mark100pe
New Member
ASV PT100 Lift Arm problems
Serial Number PTD03785 Approx. 1,700 hours on machine.
I’ve been working on the above machine for days and can’t figure out what is going on. Here is a long explanation of what is occurring. I wanted to provide as many details as possible. I’d really appreciate anyone’s help with this problem. There are no ASV dealers close to me and I’ve always been able to fix these machines myself. This is the second one I’ve owned. However, I’m at a loss for what to do next…
The lift arms started behaving strangely a couple months ago for no apparent reason. It started off with the arms only traveling in one position regardless of which way you operated the joy stick. As I recall, they arms would only go up whether the joy stick was pushed forward or pulled back. Took the machine into my shop, hooked up a pressure gauge on the “test port C” to test the Lift Arm Pressure. (per Page 14-4 of Service Manual). The arms then started working properly, even though I had done nothing to the machine!
I went ahead and tested the fully up and fully down lift arm pressures at Port C. When the arms were in the highest position and reached the stop, the pressure was only 2,400 psi. When arms were down in the lowest position, the pressure was 3,400 psi. The manual says the pressure should be 3300 +/- 100 psi in both positions, so I assumed the pressure relief valve was bad and ordered a new one. While waiting for the part to arrive, I continued to look over the machine and test the arm pressure. When I checked the pressure again, both the up and down pressures were now reaching 3,400 psi, even though I hadn’t made any changes or fixed anything! Therefore, I kept the pressure relief valve, but didn’t install it.
I noticed that the engine seems to be laboring a little when I bring the lift arms down. I noticed that the temperature of the right hand cylinder felt hot to the touch, hotter than the other cylinder. I checked the temps with a laser thermometer and the one cylinder and hoses were a good 20 degrees hotter than the cylinder and hoses on the other side. I decided to disconnect the right side cylinder from the arm mounts, but leave the hoses connected to the cylinder. Therefore, the left arm cylinder was hooked up as normal, but the right arm cylinder could expand and contract without moving the machine arms. When I tested the machine like that, the right cylinder would not move at all! It would neither expand nor retract, even though it had no load from the arms of the machine on it. The other cylinder (left arm) raised the arms of the machine up and down. I decided the right cylinder must be partially bound up somehow. There was no oil leaking from the seals that I could see and I don’t think it was leaking past the piston, since there was no load on the cylinder. It should have easily retracted and expanded. Since I was anxious to get the machine back in service, I decided to just buy a new cylinder, as opposed to taking the other apart. I figured when my work load lightened, I’d take it apart and figure out what happened, but for now I just needed to get the machine back in service. I put the new cylinder on and put it all back together, but the lift arms still were not working right.
I decided to put in-line pressure gauges on the lines connected to the lift arm cylinders. I installed four tees and four 3,000 psi gauges on the two cylinders. One at each extend and retract port. I then tested the lift arms and got the following results. When I raised the arms (extend cylinder), I got 300 psi on the extension side of both cylinders and 0 psi on the retraction side. This is what I would have expected. There was no load on the arms, so it took a minimal amount of pressure (300 psi) to lift the arms. However, when I lowered the arms (retracted cylinder) I got strange results. While lowering, the right cylinder (new cylinder) had 1,300 psi on the extension side and 2,000 psi on the retraction side. I would have expected to have no pressure on the extension side and minimal on the retraction side. The left cylinder behaved similarly but with higher pressures. The extension side of the left cylinder was at 1,700 psi and the retraction side was at 2,200 psi. In addition, the machine sounded like it was laboring a little. When I let go of the joy stick, the pressures remained high on the gauges and then slowly dropped (around 50 psi per second or even slower). When I raised the arms and let go of the joy stick, the pressures immediately dropped to zero on all the gauges. The residual pressures only remained when I lowered the arms (cylinders retracting).
From this, I concluded that it appears to act as if I’m somehow getting “back pressure” on the extend ports of the cylinders when I shouldn’t have any. To overcome this back pressure, the retract pressure has to be much higher than normal. When I let go of the joystick, the back pressure remains. It then slowly bleeds down.
