Problem with curl cylinder?

[radman1]

Tried my 5610 TC with 36" tree spade today. This is the first time I tried it on the TC. I could lift the ball of dirt but the curl cylinder would not hold. As I lifted the spade, the tilt cylinder would extend as I lifted. Never could lift the far end of the spade. I had never seen any cylinder do that before. I assume the oil is bypassing in the hydraulic control valve rather than in the seals of the cylinder. Is that possible? Would a check valve on the cylinder stop the forced extension? With the spade not filled with dirt, the spade would tip/settle rather quickly, faster than I believe it should.

 

[J_J]

Tried my 5610 TC with 36" tree spade today. This is the first time I tried it on the TC. I could lift the ball of dirt but the curl cylinder would not hold. As I lifted the spade, the tilt cylinder would extend as I lifted. Never could lift the far end of the spade. I had never seen any cylinder do that before. I assume the oil is bypassing in the hydraulic control valve rather than in the seals of the cylinder. Is that possible? Would a check valve on the cylinder stop the forced extension? With the spade not filled with dirt, the spade would tip/settle rather quickly, faster than I believe it should.

Does the curl cylinder have full range, and does it go to the relief mode when you are at the end stops. It almost sounds like a float valve is activated. Are the hoses connected correctly. Perhaps the curl cylinder is switched with the lift cylinders at the valve.

 

[radman1]

The cylinder otherwise behaves normally. Full extension and retraction. Goes into relief at both ends of range. Haven't changed any hoses, fluids ect. The joystick functions normally. Unit is about 6 months old.

 

[radman1]

Talked with dealer this am. He thinks it is more likely the cylinder rather than the control valve, but could be either. May have blown a seal in the cylinder or the nut on the cylinder ram could be loose allowing oil to bypass.

 

[J_J]

It would seem like if the cylinder goes into relief on push and pull, then it should not be a cylinder problem. In your first post you said that you could not lift the tip of the tree spade, but if the cylinder is working normally with relief. Was the cylinder extended when you went into the ground, say at a 45 degree angle? Something is not making sense here.
Can you put the tip of the spade on the ground and raise your front wheels by using curl cylinder, and will it stay there ?

 

[DEWFPO]

After we changed out a hose, I was curling up, it stopped and started to 'uncurl' even though I was still trying to curl up and then it finally began to curl up again. I attributed that to air in the system since we had just changed a hose.

My curl cylinder will not hold pressure well, even with the engine running the curl will drop flat within 15 minutes. A royal PITA when driving down the road. I'm really wondering if there's a defect somewhere in the curl cylinder hydraulics. My 5600 is only a few months old.

DEWFPO

 

[J_J]

After we changed out a hose, I was curling up, it stopped and started to 'uncurl' even though I was still trying to curl up and then it finally began to curl up again. I attributed that to air in the system since we had just changed a hose.

My curl cylinder will not hold pressure well, even with the engine running the curl will drop flat within 15 minutes. A royal PITA when driving down the road. I'm really wondering if there's a defect somewhere in the curl cylinder hydraulics. My 5600 is only a few months old.

DEWFPO

There is no reason for a cylinder to move from the position that you set it, other than the quality of the valve, etc. There is a leak somewhere. Extend the cylinder and listen for the relief to come on. and retract the cylinder and listen for the relief to cut in. That tells you the pump is putting out the pressure and if you had a gage, you would know the relief pressure. Fluid is being moved somewhere, unless all the air has not been purged. Some of the guys on here say that the air should be purged after a couple of cycles, but there may be voids that the air will never come out unless the cyl is rotated so that the cylinder fittings are at the highest point. There are times when you are compressing fluid and air, and in effect is acting like an accumulator, so when you release the valve, the compressed air will put a force on the piston. I don't believe the fluid will absorb the air trapped inside the cyl. It has to be bleed off in some way. Could be wrong, what say the others.

 

[radman1]

It would seem like if the cylinder goes into relief on push and pull, then it should not be a cylinder problem. In your first post you said that you could not lift the tip of the tree spade, but if the cylinder is working normally with relief. Was the cylinder extended when you went into the ground, say at a 45 degree angle? Something is not making sense here.
Can you put the tip of the spade on the ground and raise your front wheels by using curl cylinder, and will it stay there ?

