L555 Please save me from divorce!

[Mike10]

The new gear pump arrived today. I promptly removed the old pump and installed the new pump. Exchange was simple and quick. Then I removed the line bypassing the control valve and reinstalled the hose from the gear pump outlet to the control valve. Started it up and the charge pressure was at 150 psi. Backed it out of the garage and drove around a little. The dang thing is operating just like before the new pump($225), which is just like before the new charge check valve($110), which is just like before the rebuilt hydrostatic pumps($1600), which is just like before the rebuilt drive motors ($1300). I'm running out of parts to replace on this thing. I'm really at my wit's end. Please help me figure this out. I'm obviously too far in ($$$$$) to give up now. Thanks again, Brett

I would still like to know what the flow is to the hydro pumps by using a flow meter. First though you might want to install another gauge in the outlet side of the oil cooler circuit to see if the two pressure readings are the same. Have you talked to the person who rebuilt your pumps to see what the normal case drain is for those pumps? Your case drain does not seem right. There should only be two conditions which would cause the charge pressure to drop, excess case drain or a restriction in the flow of oil to the pumps before the oil pressure sender. Evidently your case drain is below normal even after plugging the hoses to the motors.

 

[palmtree]

I would still like to know what the flow is to the hydro pumps by using a flow meter. First though you might want to install another gauge in the outlet side of the oil cooler circuit to see if the two pressure readings are the same. Have you talked to the person who rebuilt your pumps to see what the normal case drain is for those pumps? Your case drain does not seem right. There should only be two conditions which would cause the charge pressure to drop, excess case drain or a restriction in the flow of oil to the pumps before the oil pressure sender. Evidently your case drain is below normal even after plugging the hoses to the motors.

How about if I ran my bypass hose from the outlet of the gear pump to just before the Tee fitting before the charge check valve?

 

[palmtree]

How about if I ran my bypass hose from the outlet of the gear pump to just before the Tee fitting before the charge check valve?

That would bypass the control valve and the oil cooler. I can't really get any closer to the hydro pumps without bypassing the charge check valve, and I'm thinking I shouldn't send full gear pump pressure to the hydros.

 

[Mike10]

That would bypass the control valve and the oil cooler. I can't really get any closer to the hydro pumps without bypassing the charge check valve, and I'm thinking I shouldn't send full gear pump pressure to the hydros.

I still think if there was a restriction after the oil cooler but before the check valve, you would blow the oil cooler apart. You already know there is not a restriction between the hyd pump and the outlet of the cooler since you already bypassed the control valve and the cooler. Now if you install an addional gauge at the outlet of the cooler and you find you have high pressure then you can assume there is a restriction after the cooler. If you find the charge pressure remains constant at the cooler while the gauge at the sender port drops then you know there is a problem from the check valve to the outlet of the filter or you have a leakage problem in the hydro. A leakage problem at the hydro should be evident from a high volume of case drain, which you do not have.

 

[jerry]

I still think if there was a restriction after the oil cooler but before the check valve, you would blow the oil cooler apart. You already know there is not a restriction between the hyd pump and the outlet of the cooler since you already bypassed the control valve and the cooler. Now if you install an addional gauge at the outlet of the cooler and you find you have high pressure then you can assume there is a restriction after the cooler. If you find the charge pressure remains constant at the cooler while the gauge at the sender port drops then you know there is a problem from the check valve to the outlet of the filter or you have a leakage problem in the hydro. A leakage problem at the hydro should be evident from a high volume of case drain, which you do not have.

Do as Mike says and follow the flow from item to item before replacing anything. Could be a piece of rag or some other obstruction in a hose or port along the path. It has happened before.

 

[antfarmer2]

Do as Mike says and follow the flow from item to item before replacing anything. Could be a piece of rag or some other obstruction in a hose or port along the path. It has happened before.

Is your oil still foamy?.......is your oil filter right and on proper

 

[palmtree]

Is your oil still foamy?.......is your oil filter right and on proper

The oil really doesn't seem to be very foamy anymore. It hasn't been foamy for quite a while now. I think that was just from initial start up after draining everything down while the hydros were out. I'm not sure how to go about checking the pressure at different spots. The only port I can find is where the pressure switch is installed just downstream of the filter. Do I need to get a fitting that has a gauge port and tie it in at different places?

 

[palmtree]

The oil really doesn't seem to be very foamy anymore. It hasn't been foamy for quite a while now. I think that was just from initial start up after draining everything down while the hydros were out. I'm not sure how to go about checking the pressure at different spots. The only port I can find is where the pressure switch is installed just downstream of the filter. Do I need to get a fitting that has a gauge port and tie it in at different places?