It is my understanding that the hydraulic lines that feed the cylinders are connected together with Y connections; the lines connected to the cylinder extend ports are connected together and then connect to the extend port on the Loader Control Valve. Likewise, the lines connected to the cylinder retract ports are connected together and then connect to the retract port on the Loader Control Valve. Therefore, I don’t understand why the pressure would be higher on the left side than on the right side.
Being totally confused and frustrated by these results, I decided to disconnect both cylinders from the mounts, but leave the hoses connected. Therefore, both cylinders should be able to extend and retract with no load whatsoever on them. When I did this, the right cylinder extended and retracted, but the left cylinder did not move. It would neither extend nor retract. I thought, OK, maybe the left cylinder is also damaged (bent rod or something that prevents it from moving), so I disconnected the left cylinder hoses and capped both hoses. Therefore, the right cylinder was now the only cylinder connected to the system and it was still not connected to the arms, so it should be able to move freely with no restricting force on either side. However, when I test it, I end up still having a lot of back pressure on the retract side of the cylinder. When I move the joy stick to raise the arms (extend the cylinder), the system seems to work normal and as expected. The right cylinder extends fine with very minimal pressure on both ports. However, when I retract the right cylinder, I get high pressure on the retract side (3,400 psi) and 1,200 psi on the extend side.
A rep from ASV suggested switching the hoses on the joy stick controller to see if the problem then switches from the retracting side to the extending side. Switching the hoses reversed the operation of the joy stick, as you would expect. Pulling the joy stick back now retracted the cylinder (would lower the arms if cylinder was connected to arms) and pushing joy stick forward extended the cylinder (raised the arms). However, the problem with the pressures on the cylinder ports did not change. Retracting the cylinder still caused high readings on both ports. If I retract the cylinder with light pressure on the joy stick, the pressure on the extend port is 500 psi and 1,500 psi on the retract port. If I use heavy pressure on the joy stick, the extend port pressure is 1,500 psi and the retract port pressure is 3,000 psi. If I let go of the joy stick at mid stroke while retracting, the pressure remains on both ports.
An interesting thing happens when I fully retract the cylinder until it can retract no more; the extend port pressure drops to zero and the retract port pressure jumps to 3,400 (relief pressure). This behavior is the same as occurs when extending the cylinder. The pressure is essentially zero on the extend and retract port when extending the cylinder and then when it reaches its maximum extension the extend port pressure jumps to 3,300 psi and the retract port remains at zero.
Therefore, it would appear as if whatever is causing the back pressure on the extend port when the cylinder is retracting stops doing that when the cylinder is fully retracted.
The above information seems to be pointing me towards the Loader Control Valve, but I don’t understand how this valve operates. Is it possible that when the extend function is activated (arms being raised), the retract port is open back to the tank (creating no back pressure on the retract port), but when the retract function is activated (arms being lowered), the extend port is not open back to the tank, but instead is pressurized. The retract port then has to produce more pressure to overcome the back pressure, causing the retract port at the cylinder to be 1,500 psi to 3,400 psi (depending upon the force being applied to the joy stick) and the pressure at the extend port of the cylinder to be 500 to 1,500 psi?
I would greatly appreciate any feedback you guys could provide on the following questions:
1) Can one of the two lift cylinders be removed and the hoses capped and the remaining cylinder should still work fine?
2) Are the lines to the cylinder ports connected together via a Y or Tee? If this is correct, how could I have higher pressure on one arm cylinder vs. the other, unless there is blockage in one of the lines. If one line was blocked, it should behave that way all the time, which it doesn’t.
3) When the extend port on the Lift Control Valve is activated should the retract port open to the return tank (zero pressure in line) and when the retract port on the Lift Control Valve is activated should the extend port open to the return tank (zero pressure in line).
4) If the above assumptions are correct, any idea as to why it is not working correctly and what I should look at next?
