Case CX14 low/no hydraulic power

[blankey85]

Hello all, I'm in need of some help from the experts on this forum. My brother has a 2004ish? Case CX 14 mini which has sat pretty much unused over the winter and when he went to use it the other day it has barely any hydraulic power. We have a repair manual, but I'm not very familiar with hydraulic systems, so here I am looking for help.

The bucket will uncurl a very minimal amount and the house will try to rotate, but that seems to be about the extent of what it will try to do. The arms/blade/tracks don't seem to do anything. Since some operations will move a little I don't believe it to be the locking switch in the arm rests.

I've checked the strainer filter and it wasn't clogged and there didn't seem to be any debris in the hydraulic tank. Pilot valve tested and was right at the 500 psi called for.

I've going to check the other pressures at the main control valve. Is there anything else I should check or test before that? I'm at a real loss as to how it worked fine in the fall/early winter and now doesn't really do anything.

Thanks in advance for any help!

 

[blankey85]

So I was able to spend more time on the excavator this weekend. I'm still at a loss of what's wrong with it. I checked the voltage at the two solenoids at the pilot control valves. Both get 12 volts and click with the level locks engaged. Removed the relief valve at the pilot valves and it doesn't appear clogged and turned the set screw down and then turned it back up to 500 psi with no problems.

I've followed the Hydraulic and Electrical troubleshooting flow chart and get the whole way through where it points to the other system. Still have no more function than before I started looking at it and still lost.

 

[whallbuilding]

Hi. I have a cx16b. same problem as yourself. of the pump I have 500 psi on the pilot pump but on the main pump I only have 150 psi on both lines. We have flow but no pressure I disconnected everything and put a valve on each of the output lines running back to the tank and then closed the valves, still no pressure.
I have changed the internal parts of the pump (Nachi axial piston pump) guess what, still the same grrrr.
done the same as you with the relief valves at the two solenoids.
sorry Im not helping you but if you found a solution I'd Like to Know please.
mine worked fine for then one morning just dead.
thanks

 

[blankey85]

Sadly we haven't gotten this resolved. A mechanic down the street was supposed to be coming to look at it, but hasn't ever showed up yet. I'm curious, since you've had the pump out, what is the connection between the pump and motor (i.e. splined shaft with a key, a coupler, etc.)? I've asked a bunch of different people about this issue and have gotten responses all over the board...air in the lines, connection between motor and pump, pump is bad, relief valve stuck open, pistons in the pump stuck, ect. I have a flow meter with a loading valve and put it in the line between the pump output and the control valve. It shows about 1 gpm (idle or full throttle) and if you use a control it pretty much bottoms out and the pressure doesn't raise.

I'm not 100% sure as to what I'm looking for when using the flow meter or what the flows/pressures should be and when.

The left track turns very slowly, the arm and slew work a tiny bit. That's about all the function I have.

Sorry I'm of no help to you either, but maybe someone can chime in.

 

[whallbuilding]

We removed the pilot pump from the end of the main pump which is driven by a splined shaft. then we remove the end off the pump, then you can remove the block with the Pistons and swash plate. These slide onto the same shaft as before which is connected through to the bell housing.
Only 2 studs hold the pump to the bell housing but we haven't got them undone as they are extremely tight and cannot get an Allen key on them good enough.
We thought it was a blocked strain filter to start with, but that wasn't it.
Then we checked for air getting in to the inlet hose, re sealed everything but still no joy.
We don't have a flow meter, but when we disconnected the outlet pipe from the valve block and ran it the flow looked plenty.
Hope fully someone can help.
Thanks

 

[lantraxco]

I am not familiar with this system but it sounds like the pump is not coming on stroke. Is there a small hose or possibly two coming back to the pump from the main valve bank, or some electrical wires? Pictures would help.

If your charge pressure holds when trying to use other functions then it's likely the pump drive is okay, as it seems the pilot pump mounts on the back of the main pump?

