I've had a problem with my boom/tilt hydraulics that has slowly been getting worse. The lift and tilt speeds have gradually gotten much slower, and if i try to lift the boom and tilt the bucket at the same time, it gets really slow. The wheel drive circuit works fine, and I've got plenty of fluid. Pump problem? Relief valve? Any ideas what I should start with to troubleshoot?
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The best way is to use a flow meter to check the hyd system, but since you probably do not have one I would install a hyd pressure gauge into the aux hyd couplers on the boom. I see you have an L instead of an LX so you probably do not have them either. You will need to install a gauge into one of the cylinder lines and cap off the other cylinder line so the circuit is isolated.
Actually, I do have aux hydraulics. What pressure reading should I be expecting, and which quick-connect (male or female) should I be checking?The best way is to use a flow meter to check the hyd system, but since you probably do not have one I would install a hyd pressure gauge into the aux hyd couplers on the boom. I see you have an L instead of an LX so you probably do not have them either. You will need to install a gauge into one of the cylinder lines and cap off the other cylinder line so the circuit is isolated.
Either coupler will work you just need to move the handle in the right direction for the coupler you choose. 2750 PSI is the relief valve setting.Actually, I do have aux hydraulics. What pressure reading should I be expecting, and which quick-connect (male or female) should I be checking?
OK, I finally had some time to try this out. I put a gage on the female coupler of the aux hydraulics. When I engage, it takes a few seconds for the gage to show pressure, then it goes up to around 1000-1500 psi. I don't have a liquid filled gauge, so it jumps areound a lot. When I release the lever, the gage shows 1000 psi. Every time I engage, the same thing happens; a few seconds of low pressure followed by 1000-1500 psi. I know that the reservoir is completely full. Over-full in fact, since I had oil coming out the vent when I did this.Either coupler will work you just need to move the handle in the right direction for the coupler you choose. 2750 PSI is the relief valve setting.
Without a flow meter to isolate the pump from the control valve the next thing to look at is the relief valve in the control valve. Look for blown orings or metal in the valve itself. You could also remove the hydraulic pump and and disassemble it to check for wear or bad internal seals.OK, I finally had some time to try this out. I put a gage on the female coupler of the aux hydraulics. When I engage, it takes a few seconds for the gage to show pressure, then it goes up to around 1000-1500 psi. I don't have a liquid filled gauge, so it jumps areound a lot. When I release the lever, the gage shows 1000 psi. Every time I engage, the same thing happens; a few seconds of low pressure followed by 1000-1500 psi. I know that the reservoir is completely full. Over-full in fact, since I had oil coming out the vent when I did this.
I removed and disassembled the relief valve. O-rings were fine and the valve was clean as a whistle, so I bit the bullet and bought a new gear pump. I removed the old one and took it apart before installing the new one and all the internals looked fine. No substantial wear. I went ahead and installed the new pump anyway, and it made no difference at all. The boom/tilt/aux circuit is still very slow and jerkey and can't produce much force. I only see about 1000 psi when I put a gauge on the aux coupling. I'm really scratching my head now. What else could it be? Clogged suction line to the gear pump?Without a flow meter to isolate the pump from the control valve the next thing to look at is the relief valve in the control valve. Look for blown orings or metal in the valve itself. You could also remove the hydraulic pump and and disassemble it to check for wear or bad internal seals.
You did not mention that the hydraulics were jerky in your original post. There is no screen on the suction side of the pump. You have a hose from the pump to the oil reservoir. You can remove the hose and see if the inside is colasping or if the hose clamps are loose. To keep from throwing more money at the problem you really need someone with a flow meter to check the system. You can probably do some of the checks on your own but by the time you buy the fittings, gauges and shut off valve it would be less expensive to just have someone check it. Also if you do not know what you are doing when isolating the pump form the rest of the system you could blow up your new pump.I removed and disassembled the relief valve. O-rings were fine and the valve was clean as a whistle, so I bit the bullet and bought a new gear pump. I removed the old one and took it apart before installing the new one and all the internals looked fine. No substantial wear. I went ahead and installed the new pump anyway, and it made no difference at all. The boom/tilt/aux circuit is still very slow and jerkey and can't produce much force. I only see about 1000 psi when I put a gauge on the aux coupling. I'm really scratching my head now. What else could it be? Clogged suction line to the gear pump?
