New Holland L 555

[cha9969]

I have a New Holland L 555 (serial # 713285, think 1987 model) that has bucket tilt problem, this model only has one cylinder for the bucket. I have pulled control valve and had it checked at hydraulic shop and it checked OK. I put a pressure gauge in the bucket cylinder hose line on each side and I have 3000 psi on both sides of cylinders lines when I move the control pedal in either direction. The spool control valve has a pressure regulator which should limit the pressure to 1850 lbs on the cylinders, as indicated in the service manual. The boom cylinders work fine and the drive works fine. The question I have is can the increased pressure on the bucket cylinder spool valve cause this problem. Thanks in advance if someone has some ideas on this.

 

[jerry]

This should be in the New Holland section but someone will move it.
What exactly is the problem? It sounds like you have 3000# on both ports of the cylinder when the valve is operated and held in one position? Something is goofy if you have pressurized oil in both lines when ever the valve is operated.

 

[OldMachinist]

This should be in the New Holland section but someone will move it.
What exactly is the problem? It sounds like you have 3000# on both ports of the cylinder when the valve is operated and held in one position? Something is goofy if you have pressurized oil in both lines when ever the valve is operated.

Cylinder piston seal is blown or the nut that holds the piston on the rod has come loose.

 

[cha9969]

Cylinder piston seal is blown or the nut that holds the piston on the rod has come loose.

Thanks for the replies. To date the trouble shooting sequence is as follows. I pulled the control valve and cylinder and took it to hydraulic shop. The cylinder was attached to control valve and operated at 1500 PSI. All operations of valve and cylinder where verified to operate properly. All hydraulic lines were traced out on the tractor and are going to proper locations using hydraulic schematic in maintenance manual. My current thinking is that the pressure regulator in the control valve is causing this problem.

 

[jerry]

Thanks for the replies. To date the trouble shooting sequence is as follows. I pulled the control valve and cylinder and took it to hydraulic shop. The cylinder was attached to control valve and operated at 1500 PSI. All operations of valve and cylinder where verified to operate properly. All hydraulic lines were traced out on the tractor and are going to proper locations using hydraulic schematic in maintenance manual. My current thinking is that the pressure regulator in the control valve is causing this problem.

It would have to be something unusual, if the cylinder piston seals were bad the oil would just bypass. The build up of pressure on the outgoing port shows restriction somewhere on the return line. When they tested the valve and cylinder maybe they should have cranked up the pressure to check the regulator. Although you probably did not take the hoses in with the cylinder? Could it be a collapsed or plugged hose? Is this regulator in the valve or where it controls pressure to all the cylinders?

 

[jerry]

It would have to be something unusual, if the cylinder piston seals were bad the oil would just bypass. The build up of pressure on the outgoing port shows restriction somewhere on the return line. When they tested the valve and cylinder maybe they should have cranked up the pressure to check the regulator. Although you probably did not take the hoses in with the cylinder? Could it be a collapsed or plugged hose? Is this regulator in the valve or where it controls pressure to all the cylinders?

I could not see a listing for a l555 on messick's site but the l554 does show a flow control valve, could that be it?

 

[Mike10]

Thanks for the replies. To date the trouble shooting sequence is as follows. I pulled the control valve and cylinder and took it to hydraulic shop. The cylinder was attached to control valve and operated at 1500 PSI. All operations of valve and cylinder where verified to operate properly. All hydraulic lines were traced out on the tractor and are going to proper locations using hydraulic schematic in maintenance manual. My current thinking is that the pressure regulator in the control valve is causing this problem.

What exactly is the problem with the bucket circuit? Will the bucket not tilt? Will the bucket leak down? It is unclear from your post what problem you are trying to fix.

 

[cha9969]

What exactly is the problem with the bucket circuit? Will the bucket not tilt? Will the bucket leak down? It is unclear from your post what problem you are trying to fix.

Thanks For the reply: The problem is that the bucket will not tilt in either direction. In trouble shooting process, I have also disconnected the linkage to the control valve and move the spool control valves by hand and bucket will still did not move. I have checked that hoses to bucket cylinder for proper flow. I disconnected hoses with the engine running and move the foot control and I have high pressure flow on each line. I got no indication that hoses were restricted.

 

[Mike10]

Thanks For the reply: The problem is that the bucket will not tilt in either direction. In trouble shooting process, I have also disconnected the linkage to the control valve and move the spool control valves by hand and bucket will still did not move. I have checked that hoses to bucket cylinder for proper flow. I disconnected hoses with the engine running and move the foot control and I have high pressure flow on each line. I got no indication that hoses were restricted.

