Boom lift Drive Wheels torque fade

[TVA]

The only thing you can remove is a flow divider - but it will make the spinning situation even worse.
Good idea to measure pressure right at the motors because counterbalance valves could be miss adjusted, but I doubt it!

If you will take out everything the fluid will be returning to tank freely and you will not be able to get off of a parking breaks.

 

[Ronray]

The smaller spools slide freely both directions inside the large sleeve spool and I did not see any scratches on the inside of that large sleeve.

Actually I have the swash plates lever set to the maximum at 18 degrees on both Motors which allowed the right wheel 2 have more torque and keeps spinning digging deeper into the ground, but the left wheel just stopped after a few inches.

Are the counterbalance valve's the ones with the really heavy duty springs in the pictures I uploaded on Wednesday that also had the Allen screws for adjustment?

Also, just FYI, in the pictures I uploaded on Wednesday of the small spools that you told me I could lift out with needle-nose pliers, the picture looks like there is one rubber o-ring on each spool, but there are actually two o rings side by side in the groove, one a little bit larger than the other one. They do fit snugly into the cylinder bore.

 

[TVA]

Yes, counterbalance valve is the ones with heavy springs. You need to build up the pressure before they allow fluid to go through them. On the manlift everything is counterbalance, I think it’s a safety issue. I suggest you read up on them.

 

[TVA]

It’s also could be something simple like flapper inside tho hose.

 

[Ronray]

Here is another consideration, in this picture of one of the connectors into the manifold from one of the large hoses going to the problem will, there was a little bit of corrosion so I wire wheeled it and was left with a little bit of pitting in the metal. I put a cap on it and submerged in water and applied air pressure as a test and it did not seem to be leaking air back through the threads. But I'm not sure what 2500 lb of hydraulic fluid pressure would do.

 

[Ronray]

I did not know that these hoses could have a flapper valve inside them. I will have to take a look...

 

[TVA]

I did not know that these hoses could have a flapper valve inside them. I will have to take a look...

Not flapper valve, flapper means deteriorating rubber and piece peeling off the wall and blocking the flow.
That’s a JIC fitting and it can only lleak to outside.

 

[Ronray]

Okay thanks. I will see if I can inspect the insides of those hoses and see what they look like. And maybe even switched them if I can.
So then I assume that even if that jic fitting was leaking it would not affect the wheel motor function.
Here's another picture of that spool with the two little O-rings in the same groove. Any thoughts on 2 o rings vs 1 larger o ring in the same Groove?

 

[TVA]

I’ve seen it, one is O-ring the other is back up ring.

You know very often disassembly and reassembly fixes things, something that was stuck gets free or something that was plugged gets cleaned.
If you don’t see any damages, make sure to clean all the small passages blow everything with compressed air and reassemble, see if it will start working.

If not we will start diagnosing from there.

 

[TVA]

Please read up on back up rings and O-ring extrusion. Size of the o-ring should be determined by groove size and application: dynamic or static, face seal, radial etc.

 

[Ronray]

Thanks TVA!
As far as blowing everything out, what do you think about dipping the entire block in a bowl of gasoline and swishing it out then blowing it out with compressed air then dipping the block back into hydraulic fluid right away?

Or what about just blowing out the block with high pressure water and then blowing it with compressed air and then dipping it into the hydraulic fluid?

Or this just occurred to me, plug up all but two holes on the manifold and blow it from one of the open holes so the air exits the other open hole, then close off the exit open hole and reopen another exit hole and blow it out from the original open hole, and just repeat that procedure for every connection point to the manifold?

 

[TVA]

I usually take the whole thing apart and blow everything out, and if something is not blowing out reserve to more drastic measures!

 

[Ronray]

Thanks TVA!

 

[TVA]

Another, kinda silly thing to check is weather your wheels turn the same direction. You see motors are swapped, and the hoses must be swapped too to go the same direction, it happens that people when replacing hoses do not put them back on correctly. So the hose to let’s say go forward should be on the left side on the left motor then to go forward on the right motor it should be on opposite side.

 

[Ronray]

Thanks TVA. The wheels are turning the same direction. I'm getting ready to blow out the manifold with compressed air, and my plan was to initially blow the compressed air in the direction of the Inlet source of the hydraulic fluid, thinking that if something was lodged , it would come out easier in the direction it came from.

 

[Ronray]

Hi TVA. So I completely disassembled the valve manifold and blew it out where is compressed air and I have two questions,

1. One of the two large Inlet hoses seems to have a restriction between the inlet and the pressure compensating large divider spool cylinder, and so I am wondering if possibly it was designed that way to keep the wheel motors from going too fast in reverse? And I'm assuming that one large inlet hose is for forward and the other one is for reverse?

2. I also discovered 2 more little sleeves with rubber O-rings in the 2 smaller spool cylinders in line with the heavy duty springs however one of the little sleeves was reversed, and I am not sure which way the little sleeves are supposed to be pointing. I am guessing that it was reassembled at one time improperly. See attached picture. One end of the sleeve is beveled and the other end next to the O-rings is flat. Should the bevel end be facing the little piston? The service parts manual does not show the valve manifold parts. It just shows the entire assembly.

 

[TVA]

Are those sleeves going in to blind hole or they have a plug on the other side?

 

[Ronray]

No plug on the other side, but there is a hole on the other side and the thin rod portion of the piston in the attached picture goes through the sleeve and contacts the piston on the heavy duty spring side of the little sleeve

 

[TVA]

All of the sudden got really busy!!! Look for position in which that sleeves o rings will not block the passages, also see if bore has special place for o rings will slide tighter in to. I’ll get back as soon as you can.

 

[Ronray]

Wow, great advice. I didn't even know that sleeve was there until I accidentally saw the sleeves o rings in a side passage opening. So that would mean that this slave was apparently previously inserted upside down accidentally.

What about my comment on the one large entry hose into the manifold appearing to be blocked? Should both entry hoses be able to carry the same volume of fluid to the pressure compensating divider spool cylinder?
I assume that 1 hose is for foreword rotation and the other hose is for backwards rotation of the wheels?