Low Hydraulic Pressure???

[Caseyb1]

Since I began using my new to me 2010 McCormick CT41, aka LS 4010H, I've felt that the loader was weak, it has trouble curling a 6' bucket of horse manure. So I finally put a gauge on it & took a look at the pressure, taking the reading while holding the handle on one of my remote valves. At Idle, 2000 psi.

So, I found the pressure relief and loostened it's locknut and gave it a quarter turn down, the pressure dropped, confirming that I had the right screw, at least in my thinking. So I gave it a quarter turn up from it's original position and the pressure rose, another 1/2 turn or so & I had 2400 psi. Then I raised the engine speed to 1500, the pressure rose. I was under the impression that this would not be the case, that the pressure would remain constant no matter the engine rpm. At 2500 rpm the pressure is about 2600 psi.

The specification in the manual says "Relief Pressure 170~175 kgf/cm @ 30 Liter/Minute" 175 kgf/cm = 2489 psi, if the convertion tool I found is correct.

The main pump is rated at 12cc per rev @ 2600 RPM, so to get 30 liter/Min, you need to be at 2500 rpm, if my calculations are right.

I gave it a short trial and the loader has a lot more curl power. I'll need to adjust it again with the rpm at 2500-2600 before I do any real work with it as I'm pretty sure it's set too high right now.

I'm sure I'm missing something here & invite comments as most of you have much more experience with hydraulic matters than I do. I want to make sure I get this right so I don't end up with a costly repair. At the same time, I don't want the relief set too low so that it's wasting power.

Thank you,

Casey

 

[J_J]

In a perfect hyd system, the pressure would be the same from low to high rpm.

Usually turning down the screw or nut will cause an increase in pressure. Reliefs are set at about a 10 GPM flow rate.

 

[Caseyb1]

In a perfect hyd system, the pressure would be the same from low to high rpm.

Usually turning down the screw or nut will cause an increase in pressure. Reliefs are set at about a 10 GPM flow rate.

So do you think the condition I'm observing is due to a worn pump or ?

Casey

 

[J_J]

It could be a worn pump, or a relief valve, valve spools worn.

The best way to test it is with a 3000 psi pressure gage, a needle valve and a flow control valve. That is what the hyd troubleshooter would use.

If you put a hyd gage in the system, it will at least let you know what you have now so you can do some logical trouble shooting.

If you put the gage in a tee at the IN port of the FEL valve, and you pull the lever for lift, when the lift gets all the way up, the relief valve valve should come on, and then you will read the system max pressure.

When the tractor was new, it had a pump psi rating, if you know that, then that is your baseline for testing.

 

[Caseyb1]

So it would be better to T the pressure gauge into the loader valve instead of deadheading it off the remote? I'll do it, I'm just curious if there is a difference. As for an initial reading, all I have is the relief pressure & safety pressure specifications from the manual, not an actual reading at the time. This tractor is new to me.

Thank you,

Casey

 

[J_J]

For full time monitoring, and trouble shooting, you can install the gage in the IN port or install a male QD in a tee.

The manual should state the pump or operating pressure.

The relief valves are usually set for 50 to 100 psi below pump max pressure.

If the reliefs are set to specs, then the loader and 3pt should operate at the stated loads.

You can also make up one of these to plug into a QD to check the pressure.

 

[Caseyb1]

I have a gauge with a QD on it that I have connected to my remote out. I really don't need a full time install.

The manual states that the relief pressure is 2489PSI with a safety pressure specification of 2845

I believe my pump is shot, since the idle pressure I had before making any adjustments was 2000 psi. It increases with engine rpm, but never gets to the relief pressure from the manual.

 

[J_J]

If you run your engine to max, does the pump make the 2489 psi.

Did you say you tuned down the relief nut and the pressure increased. How much

That 2489 psi, is that for the FEL or the 3pt? When you talk safety valve, that is in the 3pt.

Pressure is dependent on load.

 

[Caseyb1]

To determine safely if I had the right adjustment I turned it down about a 1/8th turn & it dropped a bit. about 150 to 200psi.

Then I went to other way, finally about 3/4 of a turn UP to get the idle pressure to 2450. I'm sure it's set too high right now. When I increased the rpm to 2500 the pressure climbed to 2700 or about there.

The 2489psi specification would need to be for the 3pt, as it is in the tractor manual.

At this point I need to go back & reset it to 2000psi at idle & see what it climbs to at 2500rpm.

I was just under the impression that pressure climbing with rpm indicated a worn pump, is that wrong?

Casey

 

[wdchyd]

The proper way to check pump efficiency is to test pressures with testing the flow rate also....

The pressure without flow does not move the load but rather stall when lifting, theoretically a pump could put out full pressure but with a no flow condition it has o% efficiency.........with 2489 psi and half the rated gpm flow it would still work but have 50% efficiency (meaning pump on the way out junk)....in a perfect world you'd like to see 80-90% efficiency for a normal hyd system......not easy to determine without testing flow also

I have somewhere on here a video but am having trouble linking it to the vid using a flow/load meter......it shows how the pressure guages and flow meter helps in diagnosing/ruling out pump troubles....