 

[blankey85]

I believe there are only 4 lines to/from the pump and no electrical wires. There is the suction line from the tank, pilot output line and 2 main lines. I want to say there is an internal pilot passage in the pump (there are 2 dashed lines in the schematic from the P3 (pilot) to the P1 & P2 lines).

I have hydraulic schematics in PDF that I could send or post if that would help.

 

[lantraxco]

Don't think you can post a PDF, if you can convert to GIF or JPEG that will work (I use PAINT). I will PM you my email addy also.

If it's a piston pump with swash plate, something has to cause the swash plate to change angle, usually a feedback line controls it, or the compensator/regulator spool holds it at a specific pressure or pressure drop past an internal orifice. Like I said I don't know these particular machines or pumps, but it's gotta be in that control if you have very little flow and no pressure.

 

[whallbuilding]

Hi on mine it is a Nachi piston pump. No wires. One large inlet pipe. One (p1) off the pilot pump (500psi). And then two (p2 & p3) of the main pump. There is a large spring inside pushing the swash plate back but I can't understand what make the swash plate change angle.
My pump is noisy. Like a bag of marbles. Which everybody says air is getting in. The inlet pipe is good and the the filter. I have had the bleed plug undone on top of the pump to let air out. Could air get in elsewhere? No oil is leaking out of the pump.
Thanks again.

 

[blankey85]

lantraxco I sent you an email.

From the shop manual mine appears to have the same pump or at least the same style. It doesn't make any noise, unless you are trying to use some function. I didn't know their was a bleed plug.

 

[lantraxco]

Well, the schematic is interesting to say the least, but not really unusual. Thought I would reply on here in case anyone else has this problem now or in the future. It appears to me to be a fairly simple system, closed center and pressure compensated. What that means is all the control valves are closed off in neutral so no oil from the pump flows to tank and the pump maintains a constant high pressure. I didn't see a pump pressure spec in the schematic but the reliefs are roughly 3,000 psi so it will be a bit less than that. As you move a control the associated valve spool shifts and opens up the pump supply passage to whatever cylinder or motor, as the oil pressure drops on the supply side the pump compensator shifts the swash plate to pump more oil, always trying to maintain the set pressure.

You both have good pilot pressure, so we can assume I think that the pump is actually turning as long as the pilot pressure does't drop off at some point in testing. The two solenoid valves are not really part of the problem I don't think, one is for the two speed travel signal, the other supplies pilot oil to the joysticks and a small lock cylinder that locks and unlocks the mechanical linkage controls, this is the safety system.

So, with what we know so far you shouldn't have more than a tiny bit of flow on either pump line with everything in neutral, but you should have I would think at least 2,500 psi on both pump lines.

Anything in the manual pertaining to the pump and regulator operation, or adjusting?

 

[blankey85]

When I put the flowmeter in the P2 (I believe, or could have been P3) there was very little flow but no pressure. If I understand you correctly there should have been about 2,500 psi?

 

[lantraxco]

Well, I missed one single connection in the valve block schematic and led you astray. The manual clearly states the pump flow returns to tank in neutral.

When all controls are in neutral there is pump flow through that single point straight through to tank at low pressure. So, to correct myself, sorry, there should be 4GPM at high idle from each line, P1 and P2, at very low pressure until you actuate a control. With your flow meter inline, you should see 4GPM and then as you close off the load valve (don't close it too far, keep the pressure under 3,000 psi or something may blow up) you should see pressure increase and flow drop off.

This pump is a very clever bone simple setup, it has six pistons and a porting setup that ports half the pistons to P1 and the other half to P2 with a common suction, an eloquent way to use one pump and divide the flow exactly in half. The flow regulator is also bone simple, the spring holds the swash plate at maximum angle and as pressure rises the resistance from the pumping pistons under pressure pushes the opposite side of the swash plate back against the spring until the forces balance.

If you're not getting flow there's an issue with the suction or the rotating group or valve plate, or possibly a broken regulator spring?