Thanks!
Serial Number PTD03785 Approx. 1,700 hours on machine.
I’ve been working on the above machine for days and can’t figure out what is going on. Here is a long explanation of what is occurring. I wanted to provide as many details as possible. I’d really appreciate anyone’s help with this problem. There are no ASV dealers close to me and I’ve always been able to fix these machines myself. This is the second one I’ve owned. However, I’m at a loss for what to do next…
The lift arms started behaving strangely a couple months ago for no apparent reason. It started off with the arms only traveling in one position regardless of which way you operated the joy stick. As I recall, they arms would only go up whether the joy stick was pushed forward or pulled back. Took the machine into my shop, hooked up a pressure gauge on the “test port C” to test the Lift Arm Pressure. (per Page 14-4 of Service Manual). The arms then started working properly, even though I had done nothing to the machine!
I went ahead and tested the fully up and fully down lift arm pressures at Port C. When the arms were in the highest position and reached the stop, the pressure was only 2,400 psi. When arms were down in the lowest position, the pressure was 3,400 psi. The manual says the pressure should be 3300 +/- 100 psi in both positions, so I assumed the pressure relief valve was bad and ordered a new one. While waiting for the part to arrive, I continued to look over the machine and test the arm pressure. When I checked the pressure again, both the up and down pressures were now reaching 3,400 psi, even though I hadn’t made any changes or fixed anything! Therefore, I kept the pressure relief valve, but didn’t install it.
I noticed that the engine seems to be laboring a little when I bring the lift arms down. I noticed that the temperature of the right hand cylinder felt hot to the touch, hotter than the other cylinder. I checked the temps with a laser thermometer and the one cylinder and hoses were a good 20 degrees hotter than the cylinder and hoses on the other side. I decided to disconnect the right side cylinder from the arm mounts, but leave the hoses connected to the cylinder. Therefore, the left arm cylinder was hooked up as normal, but the right arm cylinder could expand and contract without moving the machine arms. When I tested the machine like that, the right cylinder would not move at all! It would neither expand nor retract, even though it had no load from the arms of the machine on it. The other cylinder (left arm) raised the arms of the machine up and down. I decided the right cylinder must be partially bound up somehow. There was no oil leaking from the seals that I could see and I don’t think it was leaking past the piston, since there was no load on the cylinder. It should have easily retracted and expanded. Since I was anxious to get the machine back in service, I decided to just buy a new cylinder, as opposed to taking the other apart. I figured when my work load lightened, I’d take it apart and figure out what happened, but for now I just needed to get the machine back in service. I put the new cylinder on and put it all back together, but the lift arms still were not working right.
I decided to put in-line pressure gauges on the lines connected to the lift arm cylinders. I installed four tees and four 3,000 psi gauges on the two cylinders. One at each extend and retract port. I then tested the lift arms and got the following results. When I raised the arms (extend cylinder), I got 300 psi on the extension side of both cylinders and 0 psi on the retraction side. This is what I would have expected. There was no load on the arms, so it took a minimal amount of pressure (300 psi) to lift the arms. However, when I lowered the arms (retracted cylinder) I got strange results. While lowering, the right cylinder (new cylinder) had 1,300 psi on the extension side and 2,000 psi on the retraction side. I would have expected to have no pressure on the extension side and minimal on the retraction side. The left cylinder behaved similarly but with higher pressures. The extension side of the left cylinder was at 1,700 psi and the retraction side was at 2,200 psi. In addition, the machine sounded like it was laboring a little. When I let go of the joy stick, the pressures remained high on the gauges and then slowly dropped (around 50 psi per second or even slower). When I raised the arms and let go of the joy stick, the pressures immediately dropped to zero on all the gauges. The residual pressures only remained when I lowered the arms (cylinders retracting).
From this, I concluded that it appears to act as if I’m somehow getting “back pressure” on the extend ports of the cylinders when I shouldn’t have any. To overcome this back pressure, the retract pressure has to be much higher than normal. When I let go of the joystick, the back pressure remains. It then slowly bleeds down.