I would tee a pressure gauge into the front port of the bucket cylinder so the hose is still connected and you can get a pressure reading. Then remove the rear hose from the cylinder and install a third hose to the rear port of the cylinder so you can direct the oil flow into a bucket. Cap the original hose. Start the engine and try to curl the bucket back. One of the following should occur. You build high pressure and the bucket does not move, defective cylinder. You build low pressure and cylinder does not move, if oil is running into the bucket from the rear port with no bucket movement then the seals are blown or the piston is off the rod of the cylinder. If oil is not running out of the rear port with no bucket movement then you have a problem with the control valve. If bucket moves then you have a restriction in the rear cylinder hose or control valve. You can move the gauge to the rear port and do the same checks with the front port open.

 

[jerry]

I would tee a pressure gauge into the front port of the bucket cylinder so the hose is still connected and you can get a pressure reading. Then remove the rear hose from the cylinder and install a third hose to the rear port of the cylinder so you can direct the oil flow into a bucket. Cap the original hose. Start the engine and try to curl the bucket back. One of the following should occur. You build high pressure and the bucket does not move, defective cylinder. You build low pressure and cylinder does not move, if oil is running into the bucket from the rear port with no bucket movement then the seals are blown or the piston is off the rod of the cylinder. If oil is not running out of the rear port with no bucket movement then you have a problem with the control valve. If bucket moves then you have a restriction in the rear cylinder hose or control valve. You can move the gauge to the rear port and do the same checks with the front port open.

Now that we know it wont move either way I would think the piston has come off the end of the rod. If so when you replace it be sure to use a new locking nut and Loctite. If the threads are poor replace or rebuild because if that nut comes off with a full bucket of rocks a lot of them may land on you.

 

[cha9969]

I would tee a pressure gauge into the front port of the bucket cylinder so the hose is still connected and you can get a pressure reading. Then remove the rear hose from the cylinder and install a third hose to the rear port of the cylinder so you can direct the oil flow into a bucket. Cap the original hose. Start the engine and try to curl the bucket back. One of the following should occur. You build high pressure and the bucket does not move, defective cylinder. You build low pressure and cylinder does not move, if oil is running into the bucket from the rear port with no bucket movement then the seals are blown or the piston is off the rod of the cylinder. If oil is not running out of the rear port with no bucket movement then you have a problem with the control valve. If bucket moves then you have a restriction in the rear cylinder hose or control valve. You can move the gauge to the rear port and do the same checks with the front port open.

I have put a tee with pressure gauge at the bucket cylinder on each port. I have the same pressure on each side of the cylinder. If I remove one line from the cylinder and plug it while running the cylinder discharge side into a bucket, I can move the cylinder in or out depending on the line. I watched the catch bucket for cylinder bypass and could not detect cylinder bypassing. The bucket will not move if both hoses to cylinder is connected, but will move if one cylinder hose is disconnected. Thanks For the Suggestions.

 

[Mike10]

I have put a tee with pressure gauge at the bucket cylinder on each port. I have the same pressure on each side of the cylinder. If I remove one line from the cylinder and plug it while running the cylinder discharge side into a bucket, I can move the cylinder in or out depending on the line. I watched the catch bucket for cylinder bypass and could not detect cylinder bypassing. The bucket will not move if both hoses to cylinder is connected, but will move if one cylinder hose is disconnected. Thanks For the Suggestions.

The next step is going to be the messy step. remove one line from the control valve and see if the bucket will move. If it does the control valve has a problem. Did you disassemble the valve when you had it out? You might also remove the two fittings from the top of the control valve which go to the bucket and see if someone put an orifice under one of the fittings. If so the orifice might be plugged. There should be an orifice on the boom side of the valve but none on the bucket side.

 

[cha9969]

The next step is going to be the messy step. remove one line from the control valve and see if the bucket will move. If it does the control valve has a problem. Did you disassemble the valve when you had it out? You might also remove the two fittings from the top of the control valve which go to the bucket and see if someone put an orifice under one of the fittings. If so the orifice might be plugged. There should be an orifice on the boom side of the valve but none on the bucket side.

When I removed the control valve it was disassembled and inspected. No apparent damage to spools in the control valve or control valve body. The control valve was placed on hydraulic test stand with bucket cylinder attached and operated at 1500 psi. On the test stand the bucket cylinder worked properly along with control valve. No orifice in either port of bucket side of control valve. Thanks for the continued help.