41b Hydraulic issues

[futuresweets10]

I got a cat 416b backhoe and it had no hydraulic pump when I acquired it. (pump went out on previous owner). I purchased a new pump (aftermarket) and installed it...
I took the return line off the tank and bumped the ignition over a few times to help get the fluid started, then cranked it up. It took a second but fluid started flowing from the return line. I then turned the machine off and re-connected the line to the return of the tank. I got back on the machine and started to try the hydraulics out.

-The steering works great with no problem
-The outriggers go down and up with no problem, but once they hit the ground wont lift the weight of the machine
-The front arm will come down, but has to be worked ALOT to get up
-The front buket will not tilt at all (all the way down at the moment
-the back swing seems to work fine
-the back arm works on one cylinder but not the other
-the back bucket seems to move ok.

All of the hydraulics that dont move or move slowly can be pushed manually (someone holding the control and someone pushing on the bucket or arm)

At first I figured it was air in the lines, but now I dont know. With some of them, playing with them seems to make them work somewhat, but others it dosent help. its almost like the pump is working, but the pressure isnt high enough. Any adjustment on the pump pressure wise? Any other ideas? Thanks guys.

 

[futuresweets10]

Nobody has any insight???

 

[wdchyd]

When you installed the pump did you fill the case drain???? :confused2:

Did you clean tank and change filters?

There is adjustments on that pump (2 stage pressure compensator mounted on back plate)...I don't recommend adjusting without pressure guages and flow meter/load valve to monitor pressure and flow while running a simulated load and running the machine....

If I'm not mistaken from a previous thread that you started, you've inherited someone elses troubles....just throwing on a new/rebuilt/used pump is not a cure all....these piston pumps are not as easy a DIY if new to hydraulic troubleshooting....yes the pump could have been bad but the new/rebuilt one needs to have adjustments made to it to avoid same problems resurfacing....or worse crashing the replacement pump again....

Maybe you need hands on help from someone locally that is familiar with this machine and has proper technical specs to adjust/test this pump.....much better "Insight" Yes?

 

[futuresweets10]

When you installed the pump did you fill the case drain???? :confused2:

Did you clean tank and change filters?

There is adjustments on that pump (2 stage pressure compensator mounted on back plate)...I don't recommend adjusting without pressure guages and flow meter/load valve to monitor pressure and flow while running a simulated load and running the machine....

If I'm not mistaken from a previous thread that you started, you've inherited someone elses troubles....just throwing on a new/rebuilt/used pump is not a cure all....these piston pumps are not as easy a DIY if new to hydraulic troubleshooting....yes the pump could have been bad but the new/rebuilt one needs to have adjustments made to it to avoid same problems resurfacing....or worse crashing the replacement pump again....

Maybe you need hands on help from someone locally that is familiar with this machine and has proper technical specs to adjust/test this pump.....much better "Insight" Yes?

Pretty much the type of answer I was looking for, but not what I wanted to hear..... Yes, I inherited someone else's troubles. The old pump was decentigrated, so I know it was bad. I would love to find someone who I can pay to adjust the pump, but cant seem to find ANYONE. I am capable of adjusting it myself If I had the tools and knew the basics, but I dont know the basics. I know I need a pressure gauge and assume I need to hook it to the service port thats on the pump's pressure line, but have no clue about the "flow meter/load valve" you speak of.

BTW, I did fill the case drain, but it also has a line running from the case drain to the bottom on the tank that fills it from the tank. I also cleaned the tank (looked like brand new) and replaced the filters

 

[J_J]

Have you put a gage in the system to see if things are working? Install a hyd gage in the input hose on the first valve in the system after the pump. With all valves in neutral, should read little or no pressure. If a lever is activated, and all connections are good, then you should see high pressure. . If you have QD's, recheck the connection. Do you have to tie a lever back to get hyd to the back? Is your return hose from the BH connected properly? Did anybody mess with the relief valves?

 

[futuresweets10]

Have you put a gage in the system to see if things are working? Install a hyd gage in the input hose on the first valve in the system after the pump. With all valves in neutral, should read little or no pressure. If a lever is activated, and all connections are good, then you should see high pressure. . If you have QD's, recheck the connection. Do you have to tie a lever back to get hyd to the back? Is your return hose from the BH connected properly? Did anybody mess with the relief valves?