 

[blankey85]

That makes a little more sense. So with the flow meter in line, it measured about 1 GPM at low or high throttle. I closed the load valve a few turns but the pressure didn't move, but I was hesitant to turn it too far.

When you say maximum angle is that more perpendicular to the shaft or less perpendicular? Just trying to understand how this thing works.

We did pull the suction line from the tank and the filter didn't look like it had any debris so I don't think that is the issue. How do I check the valve plate or a broken regulator spring?

Thanks again for all the help!

 

[lantraxco]

When the swash plate is perpendicular to the shaft, the piston feet run flat as they go around the circle and the pistons basically don't move in or out at all, so no oil is pumped. The way they show it with the spring at the top, the further out the top of the swash plate is, the more angle, the further out and in the pistons move the more oil is pumped per revolution. You can see a pin and spacer washers behind the swash plate opposite the spring, that's the stop for maximum angle/displacement. They don't really show it but there's a pin on either side of the swash plate dead center with the shaft that the plate pivots on.

In order to check the internals you have to pull the rear cover off, if it was me I would probably try to pull the pump, if the two bolts that hold it are dificult you can unbolt the big round adapter plate from the flywheel housing, the pump should be splined and slip right out of the drive. Good chance to inspect that drive on the off chance we're chasing ghosts and the problem is actually bad splines or something though I don't think so.

If you pull the pump set it so the back cover is up, or if you do it still in the machine, either way pull the four big bolts by loosening them a bit at a time kind of equally so the cover comes up level, should be spring tension there. Look for obvious damage, anything that's broken or sheared, or anything that rotates that looks like it's been scored or smeared somehow. The valve plate I think locates on a roll pin, see if that's sheared. You might need a new gasket to reassemble.

 

[blankey85]

So I've finally gotten a chance to pull the pump and I've taken it apart. I see absolutely nothing that resembles damage/scoring to the internals of the pump and the splines look perfect. I took some photos and uploaded to photobucket, there are more than these two, but I'm struggling with getting them to post.






I can't find any section in the service manual about the coupler, although it doesn't look like that I thought it would. In the parts manual it labels it as a Power Take-off. The parts diagram is uploaded with the pictures. It shows a pin which I guess could be sheared off but I don't seem to understand what the pin does with all the bolts shown.

Let me know if you see anything in the photos that I overlooked or if there is something else to check into.

Thanks.

 

[lantraxco]

That's fine we can scroll to the rest once we get to the photobucket site.

Looks to me like you're missing a part, it's #4, Ball Guide, it splines onto the shaft and those three pins push it, and the set plate which holds the piston feet, up against the swash plate, and that pushes the cylinder back against the valve plate.

Generic parts pictures:

 

[blankey85]

I have that part and the spline in it look fine too. Just didn't get a photo of it, but it looks identical to the piece in the bottom photo you added.

 

[lantraxco]

Was it setting on top of those three pins, with the set plate (retainer plate, weight plate, #6) fitted to the ball side?

After looking over your pictures more closely, the piston slipper feet are shot, all beat up on the outside, and I think the swash plate is toast also from the discoloration. Something ain't right in there, can't tell if something failed or it was run short of oil or with a plugged suction. Are the three pins in the cylinder the same length, and the same height above the cylinder nose?

Where did the extra pin come from that's laying next to the brass valve plate?

Here's a picture of similar Nachi pistons, notice how thick they are and that the center is depressed inside the outer ring?

 

[blankey85]

If those are what the pistons look like new, than I'm sure they are just about wore out. Photobucket is blocked at work and I some how blew up my phone last night, but I'll look closer and take some new photos tonight of the pistons and the swash plate.

I lined up the 3 pins and they all looked to be the same height, but I will check tonight with the micrometer their length and how much they stick out. There are only 3 pins, so it must have gotten moved between photos.

I'm pretty sure it hasn't been run short of oil since we've had it and we've checked the suction line, but we will check it again before it's all put back together.