I'll see if I can get in to have a look at the suction hose. If I can't, or if it all looks OK, then I'm out of ideas and it'll have to to the dealer, who can do a flow test. Thanks for all the help.You did not mention that the hydraulics were jerky in your original post. There is no screen on the suction side of the pump. You have a hose from the pump to the oil reservoir. You can remove the hose and see if the inside is colasping or if the hose clamps are loose. To keep from throwing more money at the problem you really need someone with a flow meter to check the system. You can probably do some of the checks on your own but by the time you buy the fittings, gauges and shut off valve it would be less expensive to just have someone check it. Also if you do not know what you are doing when isolating the pump form the rest of the system you could blow up your new pump.
I was able to check the hoses from the reservoir to the pump suction and from the hydraulic oil filter to the reservoir. Both are clean and not collapsed. I spoke to the local NH service tech and he said that after all I've done, the problem most likely is in the control valve. I see that there's a rebuild kit available and judging from the drawings it looks like I should be able to take it apart, check for blockages, and replace the seals pretty easily, unless I'm missing something. Can the valve be removed through the access panel in front of the seat, or does the cab need to be tilted?I'll see if I can get in to have a look at the suction hose. If I can't, or if it all looks OK, then I'm out of ideas and it'll have to to the dealer, who can do a flow test. Thanks for all the help.
All the seal kit will do for you is seal for leakage to the outside. It has nothing to do with the internal workings of the valve. The valve will come out the front but you may need to remove the steering pods so you can loosen all the lines. I do not think there is much difference in the price of the seal kit and the relief valve. If I had to choose I would choose the relief valve but then it is always easier spending someone else's money. Even if you had a blockage in the valve it should still build pressure or else your relief valve would be bypassing all the time and you would certainly notice it from the engine at idle. I would still like to install a flow meter between the pump and the valve though I would agree with the person you talked with that the problem is probably in the valve. I just have an aversion to thowing parts at a problem hoping that I guessed right.I was able to check the hoses from the reservoir to the pump suction and from the hydraulic oil filter to the reservoir. Both are clean and not collapsed. I spoke to the local NH service tech and he said that after all I've done, the problem most likely is in the control valve. I see that there's a rebuild kit available and judging from the drawings it looks like I should be able to take it apart, check for blockages, and replace the seals pretty easily, unless I'm missing something. Can the valve be removed through the access panel in front of the seat, or does the cab need to be tilted?
Well, I feel pretty foolish, but I figured out the main problem. When I said early on that I had checked the relief valve, it was the boom circuit relief valve that I checked. I didn't realize that there were two relief valves until I went through the control valve drawings trying to figure out if I could tackle the rebuild. The main relief valve had a small piece of debris stuck in it. I'm now seeing about 2700 psi at the aux connectors. However, the boom is still jerky when I raise it. I greased everything up and it's still not smooth. It goes down perfectly smoothly so I'm thinking that this is a hydraulic issue and not mechanical binding. If I engage the aux hydraulics at the same time I raise the boom, the pressure drops to about 1000 psi, but it is stable. The boom does go all the way up, just not smoothly. Any ideas on this?All the seal kit will do for you is seal for leakage to the outside. It has nothing to do with the internal workings of the valve. The valve will come out the front but you may need to remove the steering pods so you can loosen all the lines. I do not think there is much difference in the price of the seal kit and the relief valve. If I had to choose I would choose the relief valve but then it is always easier spending someone else's money. Even if you had a blockage in the valve it should still build pressure or else your relief valve would be bypassing all the time and you would certainly notice it from the engine at idle. I would still like to install a flow meter between the pump and the valve though I would agree with the person you talked with that the problem is probably in the valve. I just have an aversion to thowing parts at a problem hoping that I guessed right.