It is my understanding that the hydraulic lines that feed the cylinders are connected together with Y connections; the lines connected to the cylinder extend ports are connected together and then connect to the extend port on the Loader Control Valve. Likewise, the lines connected to the cylinder retract ports are connected together and then connect to the retract port on the Loader Control Valve. Therefore, I don’t understand why the pressure would be higher on the left side than on the right side.
Being totally confused and frustrated by these results, I decided to disconnect both cylinders from the mounts, but leave the hoses connected. Therefore, both cylinders should be able to extend and retract with no load whatsoever on them. When I did this, the right cylinder extended and retracted, but the left cylinder did not move. It would neither extend nor retract. I thought, OK, maybe the left cylinder is also damaged (bent rod or something that prevents it from moving), so I disconnected the left cylinder hoses and capped both hoses. Therefore, the right cylinder was now the only cylinder connected to the system and it was still not connected to the arms, so it should be able to move freely with no restricting force on either side. However, when I test it, I end up still having a lot of back pressure on the retract side of the cylinder. When I move the joy stick to raise the arms (extend the cylinder), the system seems to work normal and as expected. The right cylinder extends fine with very minimal pressure on both ports. However, when I retract the right cylinder, I get high pressure on the retract side (3,400 psi) and 1,200 psi on the extend side.
A rep from ASV suggested switching the hoses on the joy stick controller to see if the problem then switches from the retracting side to the extending side. Switching the hoses reversed the operation of the joy stick, as you would expect. Pulling the joy stick back now retracted the cylinder (would lower the arms if cylinder was connected to arms) and pushing joy stick forward extended the cylinder (raised the arms). However, the problem with the pressures on the cylinder ports did not change. Retracting the cylinder still caused high readings on both ports. If I retract the cylinder with light pressure on the joy stick, the pressure on the extend port is 500 psi and 1,500 psi on the retract port. If I use heavy pressure on the joy stick, the extend port pressure is 1,500 psi and the retract port pressure is 3,000 psi. If I let go of the joy stick at mid stroke while retracting, the pressure remains on both ports.
An interesting thing happens when I fully retract the cylinder until it can retract no more; the extend port pressure drops to zero and the retract port pressure jumps to 3,400 (relief pressure). This behavior is the same as occurs when extending the cylinder. The pressure is essentially zero on the extend and retract port when extending the cylinder and then when it reaches its maximum extension the extend port pressure jumps to 3,300 psi and the retract port remains at zero.
Therefore, it would appear as if whatever is causing the back pressure on the extend port when the cylinder is retracting stops doing that when the cylinder is fully retracted.
The above information seems to be pointing me towards the Loader Control Valve, but I don’t understand how this valve operates. Is it possible that when the extend function is activated (arms being raised), the retract port is open back to the tank (creating no back pressure on the retract port), but when the retract function is activated (arms being lowered), the extend port is not open back to the tank, but instead is pressurized. The retract port then has to produce more pressure to overcome the back pressure, causing the retract port at the cylinder to be 1,500 psi to 3,400 psi (depending upon the force being applied to the joy stick) and the pressure at the extend port of the cylinder to be 500 to 1,500 psi?
I would greatly appreciate any feedback you guys could provide on the following questions:
1) Can one of the two lift cylinders be removed and the hoses capped and the remaining cylinder should still work fine?
2) Are the lines to the cylinder ports connected together via a Y or Tee? If this is correct, how could I have higher pressure on one arm cylinder vs. the other, unless there is blockage in one of the lines. If one line was blocked, it should behave that way all the time, which it doesn’t.
3) When the extend port on the Lift Control Valve is activated should the retract port open to the return tank (zero pressure in line) and when the retract port on the Lift Control Valve is activated should the extend port open to the return tank (zero pressure in line).
4) If the above assumptions are correct, any idea as to why it is not working correctly and what I should look at next?
Thanks!
