Case CX-47 Hydraulic Issues

[Lotsaprojects]

Hello All,


I’ve got a 2004 case cx47, it’s always been a great machine but recently started getting a little weak when hot. Ran through the pressure checks in the shop manual, and have found (a) issue…

The piston pump has two outlets, they both come into the control valve next to each other, and our are both governed by a single main pressure relief valve. There is a corresponding test port for each of the two pump inlets. One of the pump is dead on spec, 3700 pounds if I recall correctly. The other however, is only indicating at 2000 pounds.

Certainly it cannot be the main pressure relief valve, as neither side would build the 3700 pounds if it was dumping off at 2000 pounds.

Pilot pressure is spot on at 500 psi, and so apart from some kind of internal leakage in the section of the control valve supplied by the underperforming half of the piston pump, I’m kind of at a loss.

I did swap the two piston pump inlets into the control valve, and the problem did not follow the swapped input line, it remains within the same section of the control valve.

Any thoughts or suggestions on what to look for next? Thank you in advance.

 

[Kobe Steel]

I do not have any shop manual on these machines but if you had swapped the main pump lines and the issue did not swap over then I would think it is one of the main relief valves and I would assume it has 2 main relief valves for the piston pump circuits P1 and P2 , one main relief for the gear pump circuit P3 and one main relief for the pilot gear pump circuit P4

Best regards

 

[Lotsaprojects]

It seemed to me that the main relief valve for the axial pump regulated both inputs P1 and P2. I checked the manual and it seems to agree that the one relief valve protects both axial pump inputs…

At this point I have to think there’s some internal leakage in the valve body, tricking the pump out of throwing more swashplate into it

 

[laidback01]

runs good when it's cold, poorly when hot? increase in the viscosity of the hydraulic oil will solve that. 2004, you are out of warranty... the pump(s) or some part is wearing, so, why not just get more time by moving up a grade or two in viscosity?

the makers never recommend it - when the machine is new, as it could be a problem. might be other reasons too. so... take this idea with a grain of salt. I can say I've done this to a couple kubota and deere tractors and my 410b (1983) backhoe. the backhoe is min personally, and it used that JD Hygard Summer/Winter oil. I don't know what viscosity it is, but when it warmed up, that machine would let the boom drift down if you let go of the controls. the front bucket would tilt because the valve body is ... old. Switching to AW46 almost fixed it, so now I buy aw46 and aw68 at my local tractor shop and do a 50/50 for the old girl. it's fine. Has power galore.

 

[Lotsaprojects]

That’s true, and I’ve done that on several machines with decent luck depending on what the root cause is. I even bumped up the viscosity on this machine a few years ago but it’s not enough to make much of a difference. We’re almost 2000 psi low on one of the two axial pump outputs to the DCV. I’m afraid this suspected internal leakage is simply too large to overcome by any means other than actually fixing it.

 

[laidback01]

yeah, there's a limit to every fix, professional or not. Good to do it the right way after the other way has given you a bit of time.