I'm the guy that has posted several times lately. The boom hydraulics were working fine when i bought the machine. The drive was not good. Really jerky, lack of power (especially with turning), hydro light would flicker on and then stay on. I was told that the pumps and motors were worn out. So I had both drive pumps and both drive motors rebuilt. Got everything back together then the charge pressure light didn't work. It was just a loose connection. Fixed that and then I followed the service manual for initial start up after hydrostat overhaul. Drained lines, cooler, cylinders. Cleaned chain cases. I cranked the engine without fuel a few times till the charge light went out (It turned off really quickly). then I ran the engine at half throttle for 25 minutes on jack stands, then stoked the levers for 30 seconds to bleed the air from the motors. All seemed fine. Charge light stayed off the whole time. It was late so I left it on the jack stands until this morning. This morning I brought it down to the floor. Fired it up (charge light went out after just a second or two). Pulled it out of the garage and it was kinda jerky. Seemed to get a little better as I drove it around for a couple minutes. Then it got much worse. Basically the same as it was before the rebuild. Boom/bucket works fine. Drive is jumpy, not smooth and turning is not good at all. Then while turning around the charge light started flickering then came on. I shut it down right there in the middle of the driveway (I still need to move it but though I would ask for any help first). Where should I even start? Seriously my wife is going to kill me. I can't keep spending money like this. I already spent $3000 on the hydrostat rebuild. What else is there? Thanks for any help.
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antfarmer2
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Did you just drain the lines or did you flush them
antfarmer2
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- Oct 28, 2013
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It can take a while to get the air out make sure you keep it filled up while getting the air out or your just putting it back inDid you just drain the lines or did you flush them
antfarmer2
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Did you fill your hydro filter?It can take a while to get the air out make sure you keep it filled up while getting the air out or your just putting it back in
Thanks for helping me. I don't understand how to prefill the filters. They mount horizontally. I have topped off the fluid a few times. I only drained the lines. Don't know how to flush them but they seemed to have drained pretty well. What is driving me crazy is that it is acting exactly like it did before the hydrostatic rebuild. Do you think it could be the charge check valve?Did you fill your hydro filter?
Is the screen under the seat clean?Thanks for helping me. I don't understand how to prefill the filters. They mount horizontally. I have topped off the fluid a few times. I only drained the lines. Don't know how to flush them but they seemed to have drained pretty well. What is driving me crazy is that it is acting exactly like it did before the hydrostatic rebuild. Do you think it could be the charge check valve?
Yep. I've cleaned it several times even though it hasn't been very dirty. Just had some silicone from sealing everything up.Is the screen under the seat clean?
It's like there is enough flow to operate the boom normally and move the machine slowly and straight ahead or straight back. But as soon as I try to turn or do anythig that requires some real power it fails, moves really jerky and the hyd. charge light comes on.Yep. I've cleaned it several times even though it hasn't been very dirty. Just had some silicone from sealing everything up.
The service manual says that it is important that the charge pressure be between 150 and 190 psi. The operator's manual says that the charge light will come on if the pressure drops below 50 psi. What's up with the discrepancy? My gauge is 1/4" and the port on the pressure switch is 1/8". I'm trying to find an adapter but it's ending up hard to find. Do you think I'm barking up the wrong tree with the charge check valve?It's like there is enough flow to operate the boom normally and move the machine slowly and straight ahead or straight back. But as soon as I try to turn or do anythig that requires some real power it fails, moves really jerky and the hyd. charge light comes on.
Maybe your sending unit is bad causing the light to come on. But that should not have anything to do with it being jerkyThe service manual says that it is important that the charge pressure be between 150 and 190 psi. The operator's manual says that the charge light will come on if the pressure drops below 50 psi. What's up with the discrepancy? My gauge is 1/4" and the port on the pressure switch is 1/8". I'm trying to find an adapter but it's ending up hard to find. Do you think I'm barking up the wrong tree with the charge check valve?
You either have a bad charge check valve or you have serious internal leakage in the hydro pumps. Did you use a reputable firm to rebuild your hydro? To check if you have excessive internal leakage you will need to block the loader up again and remove the hose from the connecting line between the front and rear hydro pumps that goes to the chaincase. If I remember right it will be the small line on the left side, left side determined by standing behind the loader and facing forward, of the pumps. The line connects the two pumps to the chain case Once the hose is removed you will need to get a hose that will connect to the line between the two pumps. It will need to be long enough to reach a bucket. Start the engine and see how much oil is coming out by watching the time it takes to pump out a couple of gallons. If you have a heavy stream right away you have a bad internal leak. Stroking the hydro levers will cause a slight increase of leakage, you just need to determine how many GPM is being leaked. Take this information to the people who rebuilt the pumps. You also want a gauge attached so you can see how much the charge pressure drops when stroking the hydro levers.