With no dirt in the tree spade, the curl cylinder will tip the front of the spade up and down and not go into relief. With the spade on the ground the curl cylinder is in the midportion of its stroke. When I had dirt in the spade, the the boom could lift the back of the spade. As the boom lifted the back of the spade higher, the curl cylinder would extend at least several inches from the weight of the spade/dirt. It would extend without any input/movement from the hydraulic control. It seems like the sheer weight of the lift was causing oil in the curl hydraulic circuit to bypass somewhere.
I can raise my front wheels with the curl cylinder when tipping the spade down and it will stay there.

 

[radman1]

My curl cylinder will not hold pressure well, even with the engine running the curl will drop flat within 15 minutes. A royal PITA when driving down the road. I'm really wondering if there's a defect somewhere in the curl cylinder hydraulics. My 5600 is only a few months old.

DEWFPO

I think yours is defective and has a leak either in the valve or cylinder. It should not leak down that fast with a normal load on the cylinder. Mine may have been overstressed. Mine now will tip down faster than before but still doesn't sound as bad as yours.
Dealer told me a way to check if the problem is in the cylinder. He recommended removing any attachment from the bobtach. Tip the bobtach back all the way. Remove the hose from the top cylinder and see if any oil come out of the cylinder when the the bobtach is again tipped back by running the hydraulics. If oil comes out, problem is somewhere in the cylinder.
I think your dealer needs to look at yours.

Mine is only 5-6 months old and took it to the dealer today. If its under warranty, I figure it is their problem.

 

[J_J]

What you are doing in this test is to see if you have blown o-rings on the piston in the cylinder, or the shaft has a slight bend in it. You will have to hold the Bobtac back enough to activate the relief, just to see if it will force fluid past the piston, otherwise, it will not take a lot of pressure just to move the attachment. I didn't realize how much pressure it took to raise a bucket with no load, less than a thousand psi on my Power-Trac. You will only see high psi when working the attachment hard, as in full load.

 

[radman1]

Update. TC is still at dealer. So far have not found much wrong. Cylinder is OK. Checking other possible problems in the control valve and relief valve.

 

[DEWFPO]

The mechanic was out to check my curl cylinder yesterday. He wasn't sure what the spec was but thought it was 1.5" movement over 10 minutes or so. Doe anyone know what the actual spec is? Is there a temp spec as well?

Anyway. I was right at that when he checked it but the oil wasn't all that hot. The hotter the oil, the faster the cylinder looses pressure. The cylinder moved about 2" in about 15 minutes. When I'm blowing snow for 2 hours and really working the hydraulics, it drops even faster.

He checked the cylinder itself by getting the hydro oil warm, disconnecting the return pipe, plugging both ends and putting curling the cylinder in the max position for several minutes at a time, in both directions. He said if there was a seal leak, it would push the cylinder out. It didn't so he concluded the cylinder was fine.

He said the problem seems to be with the control valve or relief valve, I can't remember which one he said. It's under the joystick and it has rubber seals. He said some pressure will be lost past the spindle valve, but it appears my rubber seals are leaking pressure. I hope he's right. He didn't have a seal kit with him so he's going to have to come back.

DEWFPO

 

[radman1]

The mechanic was out to check my curl cylinder yesterday. He wasn't sure what the spec was but thought it was 1.5" movement over 10 minutes or so. Doe anyone know what the actual spec is? Is there a temp spec as well?

Anyway. I was right at that when he checked it but the oil wasn't all that hot. The hotter the oil, the faster the cylinder looses pressure. The cylinder moved about 2" in about 15 minutes. When I'm blowing snow for 2 hours and really working the hydraulics, it drops even faster.

He checked the cylinder itself by getting the hydro oil warm, disconnecting the return pipe, plugging both ends and putting curling the cylinder in the max position for several minutes at a time, in both directions. He said if there was a seal leak, it would push the cylinder out. It didn't so he concluded the cylinder was fine.

He said the problem seems to be with the control valve or relief valve, I can't remember which one he said. It's under the joystick and it has rubber seals. He said some pressure will be lost past the spindle valve, but it appears my rubber seals are leaking pressure. I hope he's right. He didn't have a seal kit with him so he's going to have to come back.

DEWFPO

I don't quite understand the specs for leakage. At first my dealer said it checked out fine and within Bobcats specs. However, I asked him how he checked it. It was just with the bucket on the TC. Told him, when I use my sweeper, I can visibly watch the broom tip down and it wasn't like that before. He did say it should not do that with a broom on the front. I can't be tipping my broom back every 1-2 minutes because of the problem.

 

[DEWFPO]

I don't quite understand the specs for leakage. At first my dealer said it checked out fine and within Bobcats specs. However, I asked him how he checked it. It was just with the bucket on the TC. Told him, when I use my sweeper, I can visibly watch the broom tip down and it wasn't like that before. He did say it should not do that with a broom on the front. I can't be tipping my broom back every 1-2 minutes because of the problem.

