it all, thus you were getting some lift out of the system.

Other option is a bypassing pump.. ( I guess it could also be a bad flaw in the spool valve block... )

Soundguy

Here are the results from last night's work on the tractor...and a few pics.

The problem statement is:
at 2000 RPM the implements do not work
at 2500 RPM the implements work very slowly and appear to have full power

Here is what I did.
1. raised the bucket and 3 point as high as it would go.
2. drained the hydraulic fluid in a bucket...fluid looks fine, no froth or discolor
3. gravity dropped the bucket and 3 point. I could hear the oil spraying into the crankcase.
4. disconnected the low pressure suction line from the hydraulic pump and from the crankcase.
5. disconnected the high pressure line from the pump and from the loader valve.
6. removed the hydraulic oil filter...relatively clean...cleaned with compressed air
7. blew air through the low pressure line...there was no obstructions
8. blew air through the high pressue line...there was no obstructions
9. blew air into the loader valve and could hear the last of the oil blowing into the crankcase
10. blew air into the loader valve and operated the 3 point, it lifted. let gravity drop the 3 point and I could hear the oil blowing into the crankcase
11. The air was not enough to lift the weight of the bucket, but I doubt there are obstructions there because the problem statement covers the loader and the 3 point.
12. put everything back together and filled with new hydraulic fluid

Test results:
idle tractor at 2000 RPM, neither the 3 point or loader would operate
raise rpm to 2500, the loader would lift very very slowly and smoothly...same with the 3 point.

I haven't removed the pump yet, but I believe I will be doing that tonight. Unfortunately, I don't know if I would be able to determine a problem if I were to disassemble the pump.

Here are a few pictures...cause we all like pictures =]

Marcus

 

[MarcusCarr]

Can you explain the leaky relief valve theory? Where is this valve and how can I isolate it from the system to verify that the pump is working?

I don't have a hi pressure testing device, nor do I have a trailer to move the tractor.

Sincerely,
Marcus Carr

 

[MarcusCarr]

Well, it turns out that hydraulic pressure gauges are cheap. I will pick on up this afternoon at Napa for 11 bucks. Tonight I will test the pressure direct from the pump.

Does anyone know what kind of pressure I should see at 2000 RPM and 2500 RPM?

Thank you again for your help.

Marcus

 

[rback33]

OK. You guys have had me thinking long and hard on this one. I don't think the sticky relief theory is possible. It either goes over relief or doesn't. You pull it out and check for contamination though. Assuming this relieve DOES exist, I don't think you could have damaged the pump by the deadhead. It should have kicked it over the relief just like when you run out of stroke. I think I am muddying the waters here, even for myself. I still think it IS the pump, but I am doubting the failure was due to the deadhead. If there is not relief in the loader valve or pump though then all bets are off and the deadhead DID do it.... Clear as mud by now I am sure.... IF you can get a flow meter on the pressue line you can see what is getting to the valve.... I don't think you have any flow...

 

[MarcusCarr]

Unfortunately, there is no relief that I am aware of in the pump or the main valve. In a offline conversation, I found the deadheading the pump on these will often either crack the pump housing or expand it in such a way that there is now space between the vanes and the inside of the housing.

Will a pressure gauge connected to the OUT on the pump show me the pump damage or do I need a "flow gauge". I would think that I could measure unrestricted flow by running the OUT into a 5 gallon bucket for some number of seconds to determine GPM.

So I guess I have three questions.

What should the PSI be at 2000 RPM?
What should the PSI be at 2500 RPM?
What should the GPM be at 2000/2500 RPM?

 

[rback33]

PSI should be the same at ANY RPMS
FLOW will vary with the RPM'S, which is why I suggested the flow meter
PM me if you like... I can get you my office number if you want to give me holler...

 

[Soundguy]

Marcus.. you can't just plug the gauge into the pump and fire the engine up.. it will blow the gauge out.

Typically, you chain the lift arms down, and then plumb the gauge into the pressure line, and then operate the lift.. the needle will move to the mas pressure generated.. the relief will kick in at some point and the pressure will go no higher.

To Rback 33... sticky relief valves can and do happen.. they are suposed to be seated and allow no flow to sump unitll their pressure rating is overcome, then they vent pressure and flow to the sump. There will be a limit as to how much flow can be diverted thru the relief.. I would generally think that the relief should be rated for the full flow of the system, for safety. Sometimes the relief does not fully seat.. and some of your oil pressure can be diverted to sump.. giving you less developed pressure and flow.

More than likely, there is damage to the pump and there is internal bypassing taking place now..

Hyd QD's betweent he pump and the relief are such a poor design idea.

Soundguy