Thanks again Mike. Is there typically a drop in charge pressure as the hydro levers are stroked? If so how much?You either have a bad charge check valve or you have serious internal leakage in the hydro pumps. Did you use a reputable firm to rebuild your hydro? To check if you have excessive internal leakage you will need to block the loader up again and remove the hose from the connecting line between the front and rear hydro pumps that goes to the chaincase. If I remember right it will be the small line on the left side, left side determined by standing behind the loader and facing forward, of the pumps. The line connects the two pumps to the chain case Once the hose is removed you will need to get a hose that will connect to the line between the two pumps. It will need to be long enough to reach a bucket. Start the engine and see how much oil is coming out by watching the time it takes to pump out a couple of gallons. If you have a heavy stream right away you have a bad internal leak. Stroking the hydro levers will cause a slight increase of leakage, you just need to determine how many GPM is being leaked. Take this information to the people who rebuilt the pumps. You also want a gauge attached so you can see how much the charge pressure drops when stroking the hydro levers.
The charge pressure should only drop a few psl. If it drops more than 10 psi I would think you have a leak in the pumps.Thanks again Mike. Is there typically a drop in charge pressure as the hydro levers are stroked? If so how much?
If a drop in the charge pressure indicates a leak in the pumps -- how would I tell if the charge check valve is bad? thanksThe charge pressure should only drop a few psl. If it drops more than 10 psi I would think you have a leak in the pumps.
Even if the pressure from the valve is low because of the valve it still should not drop when the hydro lever is stroked. That is why you need to see how much case drain you have from the pumps.If a drop in the charge pressure indicates a leak in the pumps -- how would I tell if the charge check valve is bad? thanks
Thanks Mike. I'm off work again on Wednesday so I'll get back to working on the L555 then. Maybe some today if I can get away early. Question. If I run a hose from the pumps to a bucket instead of the chain case, won't I run the machine low on oil pretty quickly? Is it OK to run the machine 3-4 gallons low? Also, when I check the charge check valve do I read the pressure at idle or full throttle or somewhere in between?Even if the pressure from the valve is low because of the valve it still should not drop when the hydro lever is stroked. That is why you need to see how much case drain you have from the pumps.
What would be considered "normal flow" (in GPM) from the pumps to the chain case in neutral and during hydro lever stroking? ThanksEven if the pressure from the valve is low because of the valve it still should not drop when the hydro lever is stroked. That is why you need to see how much case drain you have from the pumps.
NH does not list what the normal flow is through the case drain. If I remember right anything over 2 gpm is excessive, but I could be wrong. Unless you connect a hose to each pump the total you get by attaching a hose to the cross over pipe will be double since two pumps are sending the oil back through the line. You have close to 20 gal of oil in the system so a 5 gal loss will not cause any issue when testing. You can also just run the unit for 30 sec and double that amount for a gpm reading. If it is as I suspect you probably will not even run it that long before the bucket fills. Whatever you come up with you should be able to go to the people who rebuilt the pumps and they should be able to tell you what the normal leak rate is in the pumps. You should run the engine at high rpm when checking the charge pressure. I did find in one service manual that a 20psi drop when stroking the levers is all it should drop. Have the parking brake engaged and only stroke the lever enough to start pulling the engine down. If you pull the engine down too much it will naturally drop the charge pressure. I did find in one service manual that a 20psi drop when stroking the levers is all it should drop. This is a different system so that may not be accurate.What would be considered "normal flow" (in GPM) from the pumps to the chain case in neutral and during hydro lever stroking? Thanks
OK. Found a 1/4" to 1/8 adapter today. Plumbed in the gauge and fired it up. Gauge read 140 psi at full throttle. It dropped down to about 130 psi when I stroked the levers a little. That isn't quite the 150 - 190 psi that the service manual calls for but it doesn't seem low enough to cause the problems that I'm having. Unless someone tells me different I will move on to the pump case draining measurement on Wednesday. I just can't imagine what the hydro shop could has done to these pumps. It is not one bit better than it was before the rebuild. I know it's gonna be a fight. No one ever wants to admit when they've screwed up. These guys seemed very confident and they've been in business for a long time. Mostly do combine hydrostats and other AG equipment but they also do construction hydrostats and seem to know what they're doing -- been in business since 1986. Any other tips? I'm not looking forward to this experience.NH does not list what the normal flow is through the case drain. If I remember right anything over 2 gpm is excessive, but I could be wrong. Unless you connect a hose to each pump the total you get by attaching a hose to the cross over pipe will be double since two pumps are sending the oil back through the line. You have close to 20 gal of oil in the system so a 5 gal loss will not cause any issue when testing. You can also just run the unit for 30 sec and double that amount for a gpm reading. If it is as I suspect you probably will not even run it that long before the bucket fills. Whatever you come up with you should be able to go to the people who rebuilt the pumps and they should be able to tell you what the normal leak rate is in the pumps. You should run the engine at high rpm when checking the charge pressure. I did find in one service manual that a 20psi drop when stroking the levers is all it should drop. Have the parking brake engaged and only stroke the lever enough to start pulling the engine down. If you pull the engine down too much it will naturally drop the charge pressure. I did find in one service manual that a 20psi drop when stroking the levers is all it should drop. This is a different system so that may not be accurate.
