What are all the possibilities....

[futuresweets10]

Most of you have probably seen my other threads about the FEL bucket on my back hoe not tilting. I took the valves off and had a local shop re-build them. That didnt fix the problem so I took the cylinder off took it apart and everything is good inside the cylinder. I plan to go to the shop on monday and request on site service to correct the problem at no charge to me. If they were to find the problem and it isnt in the valves I would be wiling to pay for their time.

Here is what I ask of you guys. If the cylinder is good, what other problems could POSSIBLY cause the FEL tilt to not work at all other than the valves. I want to go over everything I can this weekend so that when I go back to them I am 100% sure that the problem resides in the valves that they already re-built.

 

[AKKAMAAN]

Here is what I ask of you guys. If the cylinder is good, what other problems could POSSIBLY cause the FEL tilt to not work at all other than the valves. I want to go over everything I can this weekend so that when I go back to them I am 100% sure that the problem resides in the valves that they already re-built.

If the piston is pushed in (retract) while bucket is dropping down....following is possible...
1. external leak in gland seal and hose fittings
2. internal leak in piston seal, which means that the volume the piston rod is displacing, is subject to internal leak some where in the control valve, either the spool or some work port valving.
3. if piston seal do not leak, the entire capped side volume of cylinder is subject to internal leaking the same way as #2 above. The void of oil on the rod side will then, either be vacuum, air sucked in through gland seal, oil sucked in through spool leakage or through some work port valving.

Of course there can be several of the above errors, to co-operate, making this fault.

So if this cylinder piston is retracting, and no external leaks.....there is something leaking in the control valve PERIOD!!!!

I think J-J's suggestion is OK, about installing a ball valve on the capped side of the cylinder, and shut it off when bucket is flat on the ground. Lift and see what happens. Add a second ball valve (3 way) on the rod side, and do the same test. Take a video over the whole procedure, showing the ball valves and so on....

That should be proof that control valve is in fault....

 

[tlbuser]

Leave rod end off and try moving cylinder. If rod extends and retracts, valving and cylinders should be ok. Hook rod ends back and see if buckets moves, linkages may be connected wrong. Could you connect a guage at the cylinder ends to see pressures?

 

[EddieWalker]

How did you determine the cylinder is good? Then thousands of pounds of pressure, a worn seal can hold just fine without pressure, but leak like crazy under pressure. Again, how do you know it's not a seal?

How much pressure do you have on the line?

The valve either allows the fluid through, or holds it back. It's real easy to see if it's working with a gauge. Cracking the line and seeing fluid come out is not the same thing as being able to tell if there is 100 psi or 1,000psi. While 100psi will shoot fluid out under pressure for a very long distance, it's not enough pressure to do anything.

I'm at a loss as to how you are testing the problem and how you are reaching your conclusions. Have you considered hiring sombody to do this for you?

Good luck
Eddie

 

[futuresweets10]

How did you determine the cylinder is good? Then thousands of pounds of pressure, a worn seal can hold just fine without pressure, but leak like crazy under pressure. Again, how do you know it's not a seal?

How much pressure do you have on the line?

The valve either allows the fluid through, or holds it back. It's real easy to see if it's working with a gauge. Cracking the line and seeing fluid come out is not the same thing as being able to tell if there is 100 psi or 1,000psi. While 100psi will shoot fluid out under pressure for a very long distance, it's not enough pressure to do anything.

I'm at a loss as to how you are testing the problem and how you are reaching your conclusions. Have you considered hiring sombody to do this for you?

Good luck
Eddie

I took the cylinder apart and inspected everything.... I was also told to take one line off and then apply pressure to the other one and see if fluid comes out the open end of the cylinder...

 

[EddieWalker]

I've rebuild dozens of cylinders. I can only think of a couple where it was obvious to look at it and know what went wrong. Most of the time, it looks fine.

What were you looking for and how do you know the seals are fine?

Eddie

 

[mmurphy]

I think the cheapest and easiest test would be what JJ suggested. Keep in mind, do not put full pressure unless you are going to use pressure rated fittings. As Eddie also pointed out, most of time can not see a bad seal.

 

[futuresweets10]

I've rebuild dozens of cylinders. I can only think of a couple where it was obvious to look at it and know what went wrong. Most of the time, it looks fine.

What were you looking for and how do you know the seals are fine?

Eddie

Well, I guess I dont know they are fine.... I was going off of appearance and feel.... I am going to go buy new seals today and then put the cylinder back together.... If this does not fix the problem the machine is going to the shop.

 

[J_J]

I took the cylinder apart and inspected everything.... I was also told to take one line off and then apply pressure to the other one and see if fluid comes out the open end of the cylinder...

This test will work. Did you do this, and did you pressurize both ports. You have to let the cyl drain all the fluid out of the open port, and then pressurize the other port.

 

[wdchyd]

I'm at a loss as to how you are testing the problem and how you are reaching your conclusions. Have you considered hiring sombody to do this for you?

Good luck
Eddie

:mur:......

 

[futuresweets10]

Well, I just got in from putting the re-built cylinder back on the machine.... Problem is the same as it was before.... I guess I will go to the hydraulic shop Monday and see what they suggest and see if they will warrant the rebuild they did on the valves. Im willing to bet that because I did the removal and re installation the first time around they will make me do the same again....

 

[CurlyDave]

How much was the original valve rebuild?

Maybe it is my old age and suspicion, but letting the people who rebuilt the valves diagnose what is wrong now, is almost never going to lead to a diagnosis of a bad rebuild, especially if they have to fix it on their own nickel.

I would probably be willing to invest 20-30% of the initial rebuild cost in getting an independent diagnosis of the problem. I some other mechanic says the rebuild is faulty, I would be asking the shop for both another rebuild, and the cost of the mechanic.

 

[futuresweets10]

How much was the original valve rebuild?

Maybe it is my old age and suspicion, but letting the people who rebuilt the valves diagnose what is wrong now, is almost never going to lead to a diagnosis of a bad rebuild, especially if they have to fix it on their own nickel.

I would probably be willing to invest 20-30% of the initial rebuild cost in getting an independent diagnosis of the problem. I some other mechanic says the rebuild is faulty, I would be asking the shop for both another rebuild, and the cost of the mechanic.

I agree with that 100%, but if I take it somewhere else im afraid the original shop will just say the second shop is wrong or lieing, or that I messed up what they did before taking it to the second shop. The rebuild was about 300, but it was only that because I took the valves off myself. I am at the point now where I am done messing with it. The ONLY other place I could take it is the CAT dealer, and I know they are going to be high. Either way I am going to have to pay someone to transport, and the CAT dealer is MUCH closer so it might all be a wash.

I know if I take it to CAT and they tell me the original rebuild is the issue I am going to demand a refund from the first place.

 

[tlbuser]

I know if I take it to CAT and they tell me the original rebuild is the issue I am going to demand a refund from the first place.

Rather than paying a haul fee and try to DEMAND anything, call the hydraulic shop and ask if they will provide some onsite assistance. Sounds like you decided the valve was bad and dropped it off for an overhaul. How are they the bad guys for doing what you asked?