I've been thinking. It seems like I should focus my search down to the lines between the TEE where one side goes to the charge check valve and the other goes to the filter prior to the hydrostats. Maybe there is some sort of restriction between that TEE and the filter? It's about the only place left to look. I already ran a hose from the output of the gear pump straight to the input of the oil cooler (ran a little better but still not right at all). I've also already bypassed the oil cooler with a hose (ran the same as before). Makes sense that the restriction may be after the TEE to the check valve doesn't it?

 

[palmtree]

I've been thinking. It seems like I should focus my search down to the lines between the TEE where one side goes to the charge check valve and the other goes to the filter prior to the hydrostats. Maybe there is some sort of restriction between that TEE and the filter? It's about the only place left to look. I already ran a hose from the output of the gear pump straight to the input of the oil cooler (ran a little better but still not right at all). I've also already bypassed the oil cooler with a hose (ran the same as before). Makes sense that the restriction may be after the TEE to the check valve doesn't it?

what pressure range should the gauge be? I know it should only be charge pressure - but I guess that it could be much higher pressure if I tap in upstream of a significant restriction.

 

[Mike10]

what pressure range should the gauge be? I know it should only be charge pressure - but I guess that it could be much higher pressure if I tap in upstream of a significant restriction.

I would think a 300 lb pressure gauge will work. I was mistaken about you bypassing the cooler, but I still think the problem is down stream from there. The least expensive place to install a pressure gauge is at the tee the cooler out line attaches to at the oil filters and check valve. Remove the tee, drill a hole in the flat center section of the tee and tap threads for the pressure gauge. Afterwards you can put a pipe plug in the hole. I would disconnect this cooler line from the cooler an blow air through it to make sure it is open while the top end is disconnected from the tee.

 

[palmtree]

I would think a 300 lb pressure gauge will work. I was mistaken about you bypassing the cooler, but I still think the problem is down stream from there. The least expensive place to install a pressure gauge is at the tee the cooler out line attaches to at the oil filters and check valve. Remove the tee, drill a hole in the flat center section of the tee and tap threads for the pressure gauge. Afterwards you can put a pipe plug in the hole. I would disconnect this cooler line from the cooler an blow air through it to make sure it is open while the top end is disconnected from the tee.

Update. I don't have any new tools yet so here's what I did today. I removed the hard line between the charge check valve TEE and the filter just before the hydrostatic pumps. All is clear including the TEE. Then I removed the hard line between the other side (upstream side) of the TEE and the outlet of the oil cooler. That one was all clear too. I was able to easily blow through it with my mouth and even able to easily blow a steel ball that was large enough that it would go through a 90 degree turn without blowing. But when I blew with my mouth it shot out the other side easily. So I didn't learn anything new today. I did however manage to win an ebay auction for a Hedland flow meter http://www.grainger.com/product/HEDLAND-Flowmeter-4NMW7. It's used and I snagged it for only $27 so I hope it works. Supposedly it works fine. That won't be here until the end of the week. So where should I mount that meter when it arrives? I would think just before the hydro pumps. Any tips to using one of them?

 

[palmtree]

Update. I don't have any new tools yet so here's what I did today. I removed the hard line between the charge check valve TEE and the filter just before the hydrostatic pumps. All is clear including the TEE. Then I removed the hard line between the other side (upstream side) of the TEE and the outlet of the oil cooler. That one was all clear too. I was able to easily blow through it with my mouth and even able to easily blow a steel ball that was large enough that it would go through a 90 degree turn without blowing. But when I blew with my mouth it shot out the other side easily. So I didn't learn anything new today. I did however manage to win an ebay auction for a Hedland flow meter http://www.grainger.com/product/HEDLAND-Flowmeter-4NMW7. It's used and I snagged it for only $27 so I hope it works. Supposedly it works fine. That won't be here until the end of the week. So where should I mount that meter when it arrives? I would think just before the hydro pumps. Any tips to using one of them?

I still haven't received the flow meter. I've been thinking though. My gut says that I'm gonna have low flow everywhere I check the system. I'm starting to think that there may be something blocking the oil pickup at the stand pipe. I've removed and cleaned the suction filter many times but I've never checked to be sure the pipe is clear where it originates from the cross tube under the floor. Any tricks to check this without draining the oil again. I don't want to drain the oil before I am able to run some tests with the flow meter. Thanks again, Brett

 

[palmtree]

I still haven't received the flow meter. I've been thinking though. My gut says that I'm gonna have low flow everywhere I check the system. I'm starting to think that there may be something blocking the oil pickup at the stand pipe. I've removed and cleaned the suction filter many times but I've never checked to be sure the pipe is clear where it originates from the cross tube under the floor. Any tricks to check this without draining the oil again. I don't want to drain the oil before I am able to run some tests with the flow meter. Thanks again, Brett