I have not hooked up a gauge yet, because I cant seem to locate one to purchase. There is a service port on pressure line right past the pump, would this port work the same as hooking it up where you described?

Ill be honest, Im kinda lost with your post, but im trying to follow it (my fault, not yours). I am fairly green when it comes to this stuff. If by QD's you mean quick disconnects, there are none. Also, what do you mean by tie a lever back to get hyd to the back? I do know that after the machine broke the previous owner had to loosen some of the lines to be able to get the implements up so it could be moved and worked on. (I assume only the lines going to the cylinders). The whole relief valve thing is new to me... Where would the relief valves be?

Bottom line..... All hoses should be hooked up properly and none of that should have been messed with. I am to "green" to know where or what relief valves are so I need a little schooling on that. I am going to try and find a pressure gauge today and try that.

 

[AKKAMAAN]

Nobody has any insight???

You have a variable displacement piston pump (axial). They are used on Constant pressure systems, usually with a feature called Unloaded. That means that pump drops to a lower stand+by pressure when there is no demand on flow. That demand usually comes from the directional valve, as a "signal" in a 1/4" hose.
There is a pressure compensator on the pump, looks like a smaller housing with one or two adjustable valves. Two valves, if this pump is made for this Constant Pressure Unloaded (with stand-by pressure). This mentioned 1/4" hose, from the control valve should be connected to the compensator. If not, pump will still deliver flow, but only a very low pressure, typically adjusted to some where between 300-600psi. This pressure is set by a spring. This is the stand-by pressure.
This stand-by pressure is enough to make cylinders move with no load, like swing and bucket curl etc...

The signal to the compensator, will add pressure (force) on the valve poppet, so total pump pressure will be stand-by plus system pressure. System pressure is set by a relief valve in the control valve.

If, eventually, your system is a Load Sensing system, it will work the same way as the Constant Pressure system, except that the pressure signal from the valve will be equal to the highest load pressure that for the moment is actuated by the control valve......

This is pretty complicated stuff if you have zero experience, but lets take everything from scratch. We need more info to be able to help.

Take some detailed photos on the pump, pressure compensator, control valve and the plumbing, and post.
Read the manual to determine what type of hydraulic system you have....if there are any schematics on the system available, please scan or take photo pix on them and post too.

 

[futuresweets10]

You have a variable displacement piston pump (axial). They are used on Constant pressure systems, usually with a feature called Unloaded. That means that pump drops to a lower stand+by pressure when there is no demand on flow. That demand usually comes from the directional valve, as a "signal" in a 1/4" hose.
There is a pressure compensator on the pump, looks like a smaller housing with one or two adjustable valves. Two valves, if this pump is made for this Constant Pressure Unloaded (with stand-by pressure). This mentioned 1/4" hose, from the control valve should be connected to the compensator. If not, pump will still deliver flow, but only a very low pressure, typically adjusted to some where between 300-600psi. This pressure is set by a spring. This is the stand-by pressure.
This stand-by pressure is enough to make cylinders move with no load, like swing and bucket curl etc...

The signal to the compensator, will add pressure (force) on the valve poppet, so total pump pressure will be stand-by plus system pressure. System pressure is set by a relief valve in the control valve.

If, eventually, your system is a Load Sensing system, it will work the same way as the Constant Pressure system, except that the pressure signal from the valve will be equal to the highest load pressure that for the moment is actuated by the control valve......

This is pretty complicated stuff if you have zero experience, but lets take everything from scratch. We need more info to be able to help.

Take some detailed photos on the pump, pressure compensator, control valve and the plumbing, and post.
Read the manual to determine what type of hydraulic system you have....if there are any schematics on the system available, please scan or take photo pix on them and post too.

There is a 1/4in hose that runs to the pump (on top) and the rest of the lines connect on the back. The other end of the 1/4in hose connects somewhere under the machine (to the one of the valve assemblys I assume?)

The two valves you speak of are on the back of the pump and not where the 1/4line goes in.
I am an auto tech by trade and have NEVER found anything that I couldn't figure out, so I know I am capable of doing this if I am pointed in the right direction. You seem to know your stuff, I look foward to hearing back from you and will get pics up ASAP

 

[AKKAMAAN]

There is a 1/4in hose that runs to the pump (on top) and the rest of the lines connect on the back. The other end of the 1/4in hose connects somewhere under the machine (to the one of the valve assemblys I assume?)