This supposed 'spec' is ~1.5 " of cylinder movement over 10 minutes of time (if that is the correct spec.). Mine moves faster when hot so there should be some hydro fluid temp spec as well. In any case, the mechanic is trying to say 'it is in spec (barely) and I am trying to push him to do something about it because it's unacceptable to me and can be down right dangerous if I forget to pull it up often when driving down the road.

DEWFPO

 

[J_J]

This supposed 'spec' is ~1.5 " of cylinder movement over 10 minutes of time (if that is the correct spec.). Mine moves faster when hot so there should be some hydro fluid temp spec as well. In any case, the mechanic is trying to say 'it is in spec (barely) and I am trying to push him to do something about it because it's unacceptable to me and can be down right dangerous if I forget to pull it up often when driving down the road.

DEWFPO

Why not take a video and tell the mechanic /owner that you have tried to get it fixed, and they all procrastinate. Then send the video to the president of Bobcat.

 

[radman1]

This supposed 'spec' is ~1.5 " of cylinder movement over 10 minutes of time (if that is the correct spec.). Mine moves faster when hot so there should be some hydro fluid temp spec as well. In any case, the mechanic is trying to say 'it is in spec (barely) and I am trying to push him to do something about it because it's unacceptable to me and can be down right dangerous if I forget to pull it up often when driving down the road.

DEWFPO

1.5" of cylinder movement in 10 minutes makes a big difference on how far an approved attachment like a broom tips down. Brooms are not designed to run with much weight on the bristles and most of the weight hangs far out front. My TC has been in the shop 10 days and now they are checking out a few things in the spool valve. They are waiting on some parts.
Yours seems much worse than mine. I have a check valve. I may just install it if they can't/won't fix it. I may just install the check valve anyway. I want to use my 11' manlift on a job in a few months. I can't have any significant tipping when it is in the air.
The boom lift cylinder is very stable.

 

[DEWFPO]

I haven't measured my boom/lift cylinder but I haven't noticed any obvious problems.

The curl problem is fairly obvious when you use pallet folks or the bucket to lift something up and hold it there while you work on whatever it is you are lifting.

If you install the check valve, let me know if it solves your problem. I'm going to continue to try to get the dealer to solve this but if he can't I will.

DEWFPO

 

[radman1]

I haven't measured my boom/lift cylinder but I haven't noticed any obvious problems.

The curl problem is fairly obvious when you use pallet folks or the bucket to lift something up and hold it there while you work on whatever it is you are lifting.

If you install the check valve, let me know if it solves your problem. I'm going to continue to try to get the dealer to solve this but if he can't I will.

DEWFPO

Dealer warned me that I may not like how the tilt cylinder may work with the check valve. I have used them on TNTs for 2 different tractors and think they work great. He thinks I may not like how the controls work with check valve and it may chatter. I have not noticed any problems on my other cylinders. He had a customer use one on a all terrain construction lift and it did not work well. I have 2 Vickers double piloted check valves that I bought from Ebay. 3000 psi with 12gpm flow. Just need to get a few other fittings and hoses.

 

[J_J]

Dealer warned me that I may not like how the tilt cylinder may work with the check valve. I have used them on TNTs for 2 different tractors and think they work great. He thinks I may not like how the controls work with check valve and it may chatter. I have not noticed any problems on my other cylinders. He had a customer use one on a all terrain construction lift and it did not work well. I have 2 Vickers double piloted check valves that I bought from Ebay. 3000 psi with 12gpm flow. Just need to get a few other fittings and hoses.

Did you ever try another valve as a test valve to see if the cylinders does the same thing. In your parts manual, does it say that the spool has o-rings, if so, pull that out and replace the o-rings.

 

[SPYDERLK]

With no dirt in the tree spade, the curl cylinder will tip the front of the spade up and down and not go into relief. With the spade on the ground the curl cylinder is in the midportion of its stroke. When I had dirt in the spade, the the boom could lift the back of the spade. As the boom lifted the back of the spade higher, the curl cylinder would extend at least several inches from the weight of the spade/dirt. It would extend without any input/movement from the hydraulic control. It seems like the sheer weight of the lift was causing oil in the curl hydraulic circuit to bypass somewhere.
I can raise my front wheels with the curl cylinder when tipping the spade down and it will stay there.

I know further on the dealer says the cyl checks out, but from the above I think the nut on the piston end of the ram is loose.
larry