I received the flow meter the other day. It looks good but it is pretty big. It's not gonna be easy squeezing that thing in anywhere. I'm gonna need to get some hoses made up and also need some 90 degree fittings. It came with JIC 8 male fittings on each end. I have some JIC 12 male fittings that I could put on it but I can't get the them off for the life of me. I quit trying because I'm going to need some 90 degree fittings anyway. Hopefully I can get all that together this weekend. I'm planning on mounting the flow meter just after the gear pump initially. Then mounting it just before the hydrostatic pumps for comparison. Does that sound reasonable? Thanks again. Brett

 

[Mike10]

I received the flow meter the other day. It looks good but it is pretty big. It's not gonna be easy squeezing that thing in anywhere. I'm gonna need to get some hoses made up and also need some 90 degree fittings. It came with JIC 8 male fittings on each end. I have some JIC 12 male fittings that I could put on it but I can't get the them off for the life of me. I quit trying because I'm going to need some 90 degree fittings anyway. Hopefully I can get all that together this weekend. I'm planning on mounting the flow meter just after the gear pump initially. Then mounting it just before the hydrostatic pumps for comparison. Does that sound reasonable? Thanks again. Brett

That should work. The only concern I have is the flow meter has a min of 3GPM, may not go low enough to show you any flow at the pumps. Have the loader blocked up and stroke the levers when checking at the pumps.

 

[palmtree]

That should work. The only concern I have is the flow meter has a min of 3GPM, may not go low enough to show you any flow at the pumps. Have the loader blocked up and stroke the levers when checking at the pumps.

Will do. Hopefully I can get to it on Wednesday. Thanks

 

[palmtree]

Will do. Hopefully I can get to it on Wednesday. Thanks

Update. Flow meter inline just after the gear pump shows 15 GPM. Then I installed the flow meter just before the hydrostatic pumps and put the machine up on jack stands. The meter read just over 3 GPM (15 liters per minute) at full throttle with the levers wide upen and the wheels spinning full speed. What does this mean. It sounds low to me but I'm not sure. I have checked everywhere I can think of for a restriction or blockage. Any ideas. Thanks again. Brett

 

[Mike10]

Update. Flow meter inline just after the gear pump shows 15 GPM. Then I installed the flow meter just before the hydrostatic pumps and put the machine up on jack stands. The meter read just over 3 GPM (15 liters per minute) at full throttle with the levers wide upen and the wheels spinning full speed. What does this mean. It sounds low to me but I'm not sure. I have checked everywhere I can think of for a restriction or blockage. Any ideas. Thanks again. Brett

The only oil that will go to the hydrostats is to replace oil that has leaked back through the case drains. The system is basically a closed loop system with the oil added from the hydraulic pump only to the degree oil leaks past the pistions. 3GPM would appear to be close to normal with both sides running at the same time............Did you also have your pressure gauge installed to check charge pressure?......... If the flow held steady at 3gpm the charge pressure should also have held steady. Did you run it long enough to heat up the oil? Dead heading the control valve is a good way to get the oil to operating temperature.... One other thing you might check is to ever so slightly move one of the levers so the motor just barely turns. See if there is a slow down and speed up of the motor. It barely needs to be moving and you must hold the lever steady....I once had one that did what you mention on only one side but not as bad as yours and only in reverse. When I check loaders I barely stroke the levers, one at a time, forward and backward to see if there is that slow down and speed up of the motor. It took a new motor to correct the problem. The original motor internal parts looked like new and I resealed and shimmed the motor to specs and it still did the slow down and speed up... I hope that is not your problem, but the charge pressure thing is what seems strange. I think you need to see what will actually flow through the hose to the hydro pumps. To do this you will need to disconnect the hose from the pumps and run it to a bucket. Start the engine and only run long enough to see if the flow increases substantially. I would think you should see close to what the hydraulic pump flow is. Remember the pumps are turning without any new oil so be quick to avoid any damage. Run long enough to get a reading then shut down.... Sorry for the rambling, just thinking out loud.

 

[palmtree]

The only oil that will go to the hydrostats is to replace oil that has leaked back through the case drains. The system is basically a closed loop system with the oil added from the hydraulic pump only to the degree oil leaks past the pistions. 3GPM would appear to be close to normal with both sides running at the same time............Did you also have your pressure gauge installed to check charge pressure?......... If the flow held steady at 3gpm the charge pressure should also have held steady. Did you run it long enough to heat up the oil? Dead heading the control valve is a good way to get the oil to operating temperature.... One other thing you might check is to ever so slightly move one of the levers so the motor just barely turns. See if there is a slow down and speed up of the motor. It barely needs to be moving and you must hold the lever steady....I once had one that did what you mention on only one side but not as bad as yours and only in reverse. When I check loaders I barely stroke the levers, one at a time, forward and backward to see if there is that slow down and speed up of the motor. It took a new motor to correct the problem. The original motor internal parts looked like new and I resealed and shimmed the motor to specs and it still did the slow down and speed up... I hope that is not your problem, but the charge pressure thing is what seems strange. I think you need to see what will actually flow through the hose to the hydro pumps. To do this you will need to disconnect the hose from the pumps and run it to a bucket. Start the engine and only run long enough to see if the flow increases substantially. I would think you should see close to what the hydraulic pump flow is. Remember the pumps are turning without any new oil so be quick to avoid any damage. Run long enough to get a reading then shut down.... Sorry for the rambling, just thinking out loud.