The two valves you speak of are on the back of the pump and not where the 1/4line goes in.
I am an auto tech by trade and have NEVER found anything that I couldn't figure out, so I know I am capable of doing this if I am pointed in the right direction. You seem to know your stuff, I look foward to hearing back from you and will get pics up ASAP

Well, at this moment I can only speak in general terms about this....there are thousands of varieties on this, and there is hundreds of different setups on these pumps....

So this hose might hook up on a different place on the pump....there is also another smaller hose connected to the pump casing, and its other end should be connected direct to tank (not through filter). It called case drain, and CAN NOT be restricted, kinked etc. Pressure in the case drain is a NO NO, just a little pressure will blow the shaft seal on the pump...

 

[futuresweets10]

Well, at this moment I can only speak in general terms about this....there are thousands of varieties on this, and there is hundreds of different setups on these pumps....

So this hose might hook up on a different place on the pump....there is also another smaller hose connected to the pump casing, and its other end should be connected direct to tank (not through filter). It called case drain, and CAN NOT be restricted, kinked etc. Pressure in the case drain is a NO NO, just a little pressure will blow the shaft seal on the pump...

Case drain is a 1/2in hose that runs directly from the bottom of the tank directly to the port on the pump. I will take pics later....

 

[futuresweets10]

Ok, ive got some pictures now.....

In the first pic you can see the small hydraulic line, this line runs from where you see it to the valve assembly for the front end loader, under the machine. The line on the right is the line that runs straight to the bottom of the tank.

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This next picture is a view of the front of the pump (should be pretty self explanatory) The top line is the pressure line out and the bottom line is the main line in from the tank. The valve assembly with the hard line comming out is what I assume to be my pressure and flow adjustments. This hard line runs to the back of the valve assembly thats on top of the pump (the one that is seen in the first pic)

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In this pic you can see the valve assembly on top of the pump from the back side, you can see where the other end of the hard line goes in this pic.

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And one last pic.... This shows the slight damage to the fitting on the hard line where the hard line connects to the front of the pump. This damage happened in shipping and it does not leak. From what it looks like I feel it is safe to assume the line is not restricted due to the fitting being bent, but I cant be sure.

 

[wdchyd]

You have some good advice here, Akkamaan mentions Load Sensing/variable pressure compensated pump which is spot on....JJ mentions guages....

All this means is you're gonna need technical manuals and/or a trained eye/wrench turner that knows this setup....

This pump is not like tractor gear pumps (dumb pumps)....they just move oil fixed displacement according to rpms and HP.....Pretty straightforward....

Your piston pump is what I call a smart pump.....does a lot more internally than just moving oil....It varies pressure and flow automatically....thus "Smart Pump"

Did you say this a new pump?....Why the rust on the mounting pilot and drive spline....Could it be the pump is not as new as they said when you bought it.....You may have to pull it and have CAT or Hydr Shop check out internals and have pressure tested on test stand to at least rule out pump efficiency

I think at this point if you brought this to my shop I'd pull it, open it up and at least make sure it was not trashed/worn......some people can say they rebuilt these but they only change seals....a trained eye might spot trouble inside...

Why would someone sell this pump cheaper than the 2000. Cat Pump??

I suppose if it was new from Cat the adjustments would be tweeked on their test stand before shipment....being a aftermarket unit it just might need proper adjustments....No??

 

[futuresweets10]

You have some good advice here, Akkamaan mentions Load Sensing/variable pressure compensated pump which is spot on....JJ mentions guages....

All this means is you're gonna need technical manuals and/or a trained eye/wrench turner that knows this setup....

This pump is not like tractor gear pumps (dumb pumps)....they just move oil fixed displacement according to rpms and HP.....Pretty straightforward....

Your piston pump is what I call a smart pump.....does a lot more internally than just moving oil....It varies pressure and flow automatically....thus "Smart Pump"

Did you say this a new pump?....Why the rust on the mounting pilot and drive spline....Could it be the pump is not as new as they said when you bought it.....You may have to pull it and have CAT or Hydr Shop check out internals and have pressure tested on test stand to at least rule out pump efficiency

I think at this point if you brought this to my shop I'd pull it, open it up and at least make sure it was not trashed/worn......some people can say they rebuilt these but they only change seals....a trained eye might spot trouble inside...