Thanks Mike. When I had the flow meter on the gear pump I was able to drive it around and get it warm. After a few minutes the charge pressure was down to about 120 psi or so and would drop when turning. The flow meter was steady at 15 GPM. About the motors. You want me to stroke the levers slowly and see if the motors also move slowly or whether they are jumpy? Should this be done on jack stands or while driving on the ground? Shop said the motors have all new rotating assemblies.

 

[palmtree]

Thanks Mike. When I had the flow meter on the gear pump I was able to drive it around and get it warm. After a few minutes the charge pressure was down to about 120 psi or so and would drop when turning. The flow meter was steady at 15 GPM. About the motors. You want me to stroke the levers slowly and see if the motors also move slowly or whether they are jumpy? Should this be done on jack stands or while driving on the ground? Shop said the motors have all new rotating assemblies.

I should have a couple hours tomorrow morning to work on the skid steer. It's still up on jack stands and the flow meter is still in place just before the hydro pumps. I was thinking that maybe before I remove the flow meter from that location I should test it again but this time stroking the levers with the parking brake on. That should put a load on the motors and pumps. If either of those are failing under load (as in when I'm turning) then shouldn't I see an increase in flow to hydro pumps? I'll also try that test you mentioned by slowly and slightly stroking one lever at a time to look for spontaneous slow down and speed up of the motors. Should I leave the flow meter attached when I check the flow to the pumps without supplying the pumps and discharging in a bucket or just run a hose to the bucket? I agree that the charge pressure is the mystery. Why would it creep down? After it's warmed up it will hover around 120 psi and dip quickly when under load. If the gear pump is continually pumping 15 gpm and the hydro pumps are only getting 3 gpm then how can the pressure dip below that of the charge pressure check valve (160 psi)? All that oil must be going somewhere and it should not be going through the charge check valve at 120 psi. I'll keep an eye on that tomorrow when I run these tests. By the way -- I've never seen the charge pressure over 150 psi, never 160 psi as I think it should be with a brand new charge check valve. Any other ideas or tips would be greatly appreciated.

 

[Mike10]

I should have a couple hours tomorrow morning to work on the skid steer. It's still up on jack stands and the flow meter is still in place just before the hydro pumps. I was thinking that maybe before I remove the flow meter from that location I should test it again but this time stroking the levers with the parking brake on. That should put a load on the motors and pumps. If either of those are failing under load (as in when I'm turning) then shouldn't I see an increase in flow to hydro pumps? I'll also try that test you mentioned by slowly and slightly stroking one lever at a time to look for spontaneous slow down and speed up of the motors. Should I leave the flow meter attached when I check the flow to the pumps without supplying the pumps and discharging in a bucket or just run a hose to the bucket? I agree that the charge pressure is the mystery. Why would it creep down? After it's warmed up it will hover around 120 psi and dip quickly when under load. If the gear pump is continually pumping 15 gpm and the hydro pumps are only getting 3 gpm then how can the pressure dip below that of the charge pressure check valve (160 psi)? All that oil must be going somewhere and it should not be going through the charge check valve at 120 psi. I'll keep an eye on that tomorrow when I run these tests. By the way -- I've never seen the charge pressure over 150 psi, never 160 psi as I think it should be with a brand new charge check valve. Any other ideas or tips would be greatly appreciated.

Leave the flow meter in place when you remove the hose from the pumps. I want to see if we get more than 3 gpm then. Your charge pressure will be low because of the increase flow though the hose. Don't run any longer than necessary when you do this test. I have also thought about capping the hose to the pumps to see if the charge pressure would increase. If it does not, then the check valve or your gauge is at fault....When you get it back on the ground then try easing the levers forward to see if the motors speed up and slow down. The one I had I installed a flow meter to the motors with a gauge and you could watch the gauge pressure increase and decrease as the motor rotated. I had it up on stands when I did that. If you try an install a gauge in the high pressure circuit to the motors use a 6000 lb gauge or be sure you do not dead head the hydro pumps beyond what your gauge will take. I myself prefer a lower pressure gauge because it is easier to see the fluctuations.