Why would someone sell this pump cheaper than the 2000. Cat Pump??

I suppose if it was new from Cat the adjustments would be tweeked on their test stand before shipment....being a aftermarket unit it just might need proper adjustments....No??

The people I bought the pump from could not tell me weather it was new or used. When i finally received it (fedex lost it for two weeks) it still had the factory caps over both of the ports on the back. Every indication and everthing I could find pointed to a brand new pump that had never been mounted. The paint was flawless and I could tell it hadnt been re-painted. The reason it was so cheap was because the seller was an e-bay seller who sells medical equipment and supplies that they purchase from shipping companies after its lost or not claimed. They really didnt know how they acquired the pump or really what it was. When I bought it on e-bay it had been on there several months and didnt have any application information, just a part number.

Believe it or not, the rust you see was not there when I received the pump from fed-ex, that is all 100% surface rust that occurred once the pump was installed.



Here is a pic of the pump how i got it....

 

[mmurphy]

Since you are a auto tech I would think these guys can help you out.
The best advice I can give to you is get the service manual for this machine. I would imagine the manual will run 150 bucks or more, but you will need it for other info. in the future. The manual will give a good description of what you have there, and maybe stuff you do not care.(probably help you fall asleep)Manual will also help in steps to take to determine from charge pump on up the hydraulic system.

 

[futuresweets10]

Since you are a auto tech I would think these guys can help you out.
The best advice I can give to you is get the service manual for this machine. I would imagine the manual will run 150 bucks or more, but you will need it for other info. in the future. The manual will give a good description of what you have there, and maybe stuff you do not care.(probably help you fall asleep)Manual will also help in steps to take to determine from charge pump on up the hydraulic system.

I don't know if I'm looking at the wrong thing or what, but I cant find the manual for under about 700 bucks.

 

[wdchyd]

I'm kinda surprised you didn't get any feedback from the Heavy Equip Forums that you previously posted on....it's more up their alley for sure....

 

[wdchyd]

I don't know if I'm looking at the wrong thing or what, but I cant find the manual for under about 700 bucks.

That's ironic cuz not long ago I was talking with a coworker and the conversation came up about shop manuals.....the consensus was the older the machine/the shop manual becomes more valuable than the machine itself:confused2:

 

[futuresweets10]

Well, a guy (worked for cat for years) came by the shop this morning and looked at how it was acting. He said it looks like the unloader valve (think thats what he called it) system had trash in it and it was keeping the pump from knowing it needed more pressure.

Long story short I just spent the past 5 hrs pulling one of the two valve assemblies out from under the machine and Im ready to give up. Figured it would be easy to figure out once I got it out, but I guess I was wrong. I am about ready to scrap this thing.... the pins that hold the levers to the top of the valves DO NOT COME OUT!!! If I try beating them out I am likely to bend the valve..... I FUC*ING hate cat at this point....

I obviously have bad O-rings in the bucket valve, but there is no way to replace them if I cant get the linkage off of the valve.

 

[mmurphy]

My apologies. That is absolutely rediculous. I looked on line also.

 

[futuresweets10]

I am completely lost when it comes to these valves. The valves do not appear to be able to come out of the valve body (or block) from either end. Both ends have parts attached that do not come off and look like it should pull out from the other end. There are springs, O-rings, and a TON of ball bearings that fall out with every piece you remove and no way to hold the parts back in to re-assemble. I am beginning to think that cat made the entire valve assembly to be non serviceable (even O-rings). I know a new valve assembly from cat would be a few thousand and I dont have that nor do I want to sink a few thousand into one valve assembly not knowing if the other one is bad or has problems too. It looks like cat made this machine so that if any part (pump, cylinder, valves, etc.) ever had a catastrophic failure it would cost ALOT more to fix than the machine is ever worth. The local cat shop wants about 100 an hour to look at it and they cant say what is repairable (ie, cant say if they are capable of rebuilding valves or not). This leads me to belive if I took it to them they would put brand new valves on and charge me for the labor to change them (I can change valves myself!!!!). Im at a point where I am ready to take a torch to it and scrap it...... The sad part is that they guy who came by earlier (who worked for cat) said he had never seen a machine in such great